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...... eram1cs Christoph Hammerle Irena Sailer Andrea Thoma Gianni Halg Ana Suter Christian Ramel
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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
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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
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1.1
Scientific Aspects of Dental Ceramic Materials..... 1 Composition and Classification of Dental Ceramics
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1.2 Physical Properties ......................................................... 6 1.3 Opt ical Properties ........................................................ 10
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Processing Methods
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2.1 Manual Processing Methods .................................... 14 2.2 Machining ...................................................................... 18
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Veneers .. ... .... . .... ........ ... .... ............. .
3.1 Indications
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3.2 Contraindications
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3.3 Clinical Guidelines ..... ... .... .... ......... .. ... .... .. . .... 25 .
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3.4 Step-by-step: Clinical Procedures for the Fobrication of Veneers
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All-ceramic Single Crowns .. ........... . ..... .... .. . ... 37 ..
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4.1 Indications ...................................................................... 38 4.2 Tooth Preparation ........................................................ 39 4.3 Clinical Survival ............................................................ 40 4.4 Clinical and Laboratory Procedures ...................... 44
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Non-vital Abutment Teeth ............................... ......... 59 .
5.1 Biomechanics of Non-vital Teeth ............................ 60
5.2 Posts
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5.3 Esthetics ........................................................................... 64 5.4 Clinical Procedures ..................................................... 67
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External Bleaching........................................................ 71
6.1 Introduction ..
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6.3 Combined Bleaching .................................................. 74 6.4 At-home Bleaching . ... .... ........ ......... ........ ............. 74 .
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6.5 "Over-the-counter" Teeth Whit ening Products ...... 78 VII
Contents
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7.1
All-ceramic Fixed Partial Dentures .. General Considerations
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7.2 Indications ...................................................................... 82 7.3 Tooth
Preparation ........................................................ 84
7.4 Dental Laboratory and Dental Office
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Clinical Survival
7.6 Conclusions
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Rates ................................................ 90
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Bonding of Ceramic Restorations . ..
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8.1 Adhesive versus Conventional Cementation ...... 94
8.2 Classification of Adhesive Cements . 8.3 Dentin
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Conditioning ....................................................
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8.4 Ceramic Conditioning .............................................. 100
8.5 Clinical Procedures . .
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All-ceramic Implant Supported Restorations...... 113
9.1 Clinical Aspects and Indications ........................... 114 9.2 Advantages of Ceramic
Abutments......................
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9.3 Disadvantages ............................................................ 115 9.4 Biologic Aspects .. ..
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Manufacturers .............................................................
10 Index
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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. •
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• •
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. •
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1.1
1.1.1
Compos ition and Classification of Dental Ceramics
Main Chara cteristics
Glass-ceramics •
• •
•
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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 •
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•
•
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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 • •
•
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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 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
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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. .
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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.
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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
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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 • • • •
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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 •
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• •
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.
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Schematic diag ra m of tooth preparation.
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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
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3.4
Step by step Clinical Procedure for the Fabrication of Veneers -
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:
Diagnostic procedure
The desired restoration was modeled 1n wax.
Fig 4
A silicone impression of the additive wax-up was then taken.
Fig 5
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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 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
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
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58
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c: (])
.�
::l ....0
-
