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...... eram1cs Christoph Hammerle Irena Sailer Andrea Thoma Gianni Halg Ana Suter Christian Ramel
cu 0 · .I 0 0 -
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B Annen, G Benic, A Feher, R Glauser, A Hagmann, S Hick ling, C Holderegger, R Jung, H Klaj n er t, 0 Loeffel, S Merki, D Polly, P Ruhstaller, D Siegenthaler, M Stanc o, D Thoma, A Trottmann, S Windisch, D Yaman, A Zembic
Quintessence Publishing Co Ltd London, Berlin, Chicago, Tokyo, Barcelona, Beijing, Istanbul, Milan, Moscow, New Delhi, Paris, Prague, Sao Paulo, Seoul and Warsaw
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The authors are grateful to the participating dental technicians for the excellent restorations they provided and for their consistently good teamwork. We would especially like to thank Walter Gebhard (Geb hard AG, Zurich), Bertrand Thievent (Bertrand Thievent AG, Dental Laboratory, Zmich), Arnold Wohlwend (Wohlwend Innovative Dental Technik, Zurich), and KBTM Intern Dental Laboratory (Director: Ana Suter). Special thanks also to Heinz Luthy for his contributions regard ing the technical aspects of dental ceramic materials.
Title of the original German edition: Dentale Keramiken Aktuelle Schwerpunkte fur die Klinik © 2008 by Christoph Hammerle
Quintessence British Library Cataloguing in Publication Data Dental ceramics : essential facts for cosmetic dentists I. Dental ceramics I. Hammerle, Christoph 617.6' 95
ISB}J:9781850971818 © 2008 by Christoph Hammerle
Quintessence Publishing Co, Ltd, Grafton Road, New Malden, Surrey KT3 3AB, Great Btitain
www.quintpub.co.uk
All rights reserved. This book or any part there of may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written petmission ofthe publisher. Editing: Quintessence Publishing Co, Ltd, London Translation: Suzyon O'Neal Wandrey, Berlin Layout and production: Quintesssenz Verlags-GmbH, Berlin Printing and binding: AZ Druck und Datentecbnik GmbH, Kempten Ptinted in Gem1any
IV
Most dentists' offices are well-stocked with scientific journals and textbooks. However, practising dentists often find it hard to wade through the plethora of dental literature in order to locate the informa tion they require or to find the advice they need in a reasonable amount of time. This book focuses specifically on current issues in contemporary ceramic dentistry. Dental Ceramics - Essential Aspects for Clinical Practice is designed as a quick reference guide. lt provides practising dentists the specific information they need to manufacture ceramic restorations for their patients. Topics covered include ceramic veneers, single crowns, fixed partial dentures, and implant restora tions. Related subjects, such as restoration of non-vital teeth and external bleaching, are also described. The text is concise and clear, providing step-by-step instructions and numerous photographs and diagrams to further elucidate the clinical procedures. "Dental Ceram ics" is a valuable resource for practising dentists as weJJ as for dental students. Thanks to the efforts of dedicated dental clinicians, laboratory technicians and researchers, it has been possible to compile a book that conveys the core principles, background information and proce dures relevant to the fabrication of dental ceramic restorations in a readily comprehensible and attractive format, making this book a valuable reference source for dental practice. Christoph Hammerle
v
Prof Dr Christoph Hammerle Clinic Director E-mail:
[email protected] Dr Irena Sailer Senior Consultant E-mail: irena
[email protected] .ch Dr Gianni Halg Senior Consultant E-mail:
[email protected] Dr Christian Ramel Senior Consultant E-mail: christian.ra
[email protected] .ch Clinic for Crown and Bridge Prosthodontics, Partial Prosthodontics and Dental Materials Science Center for Dental, Oral and Maxillary Medicine University of Zurich Plattenstrasse 11, CH-8032 Zurich
Ana Suter E-mail:
[email protected] Dental Technician Haslihalde 17, CH-8707 Uetikon am See Dr Andrea Thoma E-mail: info@zahnaerzteam kreis.ch Practice for General Dentistry, Oral Surgery, Stomatology and Orthodontics Grosszaun 11, CH-8754 Netstal
VI
1
1.1
Scientific Aspects of Dental Ceramic Materials..... 1 Composition and Classification of Dental Ceramics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .
2
1.2 Physical Properties ......................................................... 6 1.3 Opt ical Properties ........................................................ 10
2
Processing Methods
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2.1 Manual Processing Methods .................................... 14 2.2 Machining ...................................................................... 18
3
Veneers .. ... .... . .... ........ ... .... ............. .
3.1 Indications
.
...
.
.....
.
...
.. ..
....
.
3.2 Contraindications
.
........
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..
..
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..... . . ...... 23 .
.. .. .
........
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.
. 24
.....
....
.
........................................................
24
3.3 Clinical Guidelines ..... ... .... .... ......... .. ... .... .. . .... 25 .
.
.
.
.
.
...
.
.
.
.
3.4 Step-by-step: Clinical Procedures for the Fobrication of Veneers
4
...............................................
26
All-ceramic Single Crowns .. ........... . ..... .... .. . ... 37 ..
...
.
..
.
.
.
4.1 Indications ...................................................................... 38 4.2 Tooth Preparation ........................................................ 39 4.3 Clinical Survival ............................................................ 40 4.4 Clinical and Laboratory Procedures ...................... 44
5
Non-vital Abutment Teeth ............................... ......... 59 .
5.1 Biomechanics of Non-vital Teeth ............................ 60
5.2 Posts
............... . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
61
5.3 Esthetics ........................................................................... 64 5.4 Clinical Procedures ..................................................... 67
6
External Bleaching........................................................ 71
6.1 Introduction ..
. ..... . .. .. .. . .. ... .. .. .. .. . .... .
....
..
6.2 Power Bleaching
.
.
.
.
.
..
..
.
.
.
.
.
.
...
....
.. .. 72 .
..........................................................
73
6.3 Combined Bleaching .................................................. 74 6.4 At-home Bleaching . ... .... ........ ......... ........ ............. 74 .
..
.
.
..
.
6.5 "Over-the-counter" Teeth Whit ening Products ...... 78 VII
Contents
7
7.1
All-ceramic Fixed Partial Dentures .. General Considerations
........
.
....
.. . ...
....
. 81
............................................
82
7.2 Indications ...................................................................... 82 7.3 Tooth
Preparation ........................................................ 84
7.4 Dental Laboratory and Dental Office
Procedure . ..... ... . ........ .... ....... ..... .. .... ....... . ... .... 85 .
7.5
Clinical Survival
7.6 Conclusions
8
.
.
.
.
.
..
.
.
..
.
.
..
Rates ................................................ 90
....................................................................
Bonding of Ceramic Restorations . ..
.. .. .. .
....
...
...
...
.....
91 93
8.1 Adhesive versus Conventional Cementation ...... 94
8.2 Classification of Adhesive Cements . 8.3 Dentin
. . .. .... . 96
....
.
.
...
..
.
Conditioning ....................................................
98
8.4 Ceramic Conditioning .............................................. 100
8.5 Clinical Procedures . .
9
....
.
....
. . .. . .. . . . . .
..
...
...
.
..
.
..
. .
....
...
....
.. 101 .
All-ceramic Implant Supported Restorations...... 113
9.1 Clinical Aspects and Indications ........................... 114 9.2 Advantages of Ceramic
Abutments......................
115
9.3 Disadvantages ............................................................ 115 9.4 Biologic Aspects .. ..
9.5
...
.........
.. . . . . .. . ...
...
.
..
...
...
.. 116
.........
Manufacturers .............................................................
10 Index
VIII
. ..
....
. . . . . . . . . . . . . . . . . . . . . . . . . . ........................... . . . . . . . . . . . . . . . . . . . . . . . . .
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Chapter 1
Scientific Aspects of Dental Ceramic Materials
1.1 Com position a n d Classification of Dental Cera m i cs Conventional dental ceramic materials generally comprised a trans parent, amorphous glassy phase surrounding a crystalline phase in which variable amounts of crystalline particles are dispersed. The addition of crystals improves: Light scatter and opacity and, thus, color adaptation of the transparent glassy phase to the dental hard tissues Stability of the material during firing Control of the coefficient of thennal expansion Resistance of the final restoration to functional stresses in the mouth. •
•
• •
Therefore, the addition of crystals enhances both the esthetic appear ance and the strength of ceramic materials. The larger the crystalline phase, the tougher the ceramic material. Increasing the particle density, the homogeneity of particle distribution, and the strength of the bonds between the crystals and the glassy phase also increases the strength of ceramic materials. At the same time, crystalline reinforcement decreas es the transparency of dental ceramic materials at the expense of . esthehcs8. The newer dental ceramics differ from conventional dental ceram ics in that a larger amount of crystals have been added, leading to a sig nificant increase in material strength. As the addition of crystals also increases opacity, the novel dental ceramics can only be used for fabri cation of substructures for ceramic restorations. Like metal frame works, they must be veneered with a translucent ceramic material. Modem dental ceramics can be classified according to glass phase as follows: Ceramics with a glass phase: - Glass-ceramic - Glass-infiltrated ceramic Ceramics without a glass phase: - Oxide ceramic (polycrystalline) =high-strength ceramic. •
•
2
1.1
1.1.1
Compos ition and Classification of Dental Ceramics
Main Chara cteristics
Glass-ceramics •
• •
•
•
Glassy phase of natural or synthetic feldspar surrounding a crys talline phase (consisting of leucite or lithiwn disilicate crystals in most cases) Multi-phase microstructure (Diagram 1, Figs 1a and 1 b). Indications: (Veneered ceramic restorations) Inlays and onlays Veneers Anterior single crowns Processing: - Mixed to yield a modeling material of elastic consistency - The model piece is subsequently fired to strengthen the material Commercially available systems: Empress I, Empress II and Empress Esthetic systems® (Ivoclar, Liechtenstein) Authentic (anaxdent, Germany) Creapress (Creation, Klema, Austria) Various others.
� Specific characteristics The restorations can be individualized by staining or veneering - No shrinkage occurs during firing.
Diagram 1
Fig 1 a Empress I glass ceramic system as seen under a scanning electron microscope. Note the inho mogeneous structure of the leucite-reinforced matrix.
Fig 1 b Empress II, a lithium disilicate-reinforced glass ceramic, has a structure si g nificantly different from that of Empress I. Note the higher density of the rod shaped crystals. 3
Chapter 1
Scientific Aspects of Dental Ceramic Materials
Glass-infiltrated ceramics •
•
•
•
•
Most glass-infiltrated ceramics have a porous alumina skeleton, which is infiltrated, that is reinforced with (liquid) lanthanum glass They have a multi-phase microstructure (Diagram 2, Figs 2a and2b). Indications: - Substructures for anterior and posterior single crowns. Processing: - Computer-aided milling and subsequent infiltration of indus trially prefabricated blanks Commercially available systems: ln-Ceram® (Vita Zahnfabrik, Gennany)/Alumina (Al203) ln-Ceram® Spinel! (A1203 + Mg02) ln-Ceram® Zirconia (Al203 + Zr02).
-.. Specific characteristics
- The restorations can be individualized by staining or . veneenng There is no shrinkage after modeling. Oxide ceramics !high-performance ceramics) •
Diagram2
4
Oxide ceramics have a pure alumina (Al203) or zirconia (Zr02) crystalline matrix.
Fig 2a ln Cerom Alumino: The presintered core is very porous before gloss infiltra tion. -
Fig 2b ln Cerom Alumino: At f er infiltration, the density -
of the core increases con siderably.
Composition and Classification of Dental Ceramics
l.l • •
•
•
They have a single-phase microstructure (Diagram 3, Figs 3 and 4). Indications: - Alumina/zirconia: cores for anterior and posterior single crowns - Zirconia: anterior and posterior bridge frameworks. Processing: Alumina: computer-assisted milling of industrially manufac tured densely sintered blanks Zirconia: computer-assisted milling of industrially manufac tured pre-sintered or densely sintered blanks. Commercially available systems: a number of CAD/CAM systems are available: Procera® (Nobel Biocare, Sweden) Cercon® (DeguDent, Germany) DCS (DCS Dental AG, Switzerland) CEREC (Sirona, Germany) Lava1M (ESPE, Germany) Various others.
� Specific characteristics The restorations can be individualized by veneering Cores milled from presintered ceramics are subject to shrin kage (approximatly 20%). The choice of the dental ceramic material best suited for an individual case is determined mainly by the physical and optical characteristics of the available materials. '
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Chapter 1
Scientific Aspects of Dental Ceramic Materials
1.2 Physical Properties 1.2.1
Definitions
The strength of ceramic materials is generally described using two variables: flexural strength and fracture toughness. Flexural strength (MPa), or bending strength, is the maximum ver tical load that a material can support without failure (fracture). In material testing, a ceramic sample (usually disk-shaped) is subjected to increasing vertical stress until it cracks or breaks. Different proto cols are used for determination of flexural strength (e.g., three- or four-point bending test). In these tests, the main vertical load, or bend ing stress, is applied to the tensile zone (convex side) of the ceramic sample. The surface quality (polishing, microcracks) of the tensile zone is crucial for the resulting flexural strength. Fracture toughness, or fracture resistance (MPa m1'2), is a measure of the maximum force a material containing a flaw or crack can with stand without enlargement of the crack, when tensile force is applied to the edge of the crack. A simple example illustrates this principle: if a notch (flaw) is made at the top of a piece of wood, it is easier to split the wood with an axe. Continued exposure of the t1awed material to forces slightly or even far below the initial cracking load can result in the gradual propagation of the crack. This slow progression, called subcritical crack growth, is one of the main reasons for the long-term failure of all-ceramic restorations. The higher the fracture toughness ofthe material, the longer it takes for fracture-related failure to occur8• The fracture toughness and flexural strength of various ceramic mate rials are described in Table 1. To prevent clinical failure, "weak" dental ceramic materials, such as glass-ceramics, must be strengthened by means of adhesive cemen tation (cf . ChapterS).
6
1.2 Physical Properties Table 1
Material characteristics of dental ceramic mater ials•·9•
Flexural strength [MPa)
Fracture toughness [MPa m112]
Glass-ceramics: Dicor Empress
115 182
1.93 1.77
547 292
3.55 2.48
600 1000
5.00
Glass-infiltrated ceramics: ln-Ceram Alumina ln-Ceram Spinel/ Oxide ceramics: A/703 Zr02
10.00
1.2.2 Factors that determine the strength of
dental ceramic restorations
The strength of a ceramic restoration is determined by the microstruc ture (density, number of crystals) of the dental ceramic material it is made from. The presence of initial microcracks, pores or impurities (e.g., due to processing errors) in the microstructure is a major issue. Such defects can lead to the development of cracks that can critically weaken a presumably stable material. For clinical success, the ceramic materials used for dental restora tions must meet the following requirements: High flexural strength High fracture toughness (achieved by crystalline reinforcement high crystal content, etc.) Homogeneity of the microstmcture (absence of microcracks, pores, etc.) Flawless processing (ideally, using industrially manufactured blanks). • •
=
•
•
7
Chapter 1
Scientific Aspects of Dental Ceramic Materials
1.2.3 Comparison of chemica l a n d physica l properties of metals a n d ceramics Metals and ceramics respond to stress loads differently due to differ ences in the chemical structure of the two material classes. Regarding their chemical structure, metal atoms form uniform crystal lattices by attraction through electron clouds (metal bonds). As these bonds are non-directional (i.e., they have no preferential direction), stress load ing may lead to a shifting of lattice levels without a loss of cohesion of the atoms. This mechanical property is responsible for the charac teristic elastic ductility ofmetals5• In the case of ceramic materials, metal atoms form bonds with non-metal atoms via ion bridges. Cohesion occurs due to the opposite charges of the particles. When the lattice is deformed due to stress, particles with the same charge may suddenly be shifted opposite to each other, resulting in the immediate dissolution of the bond. These interactions are responsible for another main characteristic of ceramic materials: brittleness. As a result, ceramic materials demonstrate little or no elasticity or ductility. Because they are brittle, ceramic materials are susceptible to tiny microstructural flaws (microcracks) from which macroscopic cracks may grow. Once the bonds between the atoms have been broken, they can only be rejoined by firing the material at very high temperatures. Physiologic temperatures in the mouth are too low for this. In metals, on the other hand, the same types of cracks (processing flaws, etc.) tend to "heal". Because metals are very ductile, rounding of the edges of the crack occurs, thus "de-fusing" the situation10• By virtue of their chemical structure, ceramics are very resistant to pres sure forces but, unlike metal, they have little resistance to tensile stresses. In summary, ceramics are hardly comparable to metals due to the differences in their chemical and physical properties. Due to the spe cific properties of ceramic materials, small material flaws can result in the failure of a dental ceramic restoration8.
8
1.2 Physical Properties
1.2.4 Zirconium dioxide !Zr02l Zirconium dioxide, or zirconia (Zr02), is an oxide ceramic. Compared with other ceramic materials, zirconia distinguishes itself through superior flexural strength and fracture toughness. The outstanding material properties of zirconia can be attributed to the following fac tors at the microstructural level: Zirconia is a single-phase (purely crystalline) ceramic Zirconia crystals are very small (particle size: < 0.4 �m) Zirconia crystals are uniform in shape and size (Fig4). •
•
•
In addition to being extremely stable, zirconium dioxide has another important feature: fracture toughness. The fracture toughness of zir conium dioxide is nearly twice as high as that of alumina. The high strength of zirconia is achieved through a process known as transfor mation toughening, which is based on exploitation of the phase trans formation capacity of the crystalline structure of zirconium dioxide. In this process, transfonnation of the tetragonal phase to the mono clinic phase is induced by applying concentrated stress to a crack tip, resulting in an approximately 4 percent increase in the volume of the zirconium dioxide crystals. Because of the resulting compression stress within the material, the ends of the crack are pressed together, thus preventing crack growth (Diagrams 4a and4b).
