Kenneth A. Malanient, DDS, MScD* Tufts LJniversity Boston, Massachusetts

Nicola Pietrobon, CDT** The Interdisciplinary University of Zurich Relationship Between Zurich, Switzerland Prosthodontics and Stephan Neeser, CDT Inprotek Dental Laboratory Dental Technology Boston, Massachusetts

Prosthodontists are often unaware of difficulties faced by dental technicians. Likewise, dental technicians may be unaware of difficulties faced by prosthodontists. By being better educated about one another's discipline, prosthodontists and technicians can establish cooperative goals and help each other to identify significant facts and potential difficulties posed by specific materials, techniques, or stages of the work in progress. This article describes specific procedures for prosthesis fabrication and the opportunities each step provides for such cooperation. The steps include diagnostic waxing, provisional restoration, fabrication of master dies, tooth preparation, fabrication of intraoral records, treatment waxing, selection of materials, use of ceramic mucosal simulations, and color selection. If the prosthodontist and dental technician are willing to share responsibility for treatment plans, their mutual understanding can bring new insight to old problems and provide intellectual stimulation to both. Int] Prosthodont W96;9:341~354.

ver the last decade dental technology, dental education in each discipline fails to support this in- Oscience, and dental practice have advanced teraction; in practice, communications break dramatically, greatly expanding and improving the down, and practical problems result. choices of materials and techniques. The most im- Cooperative goals must be established and better portant issues in today are not about ways to share knowledge must be found. When which material, color, or technique is best. The prosthodontists and technicians each understand most significant issues are interpersonal. In spite of the many variables and problems the other faces, the potential for a unique collaboration between they can work as a team, helping one another to the prosthodontist and the dental technician. identify significant facts and potential difficulties posed by specific dental materials, techniques, or stages of the work in progress. In this way both dis- 'Lecturer, Post-Craduate Prosthodontics and Periodontics; ciplines share responsibility for treatment plans Private Practice, Boston, Massachusetts. based on mutual understanding. An appreciation **Head of Dental Technology, Department of Prosthodontics. of the objectives and responsibilities of each disci- pline ultimately helps the individual to advance in- Reprint Requests: Dr Kenneth A. Malament, 50 Staniford Street, Boston, Massachusetts 02114. dividual professional goals. This article outlines the steps in prosthesis fabri- Presented by Mr Pietrobon at the International Society of cation and emphasizes areas of difficulty for the Dental Ceramics, Young Speaker of the Year Competition, prosthodontist of which the technician might not be lOth Internationa! Symposium on Ceramics, New Orleans, aware, as well as areas of difficulty for the techni- Louisiana, 31 May-2 ¡une 1991; and at the Northeastern Gnathological Society Meeting, New York, New York, 17 cian of which the prosthodontist might not be April 1992. aware. Opportunities for cooperation are described.

Volume 9, Number 4, 1996 341 The International Journal of Prosthodontics Prosthodontics and Dentai Technoiogy Maiament et al

Responsibilities of Technicians and Preston and Bergen^ have established requirements Prosthodontists and discussed factors involved with tooth color. Stein" described the esthetic appearance of teeth as The mandate and responsibility of the prosthodon- controlled more by form and the emergence profile tist is to restore patients' oral function to improve than by color. the health, comfort, and appearance. The There are many steps in building a successful contributes to the general practice of dentistry by prosthesis, and the temptation to combine or omit providing expertise in diagnosis, treatment plan- steps should be resisted. ning, and proper care sequencing. The American Dental Association's Standards for Advanced Diagnostic Waxing Specialty Education Programs in Prosthodontics call for an in-depth knowledge and clinical com- An accurately mounted diagnostic cast is prepared petency in fixed, removable, implant, and maxillo- to resemble the planned tooth preparations. The facial prosthodontics. diagnostic waxing, made on this cast, reestablishes Laboratory procedures that must be mastered by proper arch form, occlusal plane and form, tooth the technician (and understood by the prosthodon- contours, and esthetics. It can be used as a blue- tist) are diagnostic waxing, provisional restoration, print for both the provisional and definitive restora- master dies, framework or core fabrication, tion.-'' Computer imaging is helpful in initially di- fabrication, and . recting thought regarding the patient's esthetic The dental technician supports the prosthodontist's desires in planning the diagnostic waxing. The effort in many ways. Indeed, dental technicians have waxing procedure, however, defines three-dimen- made major contributions to dental materials sci- sional problems that both the prosthodontist and ence. A standard for excellence in dental ceramics technician will encounter and must resolve. was established by Dicor glass-ceramic (Dentsply Furthermore, the diagnostic waxing can be helpful International, York, PA), which was researched and as a teaching model. The patient can understand developed by Peter Adair and Dr David Grossman at problems better by seeing them and discussing Gorning Glass Works; Empress glass-ceramic them with the prosthodontist. This information can (Ivoclar, Schaan, Liechtenstein) was researched by be shared with the technician, and needed alter- Arnold Wohiwend at the University of Zurich, ations can be easily made. Zurich, Switzerland; Creation iridescent feidspathic porcelain Oensen, North Haven, CT) was researched Provisional Restorations by Willi Geller; Vintage/Opal feidspathic ceramic (3M-Unitek, Monrovia, CA) was researched by Ideally, a provisional acrylic resin restoration Makoto Yamamoto; and Omega and Alpha opales- should be flasked and heat processed. The diag- cent feidspathic ceramic (Vita, Bad Säckingen, nostic waxing can provide the form for the resin Germany) was researched by Claude Sieber. The teeth. The technician can make the provisional Alpha ceramic greatiy improved the color properties restoration in acrylic resin alone, or the resin may of Vita's In-Ceram glass-ceramic, which had been be supported by a metal framework. The prostho- developed by Dr Michael Sadoun, a . These dontist should let the technician know that an all- and other ceramic materials, equipment, and new resin restoration can be more convenient, espe- forming techniques have improved the marginal fit cially when it replaces an existing prosthesis and and optical properties of dental prostheses and have substantially affected dental practice. when the underlying form of the tooth preparation is not known. If the prosthodontist needs to create additional space in the provisional restoration, the Cooperation in Developing a task will be more difficult and frustrating if a metal framework, as well as the resin, must be reduced. Cooperation between prosthodontists and dental An all-acrylic resin prosthesis is usually preferred technicians rests on a mutual appreciation of the following initial tooth preparation. anatomic deficiencies that limit the esthetic result A long-term provisional restoration is ideal for in prosthodontics. In describing the esthetic factors patients who have long edentulous spans or who related to teeth. Miller^ noted that teeth have both will be undergoing extensive periodontal surgery three-dimensional (form) and two-dimensional (sil- and will require substantial time for healing.^ An houette) visual properties. The nature of the gingi- impression of the tooth preparations is made, and val framing or dark spaces around teeth affects the casts are accurately mounted on an articulator. their symmetry. Although Stein and Kuwata^ and A metal framework is cast to fit the dies, which