Diagram4a
Diagram4b
9
Chapter J
Scientific Aspects of Dental Ceramic Materials
1.3 Optical properties The optical properties (translucency, light transmission, etc.) of con ventional dental ceramic materials are very similar to those of dental hard tissues. For this reason, ceramics are the material of choice for dental restorations in esthetically important regions. The esthetic appearance of a ceramic material is dictated by the translucency of the material. As described in the previous section, the translucency of different ceramic materials varies. The more "stable" ceramics are more opaque during to their crystalline structure. Some are very opaque. ln-Ceram Zirconia, for example, is just as opaque as a gold alloy6. In accordance with these differences in optical qualities, the suit ability of a given ceramic material is determined by the location of the restoration, the stump shade (e.g., a discolored non-vital abutment tooth; c.f Chapter 5), and the space requirements for the restoration. The translucency of ceramic materials of defmed thicknesses can be ranked as follows1•2•6• Veneering ceramics (0.5 mm) >Empress I (0.5 mm) > In-Ceram Spinell (0.5mm) >Empress II (0.5mm) >Empress I (0.8mm) >Pro cera A1203 (0.5 mm) >Empressll (0.8mm) >Zr02 ( 1 mm) >In-Ceram Alumina (0.5 mm) > In-Ceram Zirconia (0.5 mm) (c.f Fig 5). Material thickness is a co-determinant of translucency. If a discol ored non-vital tooth is to be restored, a larger amount of space is need ed for a glass-ceramic restoration. A more opaque ceramic material (e.g., zirconia) must be used to ensure optimal preservation of tooth substance in cases in which an all-ceramic restoration is to be placed. Optical comparison of samples of differ ent ceramic materi als with equal slice thicknesses IO.Smml. From left to right: veneering ceramic !dentin mass), Empress I Zirconia, ln-Ceram Alumina, and ln Ceram Zirconia.
Fig. 5
10
References
References 1. EdelhoffD, Sorensen JA. Light transmission through bovine de ntin and all ceramic frameworks. J. Dent Res 2001 ;80:600, IADR Abstract No. 0588. 2. EdelboffD, Sorensen JA. Light transmission through all-ceramic frameworks dependent on luting material. J Dent Res 2002;81 :A-234, IADR Abstract-No. 1779. 3. EdelhoffD, Sorensen JA, Spikermann H. Light transmission through all ceramic frameworks dependent on luting material. lot J Artificial Organs 2003; 26(7):643, ESAO Abstract No. P88. 4. Filser F, Liithy H, Scharer P, Gauckler L. All ceramic dental bridges by the direct ceramic machining (DCM). Materials in Medicine Vol. I . M. Speidel & P. Uggowitzer (Eds ), Ziiricb: VDF Hoch sc bulverlag 1998: !65-189. 5. Gehre G. Keramische Werkstoffe. Ln: Eichner K, Kapper! HF. Zalmarztliche Werkstoffkunde und Verarbeitung, Vol. I . Heidelberg: Hiithig Verlag, 1996: 326-372. 6. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, Haselton DR, Stanford CM, Vargas MA. Relative translucency of six all-ceramic systems, Part J: Core materials, J Prostbet Dent 2002;88:4-9. 7. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, Haselton DR, Stanford CM, Vargas MA. Relative translucency of six all-ceramic systems, Part II: Core and veneer materials, J Prosthet Dent 2002;88: I 0-5. 8. Kappert HF. Keramik als zahniirztlicher Werkstoff. ln: Strub JR, Tiirp JC, Witkowski S, Hiirzeler MB, Kern M (Eds). Curriculum Prothetik Vol. 2.Berlin: Quintesseoz,l999:63l -660. 9. Liitby H. Strength and toughness of dental ceramics. In: CAD/CAM in Esthet ic Dentistry CEREC 10 Year Anniversary Symposium. WH Mormann (Ed.). Chicago: Quintessence, 1996:229-240. 10. Marx R. Modeme keramische Werkstoffe fiir iisthetische Restaurationen-Ver starktmg und Bruchzahigkeit Dtsch Zahniirztl Z; 1995;48:229-236. .
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Chapter 2
Processin g Methods
The starting material for any aU-ceramic dental restoration is a ceram ic powder that can be shaped into the desired form by a variety of dif ferent processing methods. The exact type of processing technique used and the method of execution (by hand or machine) depends on the type of ceramic material selected for the restoration. The development of computer-aided design and manufacturing (CAD/CAM) technolo gies for dental applications now makes it possible to fabricate ceramic restorations from densely sintered oxide ceramic materials that are dif ficult to process by hand. All-ceramic processing methods and the corTesponding types of ceramic materials can be divided into the follm.ving groups.
Manual processing
Machine processing
t Layering, pressing
Gloss-ceramics
Slip costing, gloss infiltration
Gloss-infiltrated
Copy-milling
ceramics
CAM
Oxide ceramics
CAD/CAM
2.1 Manual Processing Methods 2.1.1 Layering Layering is a processing method used to fabricate porcelain-veneered crowns and layered veneers from glass-ceramics. The starting materi als are ceramic powders supplied by the various manufacturers in a range of different shades and translucencies. In the first step, the ceramic powder is mixed with modeling fluid or distilled water to produce a slurry. The slurry is applied in layers to the substructure (framework, fireproof die). The restoration is built up in layers corresponding to the anatomical dimensions, color and translucency of the natural tooth. The applied ceramic mass is blotted frequently in order to make the piece as dense and pore-free as possi14
2.1
Manual Processing Methods
ble before sintering. The layered piece is placed in a ceramic furnace and sintered at the required temperature (approximately900°C). The powdered glass particles soften and flow together (sinter) at the parti cle inte1faces (Fig 1 and Diagram 1). � Special considerations: As the air between the particles must be able to escape during heating, sintering must be performed in a vacuum envi ronment The piece must be modeled on an enlarged scale Sintering shrinkage is extensive (up to 40%). � Drawbacks: Pore fonnation is inevitable - This results in weakening and a risk of de-lamination.
I
b
Diagrams 1 a and 1 b
I
Surface structure (a) before and !bl after sintering.
Fig 1 After layering, the vnsintered piece is roughly 40% larger than the size after sintering. The challenge for the laboratory technician is to Ioyer on the different optical features of the dental hard tissues in the rig ht places in spite of sintering shrinkage. 15
Chapter 2
Processin g Methods
2.1.2 Pressing The press technique was developed for the manufacture of ceramic inlays, onlays, veneers and crowns. The Empress® system is the pre cursor of a number of similar pressed ceramic technologies now offered by different manufacturerss. The starting material is usually a leucite (or lithium disilicate) reinforced glass-ceramic supplied in the form of industrially pre-sintered ingots. Heat-pressed ceramic restorations are made using the lost wax principle originally used in metal casting. The restoration is first modeled in wax and invested in a special muffle. The softened glass ingot is then placed in a specially designed (Empress®) press furnace and pressed at 1180°C (pressure: 5bar) into the mold created by the burned out wax (Fig 2). Ingots for pressed-ceramic restorations are available in a variety of different shades and translucencies. The materials can be processed by two different methods. First, restorations can be pressed to full contour and characterized by surface staining. Alternatively, only the frame work can be pressed and then veneered by the layering technique. --. Special considerations:
Heat-pressing produces glass-ceramic restorations of optimal quality (no pores) The restorations are scaled to the original size No shrinkage occurs.
Fig 2 16
Specially designed muffle with a pressing cylinder.
2.1
Manual Processing Methods
2.1.3 Slip Casting and Glass Infiltration The method of slip casting high-strength alumina cores for glass infil tration (In-Ceram® technology) was developed before the arrival of machining techniques for industrially pre-fabricated, porous ingots7• However, pre-fabricated ingot systems have become more popular due to their superior quality. The slip casting procedure is similar to the layering technique. Fine-grained alumina powder is mixed with modeling fluid to produce a slip, which is applied in layers to a special die to build up the sub structure. The modeled piece is subsequently sintered (for 2hours at 1120 °C). Sintering does not lead to the fusion of alumina pa1ticles, but makes them become more tightly packed. Glass infiltration of this porous substructure is, therefore, performed in the second step of the procedure; first, lanthanum powder is mixed with a special solvent and applied in excess to the external surface of the substructure (Fig 3). The piece is then fired (for 4 how·s at 1100°C) to melt the glass patiicles. The molten glass is drawn into the fine pores of the substructure (by capillary suction), yielding a high-strength, "glass-infiltrated" alumina substructure. _.
Special considerations: The use of pre-sintered blanks ensures reproducible quality Restorations are milled on a scale of 1 : I No shrinkage occurs during infiltration.
_.Drawbacks: - Suboptimal infiltration leads to reduced material strength.
Fig 3
The brown lanthanum powder is placed on a gloss plate, mixed with special fluid, and applied with a brus h The sub structure is white before infiltration. The fin ished piece must be visually inspected for infiltration quality; the improperly infiltrated piece is light brown and spotted in the m id dle, whereas the correctly infiltrated piece is dark brown with areas of excess gloss on the s u rfo ce. .
17
Chapter 2
Processin g Methods
2.2 M a c h i n i n g Machining systems use industrially manufactured ceramic blanks with improved mechanical properties to produce ceramic restorations of superior quality. The manufacturing process may be mechanical (copy-milling) or automated (CAD/CAM).
2.2.1 Copy Mill ing In copy-milling (Celay® system), a resin composite replica of the restoration is fabricated on a master cast. A scanning tool traces the replica, which serves as the exact template for precision copy-milling of the restoration from a ceramic blank1• In-Ceram blanks are most commonly used for copy-milling of dental ceramjc restorations today. �S pecial considerations: - Copy-milling involves manual fabrication and mechanical
scanning of a replica of the restoration. �Drawbacks: The range of indications is limited A relatively large amount of time is required for manual pro duction and mechanical scanning of the replica CAD/CAM techniques are increasingly replacing copy-mil ling.
18
2.2 Machining
2.2.2 Computer Aided Machining Computer-aided machining (CAM) is similar to copy-milling in that a replica of the restoration must be fabricated by the dental technician. The difference is that in computer-aided machining, the replica is scanned by optical scanning technology (laser, white-light scanner) and digitized. The digitized data are then used for precision machining of the restoration from an industrially manufactured blank. Pre-sintered zirconia blanks (e.g., Cercon) are most commonly used for computer-aided machining of ceramic dental restorations today. As they are subject to approximately 22% shrinkage during sin tering, the data set used for milling must be adjusted to compensate for sintering shrinkage. Special software packages are available for this purpose2. __..Special co nsiderations: Range of indications for the procedure Manual fabrication process Optical scanning of a replica of the restoration. The CAM data set must be adjusted to compensate for sinte ring shrinkage (shrinkage factor). __..Drawbacks: A relatively large amount of time is needed for fabrication of the replica CAD/CAM techniques are increasingly replacing computer aided machining.
19
Chapter 2
Processing Methods
2.2.3 Computer Aided Design/Computer Aided Man ufactu ring The Cerec® system was the forerunner in the field of CAD and manu facturing of dental ceramic restorations6. The availability of more sta ble oxide ceramics (alumina, zirconia) has greatly increased the pop ularity of CAD/CAM technology. Improvements in the software now make it possible to process pre-sintered ("green") or white-stage zir conia blocks. This effectively expanded the range of applications for CAD/CAM technology, and all-ceramic bridges can now be manufac tured by this technique. CAD/CAM systems are mainly used to manufacture restorations from densely sintered (pre-sintered) ceramic blocks of virtually all types, but a number of other materials (titanium, synthetic mate1ials) can also be processed. If unsintered ("green") zirconia blocks are used, the blocks are first be mjlled and subsequently sintered to full density in the sintering furnace that comes with the system. Three basic steps are involved in the manufactming process with all CAD/CAM systems: Data acquisition (optical and mechanical), CAD, and CAM of the restoration. Due to the extremely high cost of CAD/CAM systems, a current trend in this field is the development of specialized CAD/CAM cen ters. With this set-up, the individual dental laboratory only needs to purchase the system's scanning unit. The scanned restoration data are transferred electronically to a CAD/CAM center. Within a few days, the laboratory receives the manufactured coping that is ready for veneering. The Procera® system marketed by Nobel Biocare (Sweden) utilizes this kind of central processing set-up.
20
References
__.Special considerations: Pre-sintered ceramic blocks come in a wide range of materials CAD/CAM systems that use presintered ("green") or white stage zirconia blocks are a new development The die is scanned optically. __.
Drawbacks: Requires highly specialized equipment High investment costs lndustly-dependent (continual R&D-related changes).
References 1. Eidenbenz S, Scharer P. Das Kopierschleifen keramischer Formkorper. Phillip J 1994;11:91-95. 2. Filser F, Liithy H, Gauckler L, Scharer P. AU-ceramic restorations by new direct ceramic processing (DCM). J Dent Res I998;77(Special1ssue):762. 3. Gehre G. Keramische Werkstoffe. ln: Eicbner K, Kapper! HF: Zabnarztliche Werkstof'f1.'11nde und Verarbeitung, Vol. l . Heidelberg: Hiithig Verlag,l996: 326-372. 4. Kapper! HF. Keramik als zahnarztlicher Werkstoff. Tn: Strub JR, TUrp JC, Witkowski S, Hiirzeler MB, Kern M (Eds.): Curriculum Prothetik, Vol. 2. Berlin: Quintessenz, 1999:631-660. 5. Marx R. Moderne keramische Werkstoffe fur iisthetiscbe Restaurationen-Ver starkung und Bruchzabigkeit. Dtsch Zahnarztl Z 1993;48:229-236. 6. Mormann W, Krejci I. Computer designed inlays after 5 years in sint: Clinical performance and scanning electron microscopic evaluation. Quintessence lor 1992;23: I 09- 1 1 5 . 7. Sadoun M. All-ceramic bridges with slip-casting technique. 7th lnt. Sympo sium on Ceramics; Paris, Sept. 1988. 8. Wohlwend A, Scharer P. Die Empress-Tecbnik; Eiue neue Moglichkeit Einzelkronen, Inlays und Verblendschalen berzustellen. Quintessenz Zahntech 1990; 1 6:966-978. 21
(Y) '-
,p> •
a_ 0
-t:
u
23
Chapter 3
Veneers
3.1 •
•
•
Ind ications
Teeth resistant to bleaching - Tetracycline staining - Inadequate response to bleaching (internal or external). Morphological anomalies Generalized malformations and deformities Conoid teeth Diastema closure Closure of interdental triangles Tooth reshaping (augmentation oflength, size). Tooth reconstruction Crown fractures Loss of tooth structure due to abrasion Loss of tooth structure due to erosion.
3.2 Co ntraindications • • • •
24
Very darkly stained teeth Insufficient enamel available Large approximal fillings Bruxism.
3.3 Clinical Guidelines
3.3 C l i n i c a l G u ideli nes •
•
• •
The preparation margin should preferably be maintained within the enamel whenever possible. In patients with larger areas of dentin located at the inner surface of the preparation, the margin must always be located entirely within the enamel. Sufficient space available for a stable laminate. Preparation guidelines: Cervical/buccal � 0.5 mm Cervical/approximal >0.5 mm Incisal/buccal >0.7 mm lncisal > 1 to 1.5 mm Palatal finish line: slightly concave butt margin.
- 0.5 mm 1'-t "1 ·> 0.5 m m H
> 0.7mm ,......
___..'f'_.
.... _._ .. ..... ___. ..... ... --. .
.___..._._ ...
..
> l.5 mm
Diagram 1
Schematic diag ra m of tooth preparation.
25
Chapter 3
Veneers
3.4 Step-by-step : C l i n i c a l Proced u re for t h e Fa brication of Veneers Case presentation
The patient's chief complaints were perceived shortness of teeth 11, 21 and 22 and diastema. Slight palatal displace ment of tooth 22 was additionally present.
Figs 1 to 3
26
3.4
Step by step Clinical Procedure for the Fabrication of Veneers -
-
:
Diagnostic procedure
The desired restoration was modeled 1n wax.
Fig 4
A silicone impression of the additive wax-up was then taken.
Fig 5
•
Self-curing resin composite loaded on the silicone index.
Fig 6
An acrylic mock-up derived from the diagnostic wax-up is used to try out the desired restoration in vivo.
Figs 7 and 8
27
Chapter 3
Veneers
Tooth preparation aids Additional silicone keys made from the wax-up serve as references for tooth preparation.
Fig 9
A horizontally sectioned silicone index is used to gouge preparation depth.
Fig 10
A mesiodistolly sectioned si licone index is used to gouge preparation length.
Tooth preparation
Fig 1 1
Axial reduction I: interdental separa tion !separating diomondl.
Fig 1 2
A thin, dark retraction cord is placed bucolly to better visualize and pro tect the gingival margin .
Fig 13
Axial reduction II: fa cial grooves. Two to three facial grooves ore created in the facial surface of the teeth using a nor row, rounded, conical diamond bur. The depth of each groove 10.5 m m I is checked using the silicone index. 28
3.4
Step-by-step: Clinical Procedure for the Fabrication of Veneers
Axial reduction Ill: gross prepara tion. Buccal and interdental reduction is completed to yield the desired tooth shape. Both the shoulder and the approximal mar gins should be at least 0.5 mm in width Ia large, rounded parallel diamond bur should be used to keep the surface from becoming wavyl.
Fig 14
At least 1 to 1.5 mm of incisal clear ance is required. An approximately 0.5 mm deep palatal finish line is made using a round diamond bur in order to optically conceal the incisal edge.
Fig 15
The silicone keys are used to continuously gouge the results of tooth preparation.
Figs 16 to 18.
29
Chapter 3
Veneers
All sharp edges are rounded off with a flexible disk, and fine preparation is completed.
Fig 19
Figs 20 and 21
Final view of the preparations.
lmpressioning
Figs 22
and 23 A second, thicker deflection cord ls placed in the sulcus 5 to 10 minutes before taking the impression.
30
3.4
Step-by-step: Clinical Procedure for the Fabrication of Veneers
Provisionalization indirect mock-up (acrylic resin shells) made by the laboratory can be used to provide highly esthetic temporaries for demanding patients. In other cases, a direct mock-up made from the silicone index is nor mally sufficient for temporization. An
a. Indirect provisionals (acrylic resin shells)
Indirect provisionols !acrylic resin shells! mode by the dental laboratory. For better retention, provisional restorations should always be fused into a single piece.
Figs 24 and 25
The ac ry lic resin shells ore relined with polymethyl methocrylote and luted to the teeth.
Fig 26
Esthetic and functional check of the seated provisional restoration.
Fig 27
31
Chapter 3
Veneers
b. Direct provisionals
Self-curing resin is loaded onto the silicone index, pressed over the prepared teeth, and allowed to cure in place on the teeth.
Fig 28
Finished monochromatic provision cis prepared by the direct technique.
Fig 29
Temporary cementation
The prepared teeth ore spot etched with 30% phosphoric acid and then coated with unfilled resin. The provisionals ore then seated and light cured.
Figs 30 to 32
View of the temporarily cemented acrylic resin shells.
Fig 33
32
3.4 Step-by-step: Clinical Procedure for the Fabrication of Veneers
Wax try-in
Wax shells made according to the first additional wax-up ore tried on in order to refine the diagnosis.
Fig 34
Biscuit bake try-in
Figs 35 and 36
The laminates are applied to the prepared teeth with glycerin gel.
Delivery appointment
Figs 37 and 38
View of the finished veneers prior to cementation. 33
Chapter 3
Veneers
Prepa ring the teeth for final cementation
After the temporaries have been removed, the prepared teeth are cleaned as follows: first, scalers are used to remove any remaining resin from the prepared teeth, and all bonding surfaces are thoroughly cleaned with non-fluoride paste. The preparations are then isolated with rubber dam and the interdental spaces are separated using wedges and a matrix. If there is no more than 10 to 20 percent dentin exposure at the inner surface, the preparations are simply etched with 35% phosphor ic acid before applying one coat of bonding adhesive (Fig 39). The internal surfaces of the veneers are etched with 10% hydroflu oric acid for 90seconds and then thoroughly rinsed with water and degreased with medicinal alcohol. After degreasing, two to three cycles of silanization and drying are perfonned (Fig 40 and41). Finally, a light coat of adhesive resin is applied to the bonding surface of the veneer.
Fig39
Fig40
Fig 41 34
Silanization of an
etched veneer.
3.4
Step-by-step: Clinical Procedure for the Fabrication of Veneers
Cementation A fine-hybrid resin composite heated to 50 °C is normally used for cementation of porcelain veneers. Light-curing proceeds from the palatal surface to the buccal surface of tbe veneer. Each surface is cured with intermittent light for I minute in order to protect the pulp from overheating. Excess resin is removed using foam pellets when the resin is still soft, or with scalers, rotating and oscillating instruments and strips after tbe resin has hardened (Fig42).
Fig42
Reca l l
Fig s 43 to 45
Views at recall, 1 week after placement of the restorations. 35
Tbe authors are grateful to the patticipating dental technicians for the excellent restorations they provided and for their consistently gooo teamwork. We would especially like to thank Walter Gebhard (Geb
hard AG, Zurich), Bertrand Thievent (Benrand Thievent AG, Dental Laboratory, Zurich), Arnold Wohlwend (Wohlwend Innovative Dental
Technik. Zurich), and KBTM Intern Dental Laboratory (Director: Ana
Suter). Special thanks also to Heinz Liithy for his contributions regard ing the technical aspects ofdental ceramic materials.
Title orthe original German edition: Oenlalc Keramiken Aktuelle Scll\\�q)unkte fur die Klinik ¢} 2008 by Christoph Hamm
Quinte=�ee British Library Cataloguing in Publkntion Data Dental ceramics : essential factS for cosmetic dentists I. Derlla) •.x:nunks t. Hanuncrk. Christoph
6t7.6'95
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ISBN: 9781850971 818 0 2008 b y Christoph Hamm<'flc
Quunessenre l�•blisb.ingCo. ltd.
G1aftou Road. New Maldcr�. Surrey K'l1 JAil Great Britain www.quinlpub.oo.uk All rights 1\..">Scrvcd. This lx>Ok or any pan there ofmay not be reproduced, stored in a retrreval f>)'Slem. or lransmined io aoy fonn or by an y means. electronic. mechanical. piK)tocopying. or otbCn\'iSC. without priorwriuen pcm1i.ssion ofthepublisher. Editing: Quimessence Publishing Co. Ltd, London Translation: Suzyon O'Ne3l Wandrey,Derlin layoutand pmduction: Quinlcss:.:n7. \'ertags-GmbH, &"flin Printing aud buJding: Al Druck und Darentecbnik GmbH. Kernpten Printed in Gennany IV
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37
Chapter 4
All-ceramic Single Crowns
4.1
Ind ications
When planning all-ceramic single crown restorations, the choice of ceramic restoration system is determined by the following factors: Stump shade Space requirements/clearance (tooth reduction) Translucency of adjacent teeth Strength requirements (anterior or posterior region). • •
• •
The ceramic materials available today allow the dental laboratory technician to select an appropriate ceramic restoration system for each individual situation - at least from a materials viewpoint. Based on their material strength and optical properties, the follow ing ceramic materials can be used in anterior and/or posterior applica tions as desc1ibed in Table 1. Table 1
Gloss-ceramic
Dark stump shade
Shoulder preparation
Adjacent tooth translucency
Region
No
0.8 to 1 mm
High
Anterio r
1 to 1.2mm
Moderate, high
Anterior, posterior
No/Y es
Moderate, low
Anterior, posterior
Gloss-infiltrated No/Yes ceramic Oxide . cerom1cs
No/Yes
If an oxide ceramic core is to be placed on a very transparent tooth, more space is required for the restoration compared with other ceramic core materials, such as glass-ceramic. The tooth reduction design must be modified accordingly. Space is required for: The core (roughly 0.5 mm) The opaque layer The veneering ceramic (> 1 mm). • •
•
New and improved standard colors of ceramic core and veneering materials now make it possible to reduce the layer thickness in accor dance with the modem standards of tooth structure preservation. 38
4.2 Tooth Preparation
4.2 Tooth Prep a ration Familiarity with specific all-ceramic tooth preparation guidelines is cru cial for the clinical success of all-ceramic restorations. Apart from the usual biologic requirements (healthy pe1iodontium, etc.), which are the same for all types of restorations, specific technical requirements apply to all-ceramic crown restorations. Inadequate tooth preparation (e.g., sharp edges or inadequate space for the restoration) was responsible for the dis appointing initial clinical survival rates for all-ceramic crowns'6. Due to the increasing use of computer-aided design and manufactur ing (CAD/CAM) teclmology for fabrication of dental restorations, additional technical factors must also be considered. CAD/CAM sys tems generally utilize optical scanning technologies that specifY mini mum taper and undercutfree preparation of the abutment tooth. Tooth preparati on guidelines for aJI-ceramic crowns: Circular shoulder with rounded inner edges or chamfer (Fig 1). Reduction requirements: Glass-ceramic systems: Shoulder 0.8 to 1 mm Axial 1.0 to 1 .5mm Incisal 1.5 to 2mm Occlusal 1.5 mm minimum. Reinforced ceramic core systems: Shoulder l to 1.2mm (NB: radius) Axial 1.2 to 1.5 mm 1.5 to 2.5 mm (NB: radius) Incisal Occlusal 1.5 mm minimum Uniform layer thickness Minimum 6 degree stump taper No sharp angles or edges.
• •
•
• •
If the shoulder angle is > 90 degrees, chamfer preparation is not recom mended for all-ceramic restorations as this would increase the risk of ceramic fracture27• In order to meet the modem technical requirements without making major changes in routine clinical practice, a modified version of the original St. Moritz prep set (Intensiv SA, Gracia, Switzerland) of 1995 was modified for ceramic crown and laminate applications (Fig 1 ). 39
Chapter 4
All-ceramic Single Crowns
.-
Modified St. Moritzer Crown and Laminate Prep Set (lntensiv SA, Granda, Switzerland} of 2006. Some of the original instruments were modified or replaced to comply with the modern requirements for all-ceramic restorations. Burs !left-right!: Veneer diamond (newl, separating diamond, shoulder diamond, shoulder finishing diamond (now wider!, football diamond (now rounded, football finishing diamond, diamond finishing bur with 3-degree taper (new, for CAD/CAMJ.
Fig 1
Diagram 1
\\
4.3 Cl inical S u rvival Thanks to the technological advances in dental ceramic materials, it is now possible to find a ceramic solution for nearly every clinical prob lem. It is conceivable that all-ceramic crowns could replace metal ceramic crowns in the future if they perform well in clinical practice over the long-term. The survival and complication rates of all-ceramic and metal ceramic crowns were compared in a recent review of the literature published in English and German from 1990 to 200419• Relevant clin ical trials with a minimum observation period of at least 3 years were included. The twenty-three studies on all-ceramic crowns that the authors located are listed in Tables 2 to 4 according to material type and sys tem. The annual failure rate for glass-ceramic crowns was 2.1 % for a total of 1581 anterior and posterior restorations.
40
4.3
Clinical Surviva l
Reinforcement of ceramic materials resulted in an improvement of clin ical survival: The annual failure rate for the anterior and posterior restorations studied decreased to 0.8 % and 0.6 % for glass-infiltrated ceramic ( 1269 crowns) and densely sintered alumina ceramic (168 crowns), respectively. The annual failure rate for porcelain-fused-to-metal (PFM) crowns was higher (2.9 %). This was determined by a single study that met the inclusion criteria 13. The results of this study show that ceramic core-reinforced crowns placed in the anterior and posterior region have a high rate of success. The clinical success rate for "weaker" glass-ceramic crowns was some what lower than that for high-strength crowns, but comparable to that for PFM crowns. The use of zirconia cores should lead to further improvement of the clinical success rate, but long-term studies are not yet available. The decision-making process regarding the selection of ceramic materials for dental restorations is described in the flow chart below (Decision flow chart 1).
High esthetic demands
· Quality of the abutment tooth o r core
..---� -
I
Tooth-colored abutment tooth or core; adhesive cementation is possible
I I
-
\
Discolored abutment tooth or core; adhesive cementation is not possible
-� locations. subjected to high masticatory forces
All-ceramic, (metal-ceramic) Decision flow chart 1
for the selection
Zirconia, Alumina, (metal-ceramic) of dental ceramic materials.
41
Chapter 4
Table 2
All-ceramic Single Crowns
Survival rates for all-ceramic crowns
Author, year
Crown materials (system)
Indications Observation period
Failure rote Overall Annual
Bindl et o l 2004"2
Feldspot
Anterior
3.7 years
5.6%
1.5%
Estafon et ol 19997
Feldspot,Gioss-
?
4 years
0.0 %
0.0 %
Erpenstein et ol 2000<>
ceramic !Dicorl
7 years
24.3 %
3.5 %
Posterior
4 years
24.8 %
6.5 %
Glass-cero m ic
Anterior,
4.3 years
16.6 %
3.9 %
I Dicorl
Posterior
Sjorgen et al 19992j
Glass-cera mic
Anterior,
18.0 o/o
!Dicorl
Posterior
6.1 years
2.95 %
Edelhoff et al 20005
Glass-cero m ic
Anterior,
I Empress)
Posterior
Glass-ceramic
Anterior,
I Empress)
Posterior
Sjorgen et al 1998'24
Gloss-ceramic
Anterior,
I Empress)
Posterior
Sorensen et o l 199825
Glass-ceramic
Anterior,
!Empress)
Posterior
Glass-cera mic
Anterior,
I Empress]
Posterior
Gloss-ceramic
Anterior,
I Hi-Cerom"'l
Posterior
Kelsey et a l 1995
1x
Fradeani et al 20028
Studer et al 199826
Hankinson et ol
�
Cheung 19914
42
1
Anterior,
IDicorl
Posterior
Glass-ceramic I Dicorl
Meier et al 1992'5
Bieniek 199221
Gloss-ceramic
10 Glass-ceramic 994
Anterior,
IOptec HSPJ
Posterior
Glass-ceramic
Anterior
!jacket crowns)
4 years 1 1 years
2.0% 4.8 o/o
0.5 % 0.4 %
3.6 years
6.7%
1.9 %
3 years
1.3 %
0.4 %
5.1 years
8.7 %
1.7 %
5 years
4.3 %
0.9 %
5 years
6.3 %
1.3 %
3.3 years
26.5 %
=
8.00 %
=
:::
-
=
4.3
Table 3
Clinical Survival
Survival rates for all-ceramic crowns: gloss-infiltrated ceramic
Author, year
Crown materials (system)
Indications Observation period
Huls 1995"
ln-Cerom
Anterior,
Alumino
Posterior
Mclaren et al. 200014 ln-Ceram Probster 199710 Scotti et ol. 199521 Segal 200122 Bindl et ol. 20023
Anterior,
Alumina
Posterior
ln-Cerom
Anterior,
Alumino
Posterior
ln-Ceram
Anterior,
Alumina
Posterior
ln-Ceram
Anterior,
Alumino
Posterior
ln-Ceram
Posterior
Failure rate Overall Annual
3 years
2.7%
0.9%
3 years
4.0 %
1.3 %
6 years
36.5 %
6.1 %
3.1 years
1.6 o/o
0.5 %
6 years
0.9 %
0.2%
3.2 years
7.0%
2.2%
Alumina, Spinel( Fradeani et ol. 20029 ln-Ceram
Posterior
4.2 years
2.5 %
Spinel I
Table 4
0.6 o/o
� '::
=
Survival rates for all-ceramic crowns: oxide ceramic
Author, year
Crown materials (system)
Indications Observation period
Failure rate Overall Annual
Oden et al 199817
Alumino Alz03
Anterior,
5 years
3.1 %
IProcerol
Posterior
0.6 o/o
10 years
6.5%
0.7 %
Odmann et al 200118 Alumino Al203 IProcerol
Anterior, Posterior
43
Chapter 4
All-ceramic Single Crowns
4.4 Clinical and Laboratory Proced u res Dentist Initial consu ltation Good communication between the patient, dentist and dental techni cian is crucial for the selection of optimal restorative materials. The procedures for the dentist and the dental laboratory are described step by-step in the clinical case study presented below.
Figs 2a to 2c
This young woman had been dissatisfied with the appearance of her anteri or teeth for several years. The uneven incisal plane, that is, tilting of the central incisors towards midline !"teeth too short") and the different colors of her old composite fillings bothered her. The plastic-faced crown at non-vital abutment tooth 12 become discolored over the course of the years and was perceived as unsightly. The esthetic problems were readily visible due to the patient's high smile line. In addition to the tooth discoloration problems, there was also noticeable gray discoloration of the marginal gingiva at tooth 12. The patient wished to have metal-free dental restorations. Photographs displaying the lips at rest, slightly parted, and in full smile are crucial for treat ment planning and communication purposes. 44
4.4
Clinical and Laboratory Procedures
Figs 3a to 3d
The preliminary diagnostic work begins during the initial consultation. Composite filling material is used to simu late length and shape corrections for demonstration purposes. The patient and the dentist con then mutually evaluate and discuss the feasibility and limitations of the patient's expectations. An alginate impres sion of the simulated situation is subse quently mode in order to communicate the desired goals to the dental technician. In this specific case, the dentist additionally explained to the patient that, because the gray discoloration of her gingiva is caused by discoloration of the tooth root, little or no improvement con be expected, even if on a ll-ceramic restoration is used.
45
Chapter 4
All-ceramic Single Crowns
Lab Diagnostic work-up The success ofa prosthetic restoration depends on a number of factors, including accurate reproduction of the natural tooth color. The shape and anatomical position of the teeth and their direct interactions in the dentofacial complex also play a major role. The dental technician must reconcile the esthetic expectations of the patient and dentist with the technical limitations of the materials and the patient's financial con straints. The following records are needed for diagnostic planning: Description of the esthetic expectations of the patient Articulated study model (Fig 4b) Pretreatment photographs (Fig4a): Portrait photograph View of lips at rest View of lips slightly patted View of full smile. •
•
•
Fig4a
Fig 4b 46
Initial study model.
4.4
Clinical and Laboratory Procedures
Step-by-step procedure Using the study model submitted by the clinician, the dental technician (DT) makes an additive wax-up with corrections for tooth position or angulation. Two silicone indexes are made from the wax-up; one is used as a reference for tooth preparation, and the other for fabrication of the indirect provisionals (actylic resin shells). For patients with high esthetic demands, it is advisable to do a mock-up of one or two different restoration proposals for the patient to "try on" the proposed restorations for the team (patient, dentist and dental technician) to evaluate and discuss.
•
Mock-up of the planned restora tion.
Fig 4c
Fig 4d The thin shells are placed on the teeth to assess for proper length and phonet ics. 47
Chapter 4 All-ceramic Single Crowns
Dentist Clinical diagnosis
5o to5c A
Figs mock-up of the chosen restorative alternative is made so that the patients can try out the new look i n their mouth for a few days. This intermediate diagnostic step is advisable, especially when major changes have been proposed. It helps to achieve a precise definition of the prosthodontic goal before the start of treatment Treatment planning: • •
Tooth 12: crown Teeth 11/21 : veneers.
Fig 6 Once a precise definition of the treat
ment goals had been obtained, periodon tal/conservative treatment was performed and the old restorations were removed. Endodontic treatment was sufficient for abut ment 12; the apex was normal, but severely discolored treddishl. Based on the clinical situation !residual dentin, build-upl, internal bleaching was not performed because the patient did not wish to have the whitening procedure. A white opaquing composite was, therefore, used to mask the buccal aspect of the discolored abutment tooth.