The Internationai Jotirnai of Prosthodontics 342 Voiurtie 9, Number 4, 1996 MalamenI el al Piosthodonlics and Oenlal Technology

have been given additional die-spacing material, and the margin areas are waxed short of the finish- ing line. Accuracy is unnecessary at this stage be- cause the margin will be established in acrylic resin after the relining process. Acrylic resin teeth can be used or the teeth can be manually waxed, and the finished waxed margins can be established on this metal and stone cast. The stone cast, metal frame- work, and wax or resin are embedded in stone and flasked for acrylic resin processing. Alternatively, the technician can completely wax the forms, flask, eliminate the wax, and pack complete acrylic resin forms on the metal framework. The metal frame- work in this type of provisional prosthesis makes it Fig 1 Complete stioulder tooth preparations. relatively fracture resistant.

Master Dies resistance form, and finish line design as the physi- The new generation of poly(vinyl siloxane) or poly- cal factors crucial to a long-lasting prosthesis. Even ether impression materials produces highly accu- with the recent improvements in dentin bonding rate, stable dental impressions that can be poured materials and luting agents, proper attention to many times to produce accurate stone tooth preparation cannot be ignored. Many authors casts.'i"^-"*' It is helpful if the prosthodontist uses have described the merits of different margin de- these newer, more stable impression materials that signs. Shoulder or chamfer preparations have been do not require immediate pouring, and therefore advocated for use with all-ceramic materials.'" do not force technicians to interrupt sensitive pro- Friedlander et al""'^ and Bernal et al'"' have shown cedures or disturb their concentration. that shoulder preparation (Fig 1 ), with its buttressing Previous die systems used plaster bases and were qualities, produces strong all-ceramic crowns that more likely to distort because of the unpredictable resist fracture forces better than crowns with cham- expansion properties of setting gypsum. Newer mas- fer margins. Stein and Kuwata,^ McLean,'^ ter die systems, such as the Zeiser^ (Zeiser, Girrbach Preston,'^ and Miller" have advocated proper Dental, Santa Rosa, CA) and Kiefer Systems (Vita), tooth reduction for dental ceramics. All authors use indexed resin bases that have improved die po- have suggested a minimal reduction of 1.4 mm for any type ofdental ceramic. Ample reduction allows sition accuracy and stability."™"'"' Such die sys- the technician to make a strong ceramic restoration tems allow greater accuracy of the die-master cast with good color developed by layering or stratifica- relationship following sectioning. The demand for tion methods. Miller" has demonstrated that at these types of systems is increasing as more least 0.7 mm of ceramic veneer is needed for the attempt to complete restorations without trial place- development of correct tooth color. ment procedures. These systems are also popular with dentists who use all-ceramic materials for fixed When preparing teeth, the prosthodontist may partial ; all-ceramic prostheses must be have to deal with poor visibility, poor preparation made in one piece because they cannot be sol- anatomy, or awkward handpiece control. These dered. Unfortunately, many variables, including the problems can affect tooth preparation form and dimensional changes of the impression material or margin definition. When a shoulder finishing line setting stone, still have the potential to distort the is improperly finished, unsupported or "lipped" positional accuracy of a sectioned master areas may result.'^ Such compromised finishing C25t 7(77-87,89-103) -p^al placement procedures should line forms are a source of frustration for dental not be omitted until further improvements are made technicians. It is difficult to make an accurate im- pression of a lip on a margin area, and the result- in pin and individual die stability. ing casts are often distorted. The technician has difficulty defining or scribing poorly defined finish- Tooth Preparation ing lines. Waxing procedures are difficult, and the pattern is often distorted during removal from the A strong, well-fitting, and esthetically pleasing den- die. It is difficult to accurately fit the resultant cast- tal restoration absolutely requires proper tooth ings without harming the die. These difficulties can preparation. Black' established length, width, taper.

"-'•ime 9, Number 4, 1996 343 The international Journal of Prosthodontics Prosthodontics and Dental Technology Maiament et al

Fig 2 Implant impression copings placed