48
Clinical and Laboratory Procedures
4.4
Lab Diagnostic wax-up and shell provisional It is advisable to place a buccal wax shield on the wax-up before start ing the provisional. This allows more space for easier intraoral posi tioning of the relined provisional. Silicone indexes of the diagnostic wax-up are also made as a reference for tooth preparation.
Fig 7a
Wax shield.
Fig 7b
Fig �c
<;ontrolled trim �! ng of plaster for
Fig 7d
fabncotton of the provtstonals.
Additive diagnostic wax-up.
Finished provisional restoration mode of pmmo resin.
49
Chapter 4 All ceramic Single Crowns -
Dentist Tooth preparation and shell provisional Diagnostic mock-ups help patients gauge their satisfaction with a pro posed restoration during the diagnostic planning stage, and changes in the planned tooth shape or position can still be made if determined necessary by the team (patient, dentist and technician). A polyether or silicone impression of the definitively prepared abutment tooth is taken at a later appointment.
Figs 7e
and 7f A silicone index of the diagnostic wax-up is made prior to tooth prepara tion. The silicone index allows for selective creation of clearance for the restoration with maximum conservation of tooth structure.
Figs Sa and 8b
The buccal and incisal aspects of the preparatio ns are assessed using the silicone index. The teeth are uniformly reduced to ensure uniform clearance for the ceramic restoration. All edges and junctions must be carefully rounded.
The diagnostic mock-up made from the diagnostic wax-up is now relined and seated as the provisional restoration.
Figs 9a and 9b
50
4.4
Clinical and Laboratory Procedures
Lab Treatment wax-up The treatment wax-up serves a number of functions. When an easily processed material is used, adjustments can be made for tooth shape and contour (Figure 1 Oa). Since the silicone index from the wax-up shows exactly how much space is available for the restoration, there are no unpleasant surprises during the ceramic layering stage. The intraorally seated treatment wax-up can influence the selection of restorative materials.
The tooth contour is determined by the external margins of the teeth, and the optical shape of the teeth by the axial ridges.
Fig lOa
b Figs lOb and lOc.
51
Chapter 4
All-ceramic Single Crowns
Dentist Wax try-in
Try-in of the treatment wax-up, which was prepared by the dental techni cian on the master cast according to the preliminary diagnostic work.
Figs lOd and 1 Oe
Lab Shade selection
Fig 1 1 a
Shade analyses should be per formed at on optimal light temperature 15500°Kl, especially when on anterior restoration is to be made. The late morning or late afternoon is an ideal time of day for shade analysis. Room light quality test cards are also helpful.
Determination of the stump shade is also required for fabrication of all-ceram ic restorations.
Fig 1 1 b
1 1 c It is very helpful to perform the shade analysis with the coping [made of alumina, zirconia, etc.l in place and to stain the cop ing intraorally as needed.
Fig
52
4.4
Clinical and Laboratory Procedures
Shade selection aids
a� ..., .u. ..,.........,.��. ��� �--
'"' ...:= "t
"''��
d Fig 1 1 d Shade guides ore useful tools for basic color determinations and simple shade analyses.
e
Fig 1 1 e Cheek retractors reduce surrounding color I red of the lips), which con interfere with the shade determination.
g Fig 1 1 f Original shade guides sup plied by o ceramics manufacturer.
Fig 1 1 g Custom shade guide.
Checklist for shade analysis • • •
Sit or stand at eye level with the patient Use indirect sunlight or daylight illumination Note colors in the surroundings and their effects: Lipstick, make-up Lurid clothing The teeth should be thoroughly cleaned beforehand Impressions should be taken beforehand. 53
Chapter 4
All-ceramic Single Crowns • • • • • • •
Disposable gloves Color rings, etc Color markers Color cards Cheek retractors Mouth mirror Camera.
Selection of ceramic materials
Factors that determine the choice of ceramic materials used for the restoration are: region, stump shade, space requirements, and bite sit uation. Region: anterior All-ceramic restorations (with or without ceramic cores) are preferable in the anterior region because of the light transmission properties of ceramic materials. Stump shade: If the abutment tooth is severely discolored (A4, > B4) the amount of color variation possible with all-ceramic restorations is greatly limited. Space requirements: If a core-reinforced (alumina, zirconia) all-ceramic restoration is to be placed, a minimum core thickness of 0.4 mm should be observed. Othetwise, there is a high risk of ceramic fracture. Bite situation: Conventional porcelain-fused-to-metal crowns should be used in patients with extreme bite problems. •
•
•
•
Biscuit bake try-in and completion of the restoration
Going from the biscuit bake try-in to the completed restoration by a diagnostic wax-up and a treatment wax-up has proved to be a success ful concept in patients with high esthetic demands.
54
4.4
Clinical and Laboratory Procedures
c
Figs 12a to 12f The silicone index from the wax-up is a useful tool for the layering design. Stump shade determination is cru cial for all-ceramic restorations because it makes it easier to predict the final result.
Dentist Biscuit bake try-in
Fig 13 Biscuit bake try-in of veneers and zirconia crown at the dental office. 55
Chapter 4
All-ceramic Single Crowns
Completed restoration
Completed restorations: zirconia crown for tooth 12, veneer !360degrees) for tooth 11, and veneer for tooth 21 !modified prepo rotionl
Figs 14o ond 14b
.
The positioning key !e.g., Pattern Resin, GC, USAl fabricated by the dental technician makes it possible to check for correct !esthetic) position of the restoration during cementation. However, it is absolutely essential to use on explorer to check margin position. The bonding procedure for different 1ypes of ceramic materials is described step by step in Chopter8.
Fig 14c
-
Frontal view and smile after placement of the restorations. The use of ceramic materials with different optical and mechanical properties compensat ed for stump shade deviations and irregularities in tooth red u ction.
Figs 15o ond 15b
56
References
References I . Bieniek KW. Vollkeramische Kronenrestaurationen aus Hi-Ceram eiue 5-
2.
3. 4. 5.
6.
7.
8.
9.
10.
11. 12.
13. I 4. I 5.
16. 17. 18.
1ahres-Studie. Dtsch Zahnarztl Z 1992;47:614-616. Bind! A, Mormann WH. Survival rate of mono-ceramic and ceramic-core CAD/CAM-generated anterior crowns over 2-5 years. Eur 1 Oral Sci 2004: 1 12(2): 197-204. Bind! A, Mormann WH. An up to 5-year clinical evaluation of posterior 1n Ceram CAD/CAM core crowns. 1nt J Prosthodont 2002;15(5):451-456. Cheung GS. A preliminary investigation into the longevity and causes of fail ure of single unit extracoronal restorations. J Dent 1991; 19(3): 160-163. Edelhoff D, Horstkemper T, Richter EJ, Spiekennann H, Yildirim M. Adhiisiv und konventionell befestigte Empress 1-Kronen. Dtsch Zahnarztl Z 2000;55:326-330. Erpenstein H, Borchard R, Kerschbalun T. Long-term clinical results of gal vano-ceramic and glass-ceramic individual crowns. 1 Prosthet Dent 2000;83(5):530-534. Estafan D, David A, David S, Calamia J. A new approach to restorative den tistry: Fabricating ceramic restorations using CEREC CAD/CAM. Compend Contin Educ Dent 1999;20(6):555-60. Fradeani M, Redemagni M. An l I -year clinical evaluation of leucite-rein forced glass-ceramic crowns: A retrospective study. Quintessence lnt 2002;33(7):503-510. Fradeani M, Aquilano A, Corrado M. Clinical experience witll Tn-Ceram Spinel! crowns: 5-year follow-up. lnt J Periodontics Restorative Dent 2002;22(6):525-533. Hankinson JA, Cappetta EG. Five years' clinical experience with a leucite reinforced porcelain crown system. Int 1 Periodontics Restorative Dent 1994; 14(2): 138-153. Hiils A. Zum Stand der klinischen Bewiihrung inliltrationskeramischer Verblendkronen. Dtsch Zahnarztl Z 1995;50:674-676. Kelsey WP 3rd, Cave! T, Blankenau R1, Barkmeier WW, Wilwerding TM, Latta MA. 4-year clinical study of castable ceramic crowns. Am J Dent 1995;8(5):259-262. Kerschbaum Th, Paszyna Ch,Klapp S, Meyer G. Verweilzeit- und Risikofak torenanalyse von festsitzendem Zahnersatz. Dtsch Zahniirztl Z 1991 ;46:20-24. Mclaren EA, White SN. Survival ofin-Ceram Crowns in a Private Practice. A prospective clinical trial. 1 Prosthet Dent 2000;83:216-222. Meier M, Richter EJ, Kupper H. Spiekennann H. Klinische Befunde bei Kro nen aus Dicor-Giaskeramik. Dtsch Zahnarztl Z 1992;47:610-614. Nuttal EB. Factors influencing success of porcelain jacket restorations. J Pros thet Dent 1961;11 :743-748. Oden A, Andersson M, Krystek-Ondracek 1, Magnusson D. Five-year clinical evaluation of ProceraAl!Ceram crowns. J Prosthet Dent 1998;80(4):450-456. Odmann P, Andersson B. Procera Ali-Ceram crowns followed for 5 to I 0.5 years: A prospective clinical study. tnt J Prosthodont 2001;14:504-509.
57
Chapter 4
All-ceramic Single Crowns 19. Pjetursson BE, Sailer I, Zwahlen M, 1-Himmerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal-ceramic restora tions after an observation period of at least 3 years. Part I: Single crowns. Clin Oral Imp! Res 2007;1 8(Suppl.3):73-85. 20. Probster L. Klinische Langzeiterfahrungen mit vollkeramischen Kronen aus In-Ceram. Quintessenz 1997;48:1639-1646 . 2 1 . Scotti R, Catapano S, D'Elia A. A clinical evaluation of ln-Ceram crowns. h1t J Prostbodont 1995;8(4):320-323. 22. Segal BS. Retrospective assessment of546 all-ceramic anterior and posterior crowns in a general practice. J Prosthet Dent 2001 ;85(6):544-550. 23. Sjogren G, Lantto R, Tillberg A. Clinical evaluation of all-ceramic crowns (Dicor) in general practice. J Prosthet Dent 1999;8 1(3):277-284. 24. Sjogren G, Lantto R, Granberg A, Sundstrom BO, Tillberg A. Clinical exami nation of leucite-reinforced glass-ceramic crowns (Empress) in general prac tice: A retrospective study. Int J Prosthodont 1999;12(2):122-128. 25. Sorensen JA, Choi C, Fanuscu MI, Mito WT. IPS Empress crown system: Three-year clinical trial results. J CalifDent Assoc. 1998;26(2): 130-136. 26. Studer S, Lehner C, Brodbeck U, Scharer P. Six-year results of leucite-rein forced glass-ceramic crowns. Acta Medicinae Dentium Helvetica 1998;3:2 1 8-224. 27. Weaver JD, Johnson GH, Bales DJ. Marginal adaptation of castable ceramic crowns. J Prosthet Dent 1991 ;66:747-753.
58
•I•
c: (])
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::l ....0
-<(
.R
. ...
1.() '
(]) •I 0.. 0 a
> I
c: 0
z
-c:
u
59
Chapter 5
Non-vital Abutment Teeth
A number of additional factors must be considered when planning the prosthetic rehabilitation of non-vital teeth. Apart from endodontic pretreatment and biomechanical factors dictating material selection and tooth preparation, esthetic factors are also crucial to treatment success. The chances of successful restoration of endodontically treated teeth reportedly range from 70 to 95 percent, depending on how the criteria of success are defined18• Leakage of bacteria into the obturat ed root canal leads to recontamination of the root canal lumen. Bacte rial microleakage and subsequent periapical re-infection as well as secondary caries and subsequent loss of retention of the restoration are major causes of endodontic failure. Microleakage occurrence is dependent on various factors including: The type of root canal filling material/cement used and the ade quacy of filling The type and quality of the provisional restoration The type and quality of the definitive restoration.
•
•
•
No cement to date has been able to achieve totally complete sealing, but different types of cement achieve significantly different levels of sealing quality. Zinc phosphate cement, for example, proved to be sig nificantly inferior to glass ionomer cement and composite cement in independent studies'(see also Chapter8.2).
5.1 Biomecha nics of Non-vital Teeth The more tootl1 structure lost through decay or removed to create an access for endodontic treatment or to prepare the teeth for restorations, the greater the extent of deformation of the remaining tooth structure during functional activity. Post placement requires the additional removal of dentin, thus further weakening the tooth. The use of a post does not strengthen the tooth prior to prosthetic restoration, but rather, it merely serves to enhance the retention of the crown and core and to transmit the forces placed on them to the remaining tooth structure. From a biomechanical point of view, the tooth, post and core comprise 60
5.2
Posts
an inhomogeneous system. Biting forces are transferred from the mechanically stronger components of the system to the weaker system components. Under excessive strain, the weakest part of the system is the first to fracture and that is usually the root dentin.
5.1.1
Role of Ferrule Effect
All studies investigating the role of the amount of tooth structure enveloped by a crown, or fem1le effect, on all-ceramic restorations have so far focused solely on crowns luted with zinc phosphate cements9•15• With these luting agents, there is no chemical adhesion between the cement and the tooth or post. The resistance of crowns luted with zinc phosphate cements to occlusal forces was found to be significantly high er in restorations with a 2mm fen·ule6• Studies evaluating the role of fer rule design on adhesive cementation are not available (Diagram !).
\
; ''' "''''"'"""'"''""V'''C Dentin
Core
-
·�· · · · · · �· · --· ·
. . . . . .· ·. ·.I:.� r ule Diagram 1
5.2 Posts There is currently no definitive answer to the critical question of whether or not the placement of a post is still necessary for adequate core retention in light of the advanced adhesive technologies avail able today. In vivo studies on this subject are scarce, and most are plagued by the problem of poor comparability. Consequently, there are only general guidelines to aid the dentist in making the decision of whether or not to place a post in an endodontically h·eated tooth. These are described below. 61
Chapter 5
Non-vito/ Abutment Teeth
Indications For retention of a core in a tooth with insufficient tooth structure. •
Contraindications Availability of adequate tooth structure to retain a core Very narrow or tortuous tooth roots Short roots Inadequate seal of a root canal filling Periapical pathologies. •
• • •
•
Prerequisites for post and core placement Adequate root canal preparation technique Complete sealing of the root canal system using non-metallic sealing materials No or minimal exposure of the root canal filling to the oral cavity. • •
•
Complications Loss of retention of the restoration Caries Tooth fracture. • • •
5.2.1 Post Geometry The use of active posts (screw posts) is not recommended because their threaded design leads to increased distension stresses that could lead to root fracture10• 16• Passive post systems work by passive resist ance to withdrawal (tug-back) with no active exertion offorce. Cylindrical posts achieve good retention by means of friction, but they are too wide to fit in the apical region, where the roots usually become more narrow (Diagram2). Conical posts, on the other hand, have a more suitable geometry but poor retention. They also tend to wedge when force is applied (Diagram 3). Cylindro-conical posts were, therefore, developed to combine the advantages of the two forms. These hybrid posts are conical in the apical region and cylin drical in the coronal region.
62
5.2 Posts
I
Diogroms 2 ond
3
5.2.2 Post Materials Various types of materials are used to manufacture dental posts includ ing metals, ceramics and fiber-reinforced materials. For biologic rea sons, the only metals suitable for use as dental posts are gold and titani um. Other non-precious metals are subject to corrosion. The mechanical performance of metal posts is good, even when their diameter is small. Zirconia (see Chapter 1.2. 4) is the only ceramic post material available (Fig 1). Zirconia posts have high flexural strength, but, like all ceramics, they are very brittle. To achieve sufficient fracture resist ance, the diameter of ceramic posts must be slightly larger than that of metal posts. Metal and ceramic posts can be used for either direct or indirect restorations. The different types of fiber posts (Fig 2) differ in a number of ways. Glass or carbon fibers are embedded in a resin composite or epoxy resin matrix. The number and diameter of reinforcing fibers varies from one manufacturer to another. The mechanical properties of the different types of fiber posts vary accordingly. The modulus of elasticity of the various systems ranges widely, from roughly 20 to 320 GPa. Like all synthetic materials, fiber posts are susceptible to humidity and fatigue. Therefore, the mechanical data provided by the manufacturers apply only to brand-new fiber posts. Fiber posts are suitable for direct restorations only.
63
Chapter 5
Non-vito/ Abutment Teeth
Fig 1 Fracture surface of a zir conia post.
Fig 2 Fracture surface of a glass fiber post.
5.3 Esthetics Non-vital teeth may become discolored due to the presence of metal lic substances in root filling materials, blood degradation products, or degraded pulp proteins. Metal posts are also said to have a negative effect on tooth color and, thus, on the appearance of prosthodontic restorations. Esthetics may, therefore, be unacceptable for esthetically demanding restorations.
5.3.1 Bleaching of Non-vital Teeth The pros and cons of bleaching non-vital teeth must be carefully con sidered before starting such a treatment. One distinct advantage of non-vital bleaching is that, if successful, it may no longer be neces sary to place a crown on the non-vital tooth in order to obtain the desired esthetic result. If prosthetic rehabilitation is still required, bleaching will make the abutment more closely match the original tooth shade, thus creating more optimal conditions for the fabrication of an all-ceramic crown by a dental technician. Still, it is important to bear in mind that bleaching does not lighten discolored tooth roots, which often show through the gingiva. 64
5.3
Esthetics
The main disadvantage ofnon-vital bleaching is the risk of resorption at the root smface. Hydrogen peroxide, the most commonly used bleach ing agent, penetrates dentin5 and can cause external root resorption by vi11ue of its acidic pH4• It is, therefore, crucial to ensure that the root filling is reduced only 1 to 2 mm below the cementoenamel junction. As the root filling alone cannot completely prevent the diffusion of bleaching materials, glass ionomer cement is needed for additional sealing11 • The incidence of cervical root resorption was shown to increase when 30% hydrogen peroxide is used or when thermo-cat alytic bleaching is performed8.12. Therefore, it is generally recommend ed that internal bleaching be performed using sodium perborate mixed with water for mild to moderate staining, or with 3% hydrogen perox ide for severely discolored teeth. It is not always possible to eliminate tooth discoloration. The success of bleaching varies depending on the cause of discoloration. Unlike blood and protein degradation products, metallic products are very resistant to bleaching7•17• Also, the color stability of the bleaching result is not always assured. Discoloration relapse presumably occurs due to leakage through the restoration margins3• The more extensive the restoration of the affected tooth, the greater the chances that color pigments or bacteria will be able to penetrate the margins and cause a relapse of discoloration. After bleaching, the bonding strength of restorative materials to the tooth is temporarily reduced due to the presence of residual perox ide or oxygen. Optimal adhesion is achieved 3 weeks after bleach ing2·13. This time lapse can be used to check for color stability and to apply calcium hydroxide in order to buffer the acidic pH at the root surface (to prevent resorption).
65
Chapter 5
Non-vito/ Abutment Teeth
5.3.2 Effects of Posts on Tooth Color Non-tooth-colored posts are said to make the tooth and the marginal gingiva look gray and to impair esthetics. The color stability of four post materials (titanium, carbon fiber, glass fiber and zirconia), an opaque composite cement (Panavia21 OP, Kuraray Dental, USA), a composite core (Tetric C, Shade A3), and a ProCAD ceramic crown (CEREC) was recently investigated by our group (Sailer et al, in preparation). We did not observe any differences between the various types of post material with regard to color change in the root region. However, the differences between the different post materials were significant (Figs. 3 and 4). The type of post material influences the color of the crown (Figs. 5 and 6). We found that crown color is significantly dark er on titanium and carbon fiber posts covered by a ceramic layer thin ner than 1.5 m.m, whereas there is no significant difference when the ceramic layer is thicker than 1.5 mm. This mainly applies to the crown margins, where the layer thickness is often less than 1 .5 mm.
Fig 3 Titanium post with a composite core lshode A3l.
66
Fig 4 Zirconia post with o composite core (shade A3l.
Fig 5 Titanium post and core with a CEREC crown (shade A3l.
Fig 6 Zirconia post and core with a CEREC crown (shade A31.
5.4 Clinical Procedure
5.4 C l i n i c a l Procedures Preparations Chairside Rubber dam Dentin bonding agent Panavia 21 TC cement Set of drills Core composite Polymerization lamp. •
•
Tooth Isolate and dry the tooth Prepare a straight access to the root canal Prepare the post canal using drills of appropriate size, leaving at least 3 mm of gutta percha filling Rinse the canal with sodium hypochlorite solution (NaOCI) solution and dry with paper points (Fig 7) Insert the post into the prepared canal to the reference length to check for fit (Fig B) Check by radiography if necessary.
Fig 7 A paper point is used to dry the canol.
Fig 8 The post is inserted to the reference length to check for fit.
67
Chapter 5
Non-vital Abutment Teeth •
Post - Titanium posts: sandblast with 50 �m Al203 - Zirconia posts: condition with Clearfil Porcelain Activator and Clearfil SE BOND (Kuraray) Primer ( 1 : 1 )
Dentin Bonding If enamel etching is required, apply 37% phosphoric acid for 30seconds and then blow off and dry carefully (using paper points in the canal). Mix ED Primers A and B (Art Bond) at a ratio of 1 : 1 . Apply (also in the canal) with a brush and leave on for 60 seconds. Subsequent ly blow off and dry. Remove excess primer from the canal using absorbent paper points (Fig9). •
•
Cement Panavia 2 1 Mix cement ( 1 : 1 ) on a mixing pad Mix with a spatula for 30 seconds to fonu a homogeneous paste Grasp the post with diamond forceps and wet the lower 3 to 4 mm of the post with cement (Fig 1 0) Insert the post into the canal (Fig 11) Remove excess cement Apply Clearftl SE BOND to the entire dentin and enamel sruface, allow to take effect, blow off, and allow to harden for 60 seconds Build up the core with hybrid composite material (Fig 12). •
Fig 9 Application of primer. 68
Fig
10
Wetting of the post with cement.
References
View of the inserted post before core build-up.
Fig 1 1
Fig 12 View of the finished composite core.
References l . Bachicha WS, Difiore P, Miller PM, Lautenschlager EP, Pashley DH. Microleakage of endodontically treated teeth restored with posts. J Endodont 1998;24:703-708. 2. CavaUi V, Ries AF, Giannini M, Ambrosano GMB. The effect of elapsed time following bleacbi11g on enamel bond strength of resin composite. Operat Dent 200 I ;26(6):597-602. t 3. Friedman S. Inernal bleaching: Long-tem1 outcomes and complications. J Am DentAssoc 1997;128 (special issue):51-55. 4. Friedmann S, Rotstein I, Libfeld H, Stabholz A, Heling I. Incidence of external root resorption and esthetic results in 58 bleached pulpless teeth. Endodont Dent Traumatol 1988; 14:23-26. 5. Fuss Z, Szajkis S, Tagger M. Tubular pem1eability to calcium hydroxide and to bleaching agents. J Endodont 1989; 15(8):362-364. 6. Gelfand M, Goldman M, Sunderman E. Effect of complete veneer crowns on the compressive strength of endodontically treated posterior teeth. J Prosthet Dent 1984;52:635-638. 7. Glockner K, Ebelseder K. lndikationen und Grenzfalle fur das Bleicben von devitalen ve1farbten Frontziihnen Quintessenz 1993;44:519-527. 8. Heller D, Skriber J, Lin LM. Effect of intracoronal bleaching on external cer vical root resorption. J Endodont 1992; 18:145-148. 9. Isidor F, Odrnan P, Brondum K. ( 1 999) Intennittcd loading ofteeth restored using prefabricated carbon fiber posts. lnt J Prosthodont 1996;9: 13 1-136. 10. Milistein P L, Yu H, Hsu ES, Nathanson D. Effects of cementing on retention of a prefabricated screw post. J Prosthet Dent 1987;57:17 1-174. 69
Chapter 5
Non-vito/ Abutment Teeth
1 1 . Rotstein I, Zyskind D, Lewinstein I, Bamberger N. Effect of different protec tive base materials on hydrogen peroxide leakage during intracoronal bleach ing in vitro. J Endondont 1992; 18: 114-117. 12. Rotstein I, Friedman S, Mor C, Katznelson J, Sommer M, Bab I. Histological characterization of bleaching-induced external root resorption in dogs. J Endodont 1991; 17(9):436-441. 13. Shinohara MS, Rodrigues JA, Pimenta, LA. 1n vitro microleakage of compos ite restoration after noovital bleaching. Quintessence lnt 2001;32:413-417. 14. Sorensen JA, Engelman MJ. Ferrule design and fracture resistance of endodontically treated teeth. J Prostbet Dent 1990;63:529-536. 15. Standlee JP, Caputo M, Holocomb JP. The dentatus screw: Comparative stress analysis with other endodontic dowel designs. J Oral Rehabil 1982;9:23-33. 16. van der Burgt TP, Plaesschaert AJ. Bleaching of tooth discoloration caused by endodontic sealers. J Endodont 1986; 12:231-234. 17. Weiger R, Axmann-Krcmar D, Lost C. Prognosis of conventional root canal treatment reconsidered Endod Dent Traumatol 1998; 14( I): 1-9.
70
0> c:: ...c:: u ·-
0 Q) CQ 0
E
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Q) a_ 0
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71
Chapter 6
External Bleaching
6.1 Introduction Bleaching is defined as the decolorization and whitening of materials. Bleaching agents used in dental applications remove tooth discol oration by oxidizing chromogenic molecules. Vital tooth bleaching is distinguished from non-vital bleaching and is performed on the exter nal tooth swface.
6.1.2 Bleaching Agents •
•
Hydrogen peroxide (H202): Breaks down into oxygen and perbydroxyl radicals (0• und H02•). Carbamide peroxide (H2N-CO-NH2 H202): Reacts with water to form urea (6.6 parts) and hydrogen peroxide (3 .4 parts). •
6.1.3 Mechanism of Action Free 0• und H02• radicals diffuse through the organic substance ofthe interprismatic enamel and through the dentin. Perhydroxyl radicals (H02•) break down the large dark chromogenic molecules responsible for tooth discoloration into smaller unsaturated double-bonded mole cules that are lighter in color. After further oxidation, the molecules are converted into unpigmented, hydrophilic saturated carbon compounds.
6.1.4 Ind ications for External Bleaching • • •
72
Discoloration of the enamel Age-related tooth discoloration Mild to moderate tetracycline staining.
6.2
Power Bleaching
6.1.5 Contraind ications • •
Stains that can be removed by means of professional tooth cleaning Amalgam stains
Warning: Special caution is advised in patients with leaky fillings, hypersensitive teeth, large pulp cavities and/or exposed dentin.
6.2 Power Bleaching Power bleaching is an in-otiice procedure performed using highly concentrated bleaching agents. Light-activated catalysts are some times used to potentiate the bleaching reaction. Power bleaching is mainly performed to whiten a single discolored tooth or one specific area of a tooth. Generally, multiple sessions are required. Power bleaching products contain carbamide and hydrogen peroxide at con centrations of up to 35%1• The efficacy of using light-activation for potentiation of power bleaching has been variably described13•17. The application of high-intensity light also harbors the risk of overheating the pulp9•
6.2.1 Power Bleaching Procedure •
•
• •
Clean the teeth with an abrasive polishing paste in a rubber cup. (The custom of degreasing the teeth with alcohol or etching the enamel with phosphoric acid for this purpose is now obsolete). Determine and document the current shade of the teeth (photo graph the teeth together with the shade guide). Isolate teeth with a rubber dam. Apply the bleaching agent for approximately 5 minutes and wipe off with a cotton swab soaked in 3 % hydrogen peroxide; repeat for a tota.l of 4 to 6 times. Light activate the bleaching agent according to the manufacturer's instructions. Warning: take precautions to avoid overheating!
73
Chapter 6 External Bleaching •
•
• •
Subsequently apply colorless fluoride gel to the teeth. fluoride is used to restore the microhardness of the enamel and dentin, which is significantly diminished by the bleaching procedure, to the original bardness8. Depending on the results of whitening, the procedure may be repeated after about I month if necessary. Take a post-treatment photographic record. Restorative treatments should not be performed until at least one month after teeth whitening. This allows time for shade rebound'0 and for the elimination of oxygen remaining in the dental struc mre after bleaching, thus improving the bond strength of adhe sives to the bleached enamel and dentin2·15•
6.3 Combi ned B l e a c h i n g Combined bleaching is a method in which initial in-office cbairside bleaching is followed by subsequent at-home bleaching. This proce dure can be used to treat severely discolored teeth or to stabilize the results of in-office bleaching. However, it does not have any advan tage over at-home bleaching except for the initial acceleration of whitenint.
6.4 At- h o m e B l e a c h i n g This treatment modality is also referred to as "nightguard bleaching" or "mouthguard bleaching". In at-home bleaching, the patient applies a mild bleaching agent to the teeth using a custom tray. In the literature, 10% carbamide peroxide has been described as an effective and safe bleaching agent10•14. Its significant whitening effects were still detectable two years after teeth bleaching'6. Custom trays fabricated for nightguard bleaching should have gel reservoirs. Studies have shown that 52% of the bleaching gel remains in the reservoir 2 hours after application, and that 24% is still present 6 hours after applica tion11. 74
6.4
At-home Bleaching
6.4.1 At-home Bleaching Procedure Laboratory procedure (Figs I to 3) Fabricate a study cast (from the alginate impression provided by the dentist). Place a thin (approximately 0.5 mm) layer of block-out material on the labial tooth surfaces to create gel reservoirs. Do not block out the incisal edges, occlusal surfaces and a narrow zone along the gingival margin Use 0.5-mm-thick, soft tray material to vacuum-form a flexible, fom1-stable tray. The edges of the tray should follow the labial gingival contours, overlapping the oral gingival margin slightly to prevent leakage of the gel. •
•
•
•
I
Fig 1 Study cast with block-out material for gel reservoirs on the labial tooth surfaces.
Fig 2 The custom tray is trimmed and the edges rounded.
Fig 3 The tray follows the gingival contours.
75
Chapter 6
External Bleaching
Chairside procedure (Figs 4 to 9) Clean the teeth with an abrasive polishing paste in a rubber cup Determine and document the current tooth shade (photograph the teeth together with the shade guide) Adapt the tray for optimal fit Provide the patient with instructions on how to use the tray and gel bleaching system. Instructions for use: First brush and floss the teeth with toothpaste and dental floss Dispense dabs ofwhitening gel into the reservoirs of the tray Seat the tray over the teeth. Gently press the tray against the teeth Remove excess gel with a toothbrush or a cotton swab Refrain from eating and drinking while the tray is in place t teeth with a toothbrush and water After removing the tray, clean he Subsequently rinse the teeth with a colorless fluoride solution8 Clean the tray with a toothbrush and water Avoid smoking and foods that will stain teeth for the entire duration of treatment The patient should be informed about potential side effects, such as reversible tooth sensitivity and gingival irritation3•5•1w. The patient should be aware of how to alleviate these symp toms, e.g., by applying desensitizing gel. The patient should be issued with enough whitening gel for one week of treatment. First week: the whitening gel is initially applied for 2 hours to test for side effects. If no side effects occur, the gel is applied overnight for 8 hours. Frequently replacing the bleaching agent increases the risk of side effects7• The patient should return for a follow-up visit after 1 week. If there are no problems, overnight bleaching can be continued. The duration of treatment is generally 2 weeks for mild to moder ate staining'0, and up to 6 months for tetracycline staining12• The bleaching result should be assessed and documented. Restorative treatments should not be performed until at least l month after teeth whitening. This allows time for shade rebound10 and for the elimination of oxygen remaining in the dental struc ture after bleaching, thus improving the bond strength of adhe sives to the bleached enamel and dentin2·'5• •
•
•
•
•
•
•
•
•
•
•
76
6.4 At-home Bleaching
Fig 4 Tooth cleaning.
Fig 5 Pretreatment photographic record with reference shade.
Fig 6 Dabs of gel are dispensed into the . reservoars.
Fig 7 Excess gel is subsequently removed.
Fig 8 View of the seated tray.
Fig 9 Post-treatment photographic record with reference shade.
77
Chapter 6
External Bleaching
6.5 "Over-the-cou n ter" Teeth Whitening Over-the-counter (OTC) teeth whitening systems are freely available on the market. The manufacturers promise their customers "white" teeth.
6.5.1 OTC Bleaching Kits ore bleaching kits generally consist of an acidic oral rinse (acetic acid or citric acid), a prefabricated tray that can only be adapted to a limited degree, 3 to 6 % hydrogen peroxide bleaching gel, and an abrasive toothpaste. Because of the poor fit of the tray, the bleaching gel leaks, is swallowed and is quickly inactivated by saliva. ln addi tion, the procedure is very abrasive. The use of such kits cannot be recommended.
6.5.2 Whitening Strips Whitening strips are transparent, self-adhesive strips of adjustable plastic that have been coated on one side with bleaching agent. They are generally worn for 30 minutes a day, twice daily, for a period of 2 weeks. The most commonly used bleaching agent is 6 % hydrogen peroxide. Whitening strips produce demonstrable teeth whitening effects, and the side effects tend to mild and reversible6• The cost-effec tiveness ratio of whitening strips is attractive to consumers.
6.5.3 Teeth Whitening Toothpastes Toothpastes do not have a bleaching effect because hydrogen perox ide and carbamide peroxide are incompatible with the other ingredi ents in these products. At best, they work through microabrasion or concealing effects.
78
References
6.5.4 Whitening Chewing Gums The active ingredients in whitening chewing gums are quickly diluted by saliva. Furthermore, the whitening agents are rapidly inactivated by salivaty peroxidases.
References I. Al Shetberi S, Matis BA, Cochran MA, Zekonis R, Stropes MA. Clinical eval
2.
3.
4.
5. 6. 7.
8.
9. 10. II.
12.
uation of two in-oftice bleaching products. Oper Dent 2003;28(5):488-495. Cavalli V, Reis AF, Giannini M, Ambrosano GM. The effect of elapsed time following bleaching on enamel bond strength of resin composite. Oper Dent 200 I ;26(6):597-602. Da Costa Filho LC, Da Costa CC, Soria ML, Taga R. Effect of home bleaching and smoking on marginal gingival epithelium proliferation: A histologic study in women. J Oral Pathol Med 2002;31 (8):473-480. Deliperi S, Bardwen DN, Papathanasiou A. Clinical evaluation of a combined in-office and take-home bleaching system. JAm Dent Assoc 2004; 135(5):628634. Fugaro JO, Nordahl I, Fugao, OJ, Matis BA, Mjiir IA. Pulp reaction to vital bleaching. Oper Dent 2004;29(4):363-368. Gerlach RW, Gibb RD, Sage! PA. Initial color change and color retention with a hydrogen peroxide bleaching strip. Am J Dent 2002; 15( I ):3-7. Leonard RH Jr, Haywood VB, Phillips C. Risk factors for developing tooth sensitivity and gingival irritation associated with nightguard vital bleaching. Quintessence lot 1997;28(8):527-534. Lewinstein l, Fuhrer N, Churaru N, Cardash H. Effect of different peroxide bleaching regimens and subsequent fluoridation on the hardness of human enamel and dentin. J Prosthet Dent 2004;92(4):337-342. Luk K, Tam L, Hubert M. Effect of light energy on peroxide tooth bleaching. .T Am Den!Assoc 2004;135: 194-201;Quiz 2. Matis BA, Cochran MA, Eckert G, Carlson TJ. The efficacy and safety of a 10% carbamide peroxide bleaching gel. Quintessence Int 1998;29(9):555-563. Matis BA, Gaiao U, Blackman D, Schultz FA, Eckert GJ. lu vivo degradation ofbleaching gel used in whitening teeth. J Am DentAssoc 1999;130(2):227235. Matis BA, Wang Y, Jiang T, Eckert GJ. Extended at-home bleaching of tetra cycline-stained teeth with different concentrations of carbamide peroxide. Quintessence Int 2002;33(9):645-655.
79
Chapter 6
External Bleaching
13. Papathanasiou A, Kastali S, Perry RD, Kugel G. Clinical evaluation of35% hydrogen peroxide in-office whitening system. Compend Contin Educ Dent 2002;23(4):335-344;Qu.iz 348 14. Rosenstiel SF, GegautfAG, Johnston WM. Randomized clinical trial of the efficacy and safety of a home bleaching procedure. Quintessence lnt 1996;27(6):413-424. 15. Spyrides GM, Perdigao J, Pagani C, Araujo MA, Spyrides SM. Effect of whitening agents on dentin bonding. J Esthet Dent 2000;12(5):264-270. 16. Swift EJ Jr, May KN Jr, Wilder AD Jr, Heymann HO, Bayne SC. Two-year clinical evaluation of tooth whitening using an at-borne bleaching system. J Esthet Dent 1999; 1 1 ( 1 ):36-42. 17. Tavares M, Stultz J, Newman M, Smith V, Kent R, Carpino E, Goodson JM. Light augments tooth whitening with peroxide. J Am Dent Assoc 2003;134:167-175.
80
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81
Chapter 7
All-ceramic Fixed Partial Dentures
7.1 General Considerations The desire for the development of all-ceramic bridges is primarily driven by the fact that the esthetic result of all-ceramic restorations surpasses that of metal-ceramic restorations. Ceramic materials also have the advantage of better biocompatibility and low thermal con ductivity. Regarding the physical properties of the available ceramic materials (see Chapter 1), glass-infiltrated ceramics and high-strength ceramics are the only suitable candidates for the fabrication of all ceramic bridges. Yttrium-stabilized zirconia is a particularly interest ing material that is increasingly being used as the framework for both posterior and anterior all-ceramic bridges.
7.2 I n dications Owing to the low mechanical strength of ceramic materials, fixed par tial dentures with ceramic frameworks can only be placed in regions where no excessive occlusal forces can be expected. The feasibility of all-ceramic fixed partial denture restorations is determined by the fol lowing factors (seeflow chart 1): Expected occlusal forces (anterior and posterior restorations) Span (three-unit or multi-unit) Amount of space required for the restoration (framework dimen sions) Stump shade. •
• •
•
The best esthetic results are obtained with glass-infiltrated ceramics owing to their superior optical properties. As the superior esthetic appeal of glass-infiltrated ceramics is due to their translucency, the appearance of this material is influenced by the shade of the underlying abutment. Therefore, the abutment below a glass-infiltrated ceramic 82
7.2
Indications
should ideally be dentin-colored. High-strength ceramics are more opaque than glass-ceramics so they are able to cover discolored abut ments better, but still not completely. Consequently, the shade of the prepared abutment does not affect the esthetic appearance of high strength ceramic restorations as much as that of glass-ceramic restora tions.
Span
/ Short (3 to 4 units)
Long (5 o r more units)
I No rmal occlusal forces
I
Excessive occlusal forces
.
Zirconia
Metal-ceramic
Metal-ceramic
Decision process for the choice of fixed partial dentures loll-ceramic versus metal-cera m id.
Diagram 1
83
Chapter 7 All-ceramic Fixed Portio/ Dentures
7.3 Tooth Preparation The tooth preparation guidelines for all-ceramic bridges are the same as those for all-ceramic crowns (see Chapter4). The parallelism of the abutment teeth integrated in the restoration must naturally be respected. The amount of vertical clearance is another important factor. Mechani cally, the connector area is the primaty weak point of any ceramic fixed partial denture. Basic research has shown that the initial crack that ulti mately leads to the failure of all-ceramic fixed partial dentures invari ably starts at the connectors in the gingival region4•8. Connector width requirements were calculated based on these data (Diagram !). The marginal and internal fit of CAD/CAM all-ceramic fixed par tial dentures is slightly inferior than that of metal-ceramic fixed partial dentures, but is well within the clinically acceptable range7•10•12,14•
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7.4
Dental Laboratory and Dental Office Procedure
7.4 Denta l La boratory a n d Dental Office Proced u re Two processes are generally used for the fabrication of zirconia frameworks for fixed partial dentures. With the first process (e.g. Cercon Smart Ceramics, Degudent, Hanau, Germany), the dental technician first uses a master model to fabricate a fixed partial denture framework according to the conven tional lost wax technique2• The wax frame is then removed from the master model and scanned by the system's scanner. The CAM unit then automatically mills the framework from a presintered "green" zirconia block. Green zirconia is porous and softer than densely sin tered zirconia. Consequently, the milling time is significantly shorter and smaller wear of the milling burs occurs. Moreover, it is also pos sible to make fme adjustments by hand when zirconia is still in the green stage. The framework is subsequently placed in the sintering furnace and fired at 1350°C for 6 hours. The sintering process leads to 20% shrinkage and densification of the material. In order to match the dimensions of the original working dies, the framework milled from the green material must be oversized accordingly to compen sate for the sintering shrinkage. The second process (e.g. DCS, Allschwil, Switzerland) uses the same wax-up and scanning procedures, but mills the framework from densely sintered zirconia blanks 1• True CAD/CAM systems allow the user to fabricate ceramic fixed partial denture frameworks without having to physically model a wax pattern. One CAD/CAM system (Procera) has a mechanical scanner that scans the prepared abutment, the adjacent teeth, the basal surface of the connector, and the opposing arch15• The scan data are then trans mitted to a computer. The laboratory technician can then digitally design the framework on-screen. When fmished, the digitized data are transferred electronically to a milling center. The milling center fabri cates the zirconia framework and sends it to the dental laborat01y for further processing and veneering.
85
Chapter 7
All-ceramic Fixed Partial Dentures
As zirconia cannot be soldered conventionally or by laser, the fmished zirconia frameworks cannot be separated and reconnected. Zirconia frameworks, therefore, require meticulous design planning. The fol lowing guidelines apply to all systems and techniques used for fabri cation of zirconia frameworks for fixed partial dentures: • •
•
• • •
Minimum framework wall thickness: 0.4mm Milling of the framework must be perfonned while cooling with water (to prevent the fonnation of microcracks)3.6 The framework is sandblasted with 50 to I I 0 �tm aluminum oxide particles at a jet pressure of 2 to 4 bar and a distance of approxi mately I em 5 The framework is cleaned in an ultrasound bath Firing is performed at I 1 00°C During firing, the bridge should be positioned on thin wires to prevent thermal stress (NB: The thennal conductivity of zirconia is low).
Regarding connector design, the minimum connector width to prevent fixed partial denture fracture is 9 mm2 for three-unit bridges and 1 2 mm2 for four-unit bridges8• Furthermore, the connector should have a large radius of curvature at the gingival embrasure (Dia gram 2)9. The guidelines for fabrication of zirconia frameworks are otherwise the same as those for metal frameworks. Like metal fixed partial denture substructures, zirconia frame works are tried in so that subsequent fitting adjustments can be made as needed. Final cementation may be carried out adhesively or con ventionally (see Chapter B). The radiopacity of zirconia frameworks is also clinically useful as this allows for radiological control of fit (Figures 1 through 13).
86
7.4
Dental Laboratory and Dental Office Procedure
Four-unit zirconia fixed partial denture (teeth 14-x-x- 17)
Fig l Pretreatment radiograph of the situation in the right maxilla. Tooth 16 is not worth preserving. An all-ceramic four-unit fixed partial denture lteeth 17-x-x-14) with a zirconia framework is planned.
Fig 2 View after extraction of tooth 16.
Fig 3 Teeth 17 and 14 were prepared as the abutments to support the four-unit bridge.
Fig 4 The diagnostic wax-up fabricated by the dental technician is tried in to check the final esthetics and function. 87
Chapter 7
All-ceramic Fixed Portio/ Dentures
Fig 5 The silicone index is used to check the wax model of the planned restoration for form and design.
Fig 6 View of the densely sintered zirconia framework. Note the basal curvature of the connector design.
Fig 7 Like metal fixed partial den ture frameworks, the zirconia frame work is checked for fit and design dur ing try-in.
Fig 8 Shade selection is performed accord ing to the criteria and procedure described in the chapter on all-ceramic crowns.
88
Fig 9 It is helpful to apply a liner when selecting the color for zirconia frameworks. This makes it easier to determine the tooth hue, chroma and value.
7.4
Dental laboratory and Dental Office Procedure
Figs lOa and lOb Occlusal and basal views of the finished fixed partial denture.
Fig 1 1 The milled zirconia framework in the green stage next to a densely sintered one {a second framework was manufactured for demonstration purposes!. The size differ ence is clearly visible on direct comparison.
Fig 12 Try-in of the fin ished zirconia bridge. In terms of shape and color, the restoration blends well with the surrounding natural dentition.
Fig 13 Radiographic control of the fixed partial denture after cemen tation with glass ionomer cement. The zirconia framework appears as a radiopaque structure. 89
Chapter 7
All-ceramic Fixed Partial Dentures
7.5 C l i n ica l Surviva l Rates A systematic review of the literature was recently performed to assess the clinical survival rates of all-ceramic fixed partial dentmes followed for a minimum period of 3 years. Although the results were encourag ing, the failure rate of all-ceramic fixed prutial dentures was signifi cantly higher than that of conventional metal-ceramic fixed partial dentures. Specifically, the annual failure rate for all-ceramic bridges was 4%11 compared with an annual failure rate of only 0.4% for metal ceramic bridges13. All of the ceramic frameworks studies were fabri cated using either glass-ceramic (Empress II) or glass-infiltrated ceramic materials (Jn-Ceram Alumina, ln-Ceram Zirconia). This is a particularly relevant fact to note as neither of these two materials belongs to the class of high-strength ceramics. Consequently, it is not possible to assess the chances of success of all-ceramic fixed partial dentures with frameworks made of zirconia based on these data. Three-year follow-up studies of all-ceramic fixed partial dentures with zirconia frameworks have not yet been published in the litera ture. Ofthe zirconia fixed partial denture studies described in talks or posters presented at symposia, it is a promising sign of clinical stabil ity that no framework failures have been repotted to date. The data from our clinic confirms this impression. Framework fractures have not occurred in any of our 36 patients with a total of 46 zirconia fixed partial dentures who were followed for a period of 3 years. However, one patient fractured the zirconia fixed partial denture in an "chewing accident" (by biting on a stone in his food) 38 months after the fixed pattial denture placement. In summaty, one can conclude that fixed partial dentures with zir conia frameworks have met stability expectations with regard to with standing occlusal forces in the posterior region during masticatory function. However, they should be used with restraint in practice because no true long-term data are available.
90
7.6
Conclusions
Regarding potential failures and complications, one can basically expect the same type of events that occur with metal-ceramic restora tions to occur in all-ceramic fixed partial denhtres with zirconia frame works. •
Biologic Caries Periodontitis Devitalizationlperiapical pathologies.
•
Technical Tooth fracture Build-up fracture Framework fracture Veneering fracture Loss of retention.
•
Esthetic Discoloration - Gingival recession.
7.6 Concl usions All-ceramic fixed partial dentures with zirconia frameworks are an interesting and promising alternative to conventional metal-ceramic fixed partial dentures. In light of the intensive research efforts in this field, further developments and improvements can be expected. Once these improvements and adequate long-term follow-up data become available, one can hope that all-ceramic fixed partial dentures with zir conia frameworks will become a true alternative to metal-ceramic fixed partial dentures in the posterior region.
91
Chapter 7
All-ceramic Fixed Portio/ Dentures
Refere nces 1. Besimo CE, Spielmann HP, Rohner HP. Computer-assisted generation of all ceramic crowns and fixed partial dentures. Int J Comput Dent 200 I ; 4(4):243-262. 2. Feher A, Egger B, Luthy H, Schumacher M, Loeffel 0, Scharer P. ISO Zementevaluation und klinische Untersuchung von Zirkonoxidstiftautbauten. Acta Med Dent Helv 1999;4:20 1-209. 3. Guazzato M, Quach L, Albakry M, Swain MV. Influence of surface and heat treatments on the flexural strength ofY-TZP dental ceramic. J Dent 2005; 33(1):9-18. 4. Kelly JR, Tesk JA, Sorensen JA. Failure of all-ceramic fixed partial dentures in vitro and in vivo: Analysis and modeling. J Dent Res 1995; 74(6): 1253-1258. 5. Kosmac T, Oblak C, Jevnikar P, Funduk N, Marion L. The effect of surface grinding and sandblasting on flexural strength and reliability of Y-TZP zirco nia ceramic. Dent Mater 1999;15(6):426-433. 6. Kosmac T; Oblak C, Jevnikar P, funduk N, Marion L. Strength and reliabllity of smface treated Y-TZP dental ceramics. J Biomed Mater Res 2000; 53(4):304-3 13. 7. Le Tran D. Marginale und interne Passgenauigkeit computergestutzt gefer tigter vollkeramischer Briickengeriiste. Dissertation, University of Ziirich: 2003. 8. Luthy H, Filser F, Loeffel 0, Schumacher M, Gauckler LJ, Hiinunerle C. Strength and reliability of four-unit all-ceramic posterior bridges. Dent Mater 2005;2 1 ( 10):930-937. 9. Oh W, Gotzen N, Anusavice KJ. Influence of connector design on fracture probability of ceramic fixed-partial dentures. J Dent Res 2002;81(9):623-627. 10. Reich S, Wichmann M, Nkenke E, Proescbel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005; I 13(2): I 74-179. 1 1 . Sailer I, Pjetursson BE, Zwahlen M, Hammerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal-ceramic recon structions after an observation period of at least 3 years. Part II: Fixed dental prostheses. Clin Oral Imp! Res 2007; 18(Suppl.3):86 96. 12. Stappert CFJ, Dai M, Chitmongkolsuk S, Gerds T, Strub JR. Marginal adapta tion of three-unit fixed partial dentures constructed from pressed ceramic sys tems. Br Dent J 2004;1 96:766-770. 13. Lang NP, Pjetursson BE, Tan K, Bragger U, Egger M, Zwahlen M. A systemat ic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clin Oral Implants Res 2004; 15(6):643-653. 14. Tinscbert J, Natt G, Mautsch W, Spiekermann H, Anusavice KJ. Marginal fit of alumina-and zirconia-based fixed pa11ial dentures produced by a CAD/CAM system. Oper Dent 2001 ;26(4):367-374. 15. Zitzmann NU, Marinello CP, Luthy H. The Procera Allceram all-ceramic sys tem. The clinical and technical laboratory aspects in the use of a new all ceramic system. Schweiz Monatsschr Zahnmed 1999; I 09(8):820-834. -
92
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93
Chapter 8
Bonding of Ceramic Restorations
8.1 Ad h esive versus Conventio n a l Cem entation Adhesive bonding is crucial to the clinical success of all-ceramic restorations6. In this context, four major factors play a role: Fracture strength Retention Microleakage Translucence
• • •
•
8.1.1 Fracture Strength Adhesive bonding increases the fracture strength of all-ceramic restorations. In one in vitro study, the fracture strength of all-ceramic crowns luted by adhesive bonding was found to be just as high as that of metal-ceramic crowns2'. For ceramics with low material strength, the strengthening effect of adhesive bonding results in significant improvement of long-term clinical performance. Clinical studies have demonstrated that the survival rates of adhe sively bonded glass-ceramic restorations are significantly higher than those of conventionally cemented restorations12·16• 17•19• This superior clinical performance is attributable not only to a reduced rate of fracture occurrence, but also to a reduced rate of reten tion loss23• One crucial prerequisite for clinical success is proper con ditioning of the ceramic restoration and the tooth surface prior to bonding. The purpose of conditioning is to increase the bonding sur face area in order to improve mechanical retention and to enhance the quality of chemical coupling between the cemented components. The bonding procedure for glass-ceramics and oxide ceramics differ due to differences in their compositions (see Chapters 7. 3 and 7. 4). The need for adhesive bonding of oxide ceramics is disputed due to thei.r high material strength. As clinical experience with these ceramics is still relatively short, there currently are no studies demonstrating whether or not conventional cementation and adhesive bonding result in comparable survival rates. Moreover, the choice of cementation system for oxide ceramics is influenced by another imp01tant factor; retention of the restoration. 94
8.1
Adhesive Bonding versus Conventional Cementation
8.1.2 Retention CAM of restorations from densely sintered or presintered ceramic blocks results in a lower accuracy of internal fit than in ceramic restorations fabricated by layering or pressing techniques20• In vitro studies show that the marginal and internal gaps in CAD/CAM-gener ated all-ceramic crowns are larger than those of porcelain-fused-to metal crowns'. Ceramic restorations, therefore, have lower retention. Consequently, conventional cementation of ceramic restorations fre quently results in a loss of retention, whereas adhesive bonding is not affected by this problem23•
8.1.3 Microleakage The degree of marginal integrity is determined by the size of the mar ginal gap and the strength of the bond between the luting agent and the restoration or tooth, respectively. Microleakage at crown margins promotes the penetration and passage of bacteria to the pulp. This bacterial invasion can lead to a loss oftooth vitality8. Further potential complications of marginal leakage are secondary caries, periodontal problems, and a loss of esthetics due to marginal discoloration. In vitro studies have shown that the amount of microleakage is signifi cantly lower in restorations bonded with composite cements com pared with those luted with conventional zinc oxide phosphate cements8•924• In particular, conventional cementation leads to a higher loss of marginal integrity of CAD/CAM-generated all-ceramic restorations than of metal-ceramic restorations1•
8.1.4 Tra nslucency The optical and color characteristics of the luting material affect the final esthetics of translucent ceramics more than they affect the opaque ceramics (see Chapter 2.3). Consequently, the use of more opaque cements (e.g., phosphate cements) leads to a stronger increase in the opacity of glass-ceramics compared with of alumina ceramics. Inversely, the use ofa translucent composite increases the translucency of all-ceramic materials (including zirconia)'. An explanation for this 95
Chapter 8
Bonding of Ceramic Restorations
could be that the cement improves the flow of light through the ceram ic material. The use of conventional cement for luting of all-ceramic restorations is, therefore, contraindicated for esthetic reasons.
8.2 Classification of Ad h esive Cements 8.2.1 Com position The composition of resin composite cements is basically the same as that of composite filling materials: Matrix: mixture of bisphenol A glycidyl methacrylate (Bis-GMA) and low-viscosity additives such as triethylene glycol dimethacry late (TEGMA) resin and urethane dimethac1ylate (UDMA) resin Filler: lithium/barium borosilicate, Si02 Curing agent: Light-cured, self-curing or dual-cured. •
• •
The silanized inorganic fillers embedded in the matrix are mainly responsible for the mechanical characteristics of resin composite cements. Due to technical reasons related to differences in material processing, the physicochemical properties ofresin composite cements differ from those of resin composite fillings as follows: Catalyst reduction: longer working time Filler size reduction: minimal layer thickness Reduced filler content: improved :flowability Opacifying additives: reduced translucence. •
• • •
In most cases, an additional adhesive is required to achieve a bond between resin composite cements and dentin. Adhesive monomers found in adhesives and composite cements include: 2-hydroxyethyl methacrylate (HEMA) 4-methaciyloxyethyl trimellitate Phosphate monomers, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) •
•
•
Resin composite cements containing adhesive phosphate monomers should always be used to cement ceramic materials that cannot be etched or are difficult to etch. Adhesive phosphate monomers are required to achieve the necessary adhesion to these ceramic materials13• 96
8.2
Classification of Adhesive Cements
8.2.2 Cha racteristics of Resin Com posite Cements Resin composite cements are insoluble in saliva. As shown below, their physical characteristics show a wide range of product-specific variabiljty2. Curing time: 2 to 7 minutes <25 1-!m Film thickness: Flexural strength: 70 to l72MPa (24h) Modulus of elasticity: 2.1 to 3.1 GPa Water solubility 0 to 0.01 % Moderate Pulp reaction: •
•
•
• •
•
Rely X U nicem (3M Espe, Seefeld, Germany)
Dual-curing universal resin cement Powder Glass powder (silanized) Initiator Silica ( silaruzed) Substituted pyrimidine Calcium hydroxide Peroxy compound Pigment. •
•
Liquid Methacrylated phosphoric acid ester Dimethacrylate Acetate Stabilizer Initiator.
Panavia® 21 ( Kurarayl
Self-curing composite resin Bis-GMA Phosphorylated methacrylate resin groups • •
97
Chapter 8
Bonding of Ceramic Restorations
Voriolink II !Vivodent, Schoon, Liechtenstein) Dual-curing composite cement Matrix: Bis-GMA, urethane dimethacrylate, triethylene glycol dimethacrylate Filler: Barium glass, ytterbium tluoride, Ba-Al fluorosilicate glass, spheroidal mixed oxides (mean filler size: 0.7 Jlm). •
•
8.2.3 Req u i rements The "ideal" resin composite cement should meet the following clini cal requirements: High translucency Good mechanical properties (high compressive strength and flexural strength) High bond strength Low solubility Suitable viscosity (maximal filler content to still maintain flowa bility) Ease of handling Radiopacity. • •
•
• •
• •
8.3 Dentin Conditi o n i n g 8.3.1 Pre-treatment of the dentin after preparation After tooth preparation, the cut dentin should be protected from: Mechanical forces (manipulation of the temporary, impressioning, etc.) Chemicals (dental materials) Bacteria (bacterial microleakage) Thermal stresses (cold, heat). A range of products are available for the conditioning of freshly pre pared dentin. These can be divided into two groups according to their mode of action: •
• • •
98
8.3
Dentin Conditioning
Desensitizing agents •
•
Obliterate dentinal tubules by means of coagulation necrosis (e.g.,Ca(OHh) or by precipitation ofCa2+-, POl and proteins after application of a glutaric dialdehyde primer (e.g., Gluma®) Do not affect the dentin bond strength of adhesives.
Sealing agents •
• •
Coverage of dentin and obliteration of dentinal tubules is achieved through application of primer and bonding agent Increase the bonding strength before adhesive cementation> Single-component (one-bottle) systems do not achieve adequate sealing22•
The selected product must be compatible with the luting cement. Incompatibility leads to a decrease in bond strength (smear layer). Optimal dentin adhesion can only be achieved when the bonding agent is applied to freshly prepared dentin'5• For this reason, the dual bonding technique is still used today'8. Considering the chemical dif ferences in cements, it is important to use the correct bonding system to seal the tooth after preparation. If, at this time, it is still unclear which ceramic material (and thus which type of cement) will be used, the prepared dentin should only be desensitized with a glutardialde hyde-containing primer (Gluma®) as a precautionary measure. 8.3.2 Dentin Conditioning Before cementation, the dentin is conditioned with the appropriate kit component(s) according to the manufacturer's instructions. Glass-ceramics: Syntac Classic (Ivoclar) Oxide ceramics (high-strength ceramics) Clearfil SE Bond (Kuraray), ED Primer (Kuraray) • •
Ifthe type ofcement to be utilized is known at the time of tooth prepa ration, the corresponding bonding system can be used to seal the dentin according to the dual bonding technique.
99
Chapter 8
Bonding of Ceramic Restorations
8.4 Cera m i c Cond itioning Chemical bonds between resin composite and glass-ceramics are achieved by means of coupling molecules, for example, silane. Silane bonds with silicates in the glass matrix of the ceramic material (inor ganic substance) on the one side, and polymerizes with the organic matrix of the composite resin on the other. In order to be chemically active, the silane molecules must be hydrolyzed to silanol. Distinctions are made between one and two component systems. Single-component silanes, which are more fre quently used in clinical practice, are already hydrolyzed. Their expira tion date must be strictly observed as they become inactive with time. (Please note, the fluid must be clear. Discard if cloudy). In the case of glass-infiltrated ceramics, etching alone does not achieve sufficient surface roughening. Therefore these ceramics must be sandblasted (with 50 to 100 11m Al203 at 2.5 bar). Although ceramic conditioning does not increase bond strength, it does improve wetta bility'4. Glass-infiltrated ceramics should be cemented with a phos phate monomer-based cement (see Chapter 7.2. 1). Oxide ceramics contain few or no silicates, and they cannot be silanized in the same manner as glass-ceramics. New resin composite cements (e.g., Panavia 2 1 ) contain an adhesive phosphate monomer (e.g.,MDP) that can bond to oxides, thus making it possible to achieve chemical bonding of oxide ceramics with or without the use of an adjunctive bonding agent. However, application of an adjunctive bonding agent does improve the long-term stability of bonding and, is therefore, recommended4• As with metals, the improved chemical bonding must be achieved either by means ofsilica coating (RocatecTM system, Minnesota, USA) and subsequent silanization or without silica coating using special adhesive silanes (with adhesive phosphate monomers).
100
8.5 Clinical Procedure
8.5 Clinical Procedures 8.5.1 Ind ications a n d Recommended Materials
Gloss-ceramics
Co.m:litionina
Etching 9.5% hydrofluoric acid Silonizotion IMonobond Sl
B.ondiiJQ.
Cement
Gloss-infiltrated cerom1cs
Sandblasting 100 [J.m Al203, 2.5 bar
Cleorfil SE Bond lor ED Primerl
Ponovio 21
Oxide ceramics !alumino, zirconiol
Sandblasting 100 p.m Al203, 2.5 bar Silonizotion ICiearfil Porcelain Activator!
Cleorfil SE Bond lor ED Primer!
Ponovio 21
'
Syntoc
Vortolink II
8.5.2 Step-by-step Procedure a. Glass-ceramics
The step-by-step procedure for adhesive bonding of anterior ceramic crowns (Creapress®) is described by way of example.
The preparation for vital tooth 1 1 is circular with o 1 m m wide shoulder and rounded edges, ensuring o minimum loss of tooth struc ture. Because the stump shade is ideal, the tooth con be restored using o translucent gloss-ceramic. Adhesive bonding increases the fracture strength of ceramic restorations. For this reason, adhesive bonding should performed with due diligence. A thin retraction cord INo. OOO.OOl should be placed before adhesive luting whenever possible.
Fig 1
1 01
Chapter 8
Bonding of Ceramic Restorations
to 2c The pressed and sin tered dentin core of optimal color and translucency is veneered to match the optical charac teristics of the adja cent teeth. Anterior and posterior views of the crown.
Figs 2a
The internal surface of the crown is etched with 9.5% hydrofluoric acid (for example Ultradent'-" Porcelain Etch, Utha, USA) for 60seconds. !NB: Gloves and protective glass must be worn!l. The hydrofluoric acid is then rinsed off with running water. To remove etching precipitates, the crown is ultrasonically cleaned in alcohol for 4 minutes. Alterna tively, it can be etched again with a weaker acid !phosphoric acidl for 30seconds.
Figs 3a and 3b
102
8.5 Clinical Procedure
Figs 4a and 4b Scanning electron micrograph and 3D views of on ideally etched (l minuteI gloss-ceramic. Significant surface area enlargement and numerous tunnels are clearly visible.
5
Fig The internal surface of the etched and cleaned crown should hove a matte appearance without white deposits to ensure that the roughened surface shown in Figures 4a and 4b can be optimally used for cementation.
Fig 6 Silanization is then performed for example using Ultrodent® Silane or Monobond S. !NB: Compati bility with the cement is im perative!) The silanized crown should now be completely free of contami nants (moisture, alcohol, etc.l. Once the sol vent has evaporated (after about l minute!, a bonding agent is applied to the internal surface of the crown, and the crown is stored in a dark place.
103
Chapter 8
Bonding of Ceramic Restorations
Figs 7 and 8 A dentin bonding agent ISyntac primer, adhesive and bonding agent, Con necticut, USAI is applied to the prepared tooth according to the manufacturer s instruc tions. The thin coat of bonding agent gives the conditioned stump a slightly glossy appear ance. '
Fig 9 Variolink II !lvoclar Vivadentl is sup plied in two consistencies llow and high vis cosity) and in four shades. To reduce the occurrence of microleakage, the more high ly filled and more highly viscous types should be used whenever possible. Vori olink II can be dual-cured I base + catalyst) or only light-cured I basel. When lutin g all ceramic crowns with thick layers of ceramic material, the dual curing variant should be used in order to ensure complete curing of the cement in the deep layers. For optimal esthetics, the transparent cement should be used.
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50 u.m • Fig lOa Bose and catalyst paste of the some shade !ideally transparent) are mixed at a ratio of l 1 and applied to the crown with a brush. :
104
Fig lOb Scanning electron micrograph showing the bond between the conditioned ceramic Itop) and Variolink II lbottoml. The cement contoins various fillers of different sizes !hybrid fillers!.
8.5 Clinical Procedu re
Fig 1 1 After correct placement of the crown, excess cement is carefully removed with foam pellets and dental floss. Glycerin gel should be applied around the crown margins in order to prevent oxygen inhibi tion (i.e., the absence of curing in the resin composite Ioyer exposed to oxygen I. Poly merization is then initiated for l minute on the buccal, palatal, and incisal surfaces and also when the dual curing variant is used. Although it tokes up to roughly 24 hours for the cement to cure in the deep er ceramic layers, the excess cement is removed immediately. -
Figs 12 to 14 Hardened residual cement is carefully removed with on ex p lorer or scaler while gently manipulating the gingiva. The retraction cord is su bsequently removed, which con bring out some additional cement residue. The margin of the crown is finally carefu lly finished (e.g., with o covosurfoce bevel!. Radiological control of residual cement is difficult due to its low radiopacity .
105
Chapter 8
Bonding of Ceramic Restorations
b. Oxide ceramics This procedure is illustrated based on a case example (zirconia crown placement). Clinical situation after the prepara tion of a gold post-retained crown on tooth 11. As the old post could not be removed without endangering the root I risk of fracture!, it was included in the prepara tion. To achieve an esthetic restoration, the multi-shade stump had to be covered with an opaque coping. The use of a translucent glass-ceramic material was contraindicated because a thick layer of ceramic would have been required for masking. As the patient wished, a non-metal restoration, zir conia, was selected. The crown as well as the approximal and occlusal contacts were inspected for fit before cementation. The crown was then degreosed with alcohol.
Fig 15
Figs 16a and 16b
crown.
Frontal and caudal views of the definitive zirconia
Scanning electron micrograph showing the sandblasted surface of the zir conia ceramic. Sandblasting does not enlarge the bond surface area of zirconia ceramics os much os is does that of etched glass-ceramics.
Fig 17
1 06
8.5 Clinical Procedure
Fig 1 8 Cleorfil SE Bond is a two-compo nent bonding system that consists of a self etching primer and on adhesive I bonding ogentl. Both components contain the adhe sive phosphate monomers needed to achieve chemical bonding to zirconia. The primer alone is sufficient for cementation of zirconia ceramics. It acts as a dentin condi tioner and silane activator.
Fig 19 Before cementation, the zirconia ceramic is preconditioned with Clearfil Porcelain Activator, a special silane that must be activated with Clearfil SE Bond primer before application. A mixing dish and a brush ore required.
Fig 20 First, one drop of bond primer is dis pensed into a well of the mixing dish.
Fig 21 One drop of porcelain activator is then added. 107
Chapter 8
Bonding of Ceramic Restorations
1
1
Fig 22 The two liquids form on emulsion like liquid that must be mixed well with a brush.
Fig 23 The mixture should hove a hove a uniform color and consistency.
Fig 24 The activated silane is applied to the inner surface of the crown and allowed to react for 5 seconds. The surplus is then blown off with stream of compressed air
Fig 25 The internal surface of the crown now looks oily. Warning: the external sur face of the crown moy also look oily and feel slippery.
.
Figs 26 and 27 Dentin conditioning primer !ED Primer or Cleorfil) is dispensed into another well of the mixing troy and applied to the prepared tooth with a brush. Priming time: 90 seconds ED Primer/20 seconds Cleorfil SE. Conditioning with silane is recommended when cementing Iorge resin composite build ups. :
108
8.5 Clinical Procedure
Figs 28a and 28b Ponovio 21 TC and Oxyguord; the pastes ore mixed at o ratio of 1 : 1
and applied to the crown with o brush.
Fig 29 Scanning electron micrograph
showing the bond between zirconia !top} and Ponovio lbottoml. The high content of Iorge filler particles in the cement is clearly discernable.
After checking the crown for proper fit, excess cement is removed with foam pel lets.
Fig 30
Oxyguard is applied around the crown margins and allowed to react for 7 minutes. This serves to block the supply of oxygen so that the cement curing process can begin. The Oxyguard is subsequently rinsed off with water, and all cement residues are thoroughly removed with a scaler. Radiological control of fit is possible because the cement is radiopaque.
Fig 31
109
Chapter 8
Bonding of Ceramic Restorations
References l . Albert FE, EI-Mowafy OM. Marginal adaptation and microleakage ofProcera AJ!Ceram crowns with four cements. lot J Prostbodont 2004;17(5):529-535. 2. Anusavice K. Phillips' Science of Dental Materials. Philadelphia: Saunders, 2001 :45 I -486. 3. Bertschinger C, Paul SJ, Uithy H, Scharer P. Dual application of dentin bond ing agents: Effect on bond strength. Am J Dent 1996;9(3):1 15-119. 4. Blatz MB, Sadan A, Martin J, Lang B. In vitro evaluation of shear bond strengths of resin to densely sintered high-purity zirconium oxide ceramic after long-term storage and thermal cycling. J. Prosthet Dent 2004;91(4):356-362. 5. Buithieu H, Nathanson D. Effect of ionomer base on ceramic resistance to fracture. J Dent Res 1993;72:175; Abstract No. 90. 6. Burke FJ, Fleming GJ, Nathanson D, Marquis PM. Are adhesive technologies needed to support ceramics? An assessment of the current evidence. J Adhes Dent 2002;4( 1):7-22. 7. EdelhoffD, Sorensen J. Light transmission through all-ceramic framework and cement combinations. J Dent Res 2002;8 I :Abstract-No I 779. 8. Ferrari M, Mannocci F, Mason PN, Kugel G. In vitro leakage of resin-bonded all-porcelain crowns. J Adhes Dent 1999; I (3):233-242. 9. Gu XH, Kem M. Marginal discrepancies and leakage of all-ceramic crowns: Influence of luting agents and aging conditions. Int J Prostbodont 2003; 16(2): 109-116. l 0. Heffeman MJ, Aquilino SA, Diaz-Amold AM, Haselton DR, Stanford CM, Vargas MA. Relative translucency of six all-ceramic systems. Part I: Core materials. J Prosthet Dent 2002;88:4-9. 1 1 . Jensen ME, Sheth JJ, Tolliver D. Etched-porcelain resin-bonded full-veneer crowns: In vitro fracture resistance. Compend Contin Educ Dent 1989; 10:336-347. I 2. Junge T, Nicholls J, Phillips K, Libman W. Load fatigue of compromised teeth: A comparison of three luting cements. Tnt J Prosthodont 1998; 1 1 :558564. 13. Kappert, H.F. (2003) Klinische Materialkunde fiir Zahniirzte, p. 359. 14. Kern M, Thompson VP. Bonding to glass infiltrated alumina ceramic: Adhe sive methods and their durability. J Prosthet Dent 1995;73:240-249. 15. Magne P, Douglas \VH. Porcelain veneers: Dentin bonding optimization and biomimetic recovery of the crown. lnt J Prosthodont 1999; 12(2): 1 1 1 - 1 2 1 . 16. Malament KA, Socransk.)' SS. Survival of Dicor glass ceramic dental restora tions over 16 years. Part Ill: Effect of luting agent and tooth or tooth-substitute core structure. J Prosthet Dent 200 1;86(5):5 1 1-519. 17. Marquis PM. The influence of cements on tbe mecbanical performance of den tal ceramics. Tn: Proceedings of the 5th lntemational Symposium on Ceramics in Medicine. Bioceramics 1 992;5:3 1 7-324. 18. Paul SJ, Scharer P. The dual bonding technique: A modified method to improve adhesive luting procedures. lnlJ Periodont Rest Dent 1997;17(6): 536-545. 19. Rosenstiel SF, Gupta PK, van der Sluys RA, Zimmerman MH. Strength of a dental glass-ceramic after surface coating. Dent Mater 1993;9(4):274-279.
l l0
References
20. Sjogren G. Marginal and internal fit of four different types of ceramic inlays after luting. An in vitro study. Acta Odontol Scand 1995;53(1 ):24-28. 2 1 . Strub JR, Beschnidt SM. Fracture strength of five different all-ceramic crown systems. Int J Prosthodont 1998; 1 1 :602-609. 22. Tay F, Frankenberger R, Krejci I , Bouillaguet S, Pashley D, Carvalho R, Lai C. Single-bottle adhesives behave as pem1eable membranes after polymerization. In vivo evidence. J Dent 2004;32(8):61 1-621. 23. Van Dijken JW, Hoglund-Aberg C, Olofsson AL. Fired ceramic inlays: A six year follow-up. J Dent 1998;26(3):219-225. 24. White SN, Furuichi R, Kyomen SM. Microleakage through dentin after crown cementation. J Endod 1995;21( 1 ):9-12. 25. Williamson RT, Kovarik RE, Mitchell RJ. Effects of grinding, polishing and overglazing on the flexure strength of a high-leucite feldspatbic porcelain. Jut J Prosthodont 1 996;9( 1 ):30-37.
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Chapter 9
All-ceramic Imp/on/ Supported Restorations
9.1 C l i n ical Aspects a n d I n d ications Natural-looking implant-supported restorations play a major role in the esthetic success of prosthodontic treatments in the anterior region. Two factors crucial to esthetic success are: Soft-tissue morphology Fmm and esthetics of the restoration. •
•
Prefabricated titanium abutments have several esthetic limitations: As their round shape does not correspond to the natural tooth anatomy, the correct contour (emergence profile) must be estab lished by the crown, that is, by deep submucosal placement of the . crown margms. Because the straight shoulder of these standardized abutments does not follow the scalloped contour of the surrounding soft tis sues, the removal of excess cement can be difficult. The gray metallic color of the abutments may show through the soft tissues, resulting in gray discoloration of the gingiva. •
•
•
In order to resolve these problems, individualizable custom abutments made of alumina ceramics were developed in the early 1990s7•8•9• The few available studies on the performance of alumina ceramic abutments show that good long-term results are achieved when these abutments are placed in the anterior and premolar region. In one study, the clinical success rate for alumina ceramic implant abutments was 93% after 1 to 3 years of service2. In a second study, the 5-year success rate for all-ceramic fixed partial dentures supported by alumi na ceramic abutments was 97.2%3. Abutment fracture was identified as the main cause of implant failure in both studies. The introduction of zirconia abutments should reduce the risk of abutment fracture by virtue of their superior material properties. The in vitro fracture load of implant-supported all-ceramic crowns with zirconia abutments was found to be 700 N compared with only 280 N for those with alumina abutments11• Unfortunately, clinical data on zirconia abutments are still scarce. In the only long-term study published to date, none of the zirconia abutments studied had fractured after 4 years of service in the ante1ior 1 14
9.3 Disadvantages
or premolar region'. Based on the available evidence, one can at least conclude that the successful placement of ceramic abutments in the anterior and premolar region is possible.
9.2 Advantages of Cera m ic Abutments •
•
• •
•
Ideal color The white or dentin-like color of ceramic abutments is estheti cally ideal for all-ceramic restorations Gingival recession causes fewer esthetic problems. Customizability The shape of the individualized custom abutment resembles that of a prepared tooth As the emergence profile is determined by the abutment, the crown margins can be scalloped to conform to the architecture of the surrounding soft tissues. Controlled removal ofexcess cement is possible. Correction of implant angulation is possible with some restrictions (minimum layer thickness) The possibility of veneering allows for prosthetic flexibility The implant-abutment connection exhibits good accuracy of fit (due to industrial prefabrication) Radiopacity of the abutment permits radiographic monitoring.
9.3 Disadva nta g es •
• • • •
•
Higher risk of fracture due to the material properties of ceramic materials (see Chapter 2) Minimum layer thicknesses must be observed The screw access hole limits customizability The abutment screw is a the weakest link in the system'0 The dental laboratory procedures are teclmically demanding and time-consuming High cost. 1 15
Chapter 9 All-ceramic Implant Supported Restorations
9.4 Biologic Aspects The morphology of peri-implant soft tissues surrounding titanium abutments is well documented, and clinical parallels to the morph ology of the periodontium have been described4• A soft-tissue collar of given (biologic) width normally forms around a titanium abutment, as around a tooth. This collar of attach ment consists of a layer ofjunctional epithelium (approximately 2 mm) overlying a layer of collagenous connective tissue ( 1.5 to 1 .8 mm). The main morphological difference is that, with abutments, the colla gen fibers run parallel to the implant surface, whereas, in intact teeth, they extend vertically into the root cementum4• Animal studies have shown that the morphology of the peri-tmplant mucosa around alumina and zirconia ceramic abutments is comparable to that around titanium abutments1•6• Ceramic abutments and titanium abutments can, therefore, be classified as biologically equivalent.
9.5 Man ufacturers Because their gray color often leads to gingival discoloration, titanium abutments are frequently unable to meet high esthetic expectations. Consequently, it makes little sense to use metallic abutments as the substructure for all-ceramic restorations. A wide range of ceramic abutments made by various manufacturers is now available for the prosthodontist and dental technician (restorative team) to choose from. The abutment can either be directly veneered (screw-retained) or capped with an all-ceramic crown (cemented). In the latter case, the abutment is prepared as in normal tooth preparation. Generally, most sintered or infiltrated ceramic abutments must be prepared using water-cooled instruments. Selected manufacturers Straumann (Basel, Switzerland): synOcta®. Vita Zahnfabrik: In-Ceram Nobel Biocare: CerAdap� Procera Zirconia and Alumina •
•
1 16
9.5 Manufacturers • • • •
BEGO (Bremen, Germany): Ceramic core materials Friadent (Mannheim, Germany): CERCON Balance Biomet 3i Implant Innovation (Florida, USA): ZiReal®. Wohlwend (Zurich, Switzerland): Zirabut®·
CerAdapt
CerAdapt abutments are made of densely sintered pure alumina and can be combined with Branemark Regular Platform implants (Nobel Bio care) for restorations in the anterior and premolar region. The pre-fabricated cylindrical abutment measures 12 mm in height and 6 mm in diameter. synOcta/ln-Ceram System
The synOcta abutments are manufactured by Straumann, and the ceramic blanks by Vita Zahnfabrik. The ceramic blanks (diameter: 9 mm, height: 1 5 mm) are made of In-Ceram Zirconia. The internal octagon and screw seating of the blanks are pre-infiltrated to ensure optimal fit. The non-infiltrated part of the blank can be easily worked with a grinding wheel. After cus tomized shaping by the dental technician, the blank is infiltrated with a special glass (Vita In-Ceram Zirconia glass powder) to achieve full material strength and hardness. In-Ceram blanks are used for esthetic single-tooth replacements in the anterior and posterior region. The superstructures can be either cemented or screw-retained (case a: screw-retained restoration). Procera Alumina and Zirconia Abutments
Restorations from these two materials can be designed by two methods; the conventional wax-up technique or CAD. With the wax up technique, the abutment design is individually modeled and mechanically scanned. With the CAD teclmique, the abutment is designed on-screen with in an imaginary cylinder measuring 15 mm in diameter and 15 mm in height. Nobel Biocare makes no distinctions with regard to area of indication and their alumina and zirconia abutrnents can be used for both crowns and bridges in the posterior region (case b: cemented sin gle-tooth restoration).
117
Chapter 9
All-ceramic Imp/on/ Supported Restorations
Zirabut
The Zirabut zirconia abutment system developed by Arnold Wohlwend is the system with the longest history of clinical use5• The abutments are designed for use with the Branemark system (WP, RP and NP). The diameter of the abutments ranges from 6 to l O nun depending on which platform is used; all platforms have a height of 14 mm. Any adjustments that may be necessaty are canied out at the dental laboratory using a water-cooled turbine. In cases where the blanks cannot be individualized as desired, a custom-made, copy milled abutment can be ordered directly from the manufacturer (Arnold Wohlwend). Laboratory Procedures
The procedure for fabrication of screw-retained restorations with direct veneering is illustrated in case a (Figs I to 8), and tbat for cemented restorations with an all-ceramic crown is described in case b (Figs 9 to 18).
Case a : Screw-retained restorations
Fig 1
1 18
Wax-up try-in.
9.5 Manufacturers
Figs 2 and 3 A silicone index is fabricated from the diagnostic wax-up and used to gouge the amount of space available for the ceramic.
Fig 4 After customized shaping, the blank is infiltrated with a special gloss Vita lnCer am Zirconia Glass Powder to achieve full material strength and hardness.
5
Fig Creation AV ceramic Uensen Dental Solutions, Connecticut, USA! is used to veneer the ln-Ceram abutment.
Fig 6 Because of the poor thermal conduc tivity of ceramic materials, the piece must be fired on a metal wire support in order to prevent heat build-up.
119
Chapter 9
All-ceramic Implant Supported Restorations
Figs 7 and 8
The final restoration is inserted with a tightening torque of 15 Ncm.
Case b. Cemented single-tooth restorations
Figs 9 and 10
120
Diagnostic wax-up and try-in of the cement-retained restoration.
9.5 Manufacturers
Figs 1 1 to 13 The substructure is over pressed with ceramic pellets to achieve the desired emergence profile.
Fig 14 Shoulder position is verified when trying in the abutment.
Fig 15 Creation AV ceramic is used for . veneenng.
121
Chapter 9
All-ceramic Implant Supported Restorations
Fig 16 The veneered abutment is subse quently etched.
Fig 17 The finished piece is ready for cementation.
Fig 18 One-week follow-up after crown placement.
1 22
References
References 1 . Abrabamsson I, Berglundh T, Glantz PO, Lindbe J. The mucosal attachment at different abutments. An experimental study in dogs. J Clin Periodontol l998; 25(9):721-727. 2. Andersson B, Taylor A, Lang BR, Scheller H, Scharer P, Sorensen JA, Tarnow D. Alumina ceramic implant abutments used for single-tooth replacement: A prospective one- to three-year multicenter study. Int J Prosthodonl 200 I; 14(5):432-438. 3. Andersson, B., Glauser R, Maglione M, Taylor A. Ceramic implant abutments for short-span FPDs: A prospective five-year multicenter study. lnt J Prostho dont 2003; 16(6):640-646. 4. Berglundh T, Lindhe J, Ericsson I, Marinello CP. The soft-tissue barrier at implants and teeth. Clin Oral Implants Res 1991 ;2(2):81-90. 5. Glauser R, Sailer 1, Wohlwend A, Studer S, Schibli M, Scharer P. Experimental zirconia abutments for implant-supported single-tooth restorations in estheti caUy demanding regions: Four-year results of a prospective cliaical study. lnt J Prosthodont 2004; 17(3):285-290. 6. Kohal RJ, Weng D, Biichle M, Strub JR. Loaded custom-made zirconia and titanium implants show similar osseointegration: An animal experiment. J Periodonto1 2004;75(9): 1262-1268 7. Prestipino V, Ingber A. Esthetic high-strength implant abutments. Part. I. J Esthet Dent 1993;5( I ):29-36. 8. Prestipino V, Ingber A. Esthet.ic high-strength implant abutments. Part 11. J Esthet Dent 1993;5(2):63-68. 9. Prestipino V, Ingber A. All-ceramic implant abutments: esthetic indications. J Esthet Dent 1996;8(6):255-262. 10. Tripodakis AP, Strub JR, Kapper! HF, Witkowski S. Strength and mode of fail ure of single implant all-ceramic abutment restorations under static load. Int J Prosthodont 1995;8(3):265-272. I I . Yildirim M, Fischer H, Marx R, Ede.lhoff D. In vivo fracture resistance of implant-supported all-ceramic restorations. J Prosthet Dent 2003; 90(4):325-331.
123
A
c
Abutments alumina 114, 1 1 7 individualizable custom 1 1 4 prefabricated titanium 1 1 4 zirconia 114, 1 16-1 19 AeryIic resin shells 31, 47 Adhesive bonding 94-95, I 0 l Adhesive cements, classification of 96 All-ceramic implants screw-retained 1 1 7-118 cemented 116-117, 120 All-ceramic restorations 82 long-term failure 6 All-ceramic single crowns clinical and laboratory procedure 44 step-by-step procedure 47 Alumina (AI203) 4 At-home bleaching 74
CAD/CAM 5, 14, 18-21, 3�0. 84-85,95 CAM 14 Carbamide peroxide 72-74 Celay system 1 8 Cementation 33 Ceramic powder 14 Ceramics comparison with metals 8 composition and classification 2-5 conditioning of 94, I 00 glass 2-3 glass-infiltrated 2, 4, 82, I 00 high-strength 2, 82-83 optical properties I 0 oxide 2, 4-5 physical properties 6, 8 Choice of ceramic restoration systems 38 Combined bleaching 74 Communication 44 Computer aided design/computer aided manufacturing 5, 14, 18-21, 39-40, 84-85, 95 Computer aided manufacturing 14 Conditioning I 0 I Connector design 86, 88 Copy-milling 14, 18 Crack growth 6, 8 Crystalline particles 2 Crystals 2 Curing agent 96
B Biocompatibility 82 Biscuit bake try-in 33, 54-55 Blanks 4-5, 7 Bleaching at-home bleaching 74 combined bleaching 74 internal bleaching 65 power bleaching 73 Bonding surface area 94 Brittleness 8
125
Index
D
L
Dental hard tissues 2, l 0 Dentin bonding 96,99 conditioning 98-99, 108 Desensitizing agents 99 Diagnostic mock-up 50 Diagnostic wax-up 49-50 Diagnostic work-up 46 Distilled water 14 Ductility 8
Lanthanum glass 4 Laser 19 Layering 14 lithium disilicate 3, 16 Lost wax technique 16, 85
E
Matrix of adhesive cements 96 Metals 8 comparison with ceramics 8 Microleakage 60, 95 Microstructure 7 multi-phase 3-4 single-phase 5 Minimum framework wall thickness 86 Modeling fluid 14, 17 Monoclinic phase 9
Emergence profile l l 4-ll5, 121 Empress" system 16 Etching I 00
F Ferrule effect 61 Fillers 96 Fine hybrid resin composite 35 Fixed partial denture span 82 Flexural strength 6-7 Fracture toughness 6-7, 9 Framework fracture 90-91
G Glass-ceramics 2-3, 6-7 Glass infiltration 14, 1 7 Glassy phase 2-3 Green zirconia 20, 85
H Hydrofluoric acid 34, 101-102 Hydrogen peroxide 65, 72-74
lmpressioning 30 In-Ceram'' system 17-18 Indirect mock-up 3 1 Inorganic fillers 96
126
M Manufacturers 1 1 6 Material strength 38
N
Non-vital teeth 60, 64
0 Occlusal forces 82-83 Opacity 2 Opaque layer 38 Oxide ceramics 2, 4-5
p Peri-implant soft tissues 1 1 6 Phase transformation 9 Phosphate monomers (MDP) 96, 100 Phosphoric acid 34 Posts 61-64, 66, 68 Power bleaching 73 Prefabricated titanium abutments 114 Press furnace (Empress'�) 16 Pressing 14, 16 Procedures CAJD/C� 5, 14, 18-21, 39-40, 84-85,95 lost wax 16, 85
Index
Processing methods 14 Properties of dental ceramics optical properties I0 physical properties 6. 8 Provisionals direct 32 indirect (acrylic resin shells) 31,47 ·
R Radiopacity 86 Resin composite cements 96-98 clinical requirements 98 self curing 97 Retention 94-95 Rocatecr>� system 100
T Tensile stress 8 Tetragonal phase 9 Thermal conductivity 82, 86 Tooth contour 51 Tooth preparation 28, 39, 50, 84 Tooth shape 5 1 Tooth structure loss/preservation 24, 38, 50, 101 Transformation toughening 9 Translucency I 0, 95 of adjacent teeth 38 Treatment wax-up 5 1 ·
u Universal resin cement, dual-curing 97
s Sandblasting 86, 1 0 1 Scanner 85 Sealing agents 99 Selection of ceramic materials 54 Self-curing composite resin 97 Shade selection 52-53 Shoulder preparation 38 Shrinkage 15-17, 1 9 85 Silanes 100, 103, 10 -108 Silanization 34, 101 Silica coating (Rocatec1 system) 100 Sintering 15, l7 Sintering shrinkage 15, 19, 85 Slip casting 14, 17 Space requirements 38, 54 St. Morizer prep set 39-40 Strength of ceramic restorations 7 Stress loading 8 Stump shade 38, 54, 82 Survival rates 39, 42-43, 90
7
v Veneers, cementation of 32, 35
w Wax frame 85 Wax-up 27, 33 diagnostic 49 treatment 51 White light scanner 19 Whitening strips 78
z Zirconia (Zr02) 4-5,9-10, 19-2 1 , 4 1 , 63-64, 66, 83, 85-91, 101, 106-107, 109, 1 14, 1 16- 1 1 9 abutments 114, 1 1 6 - 1 1 9 posts 63�4, 66, 68 yttrium-stabilized 82
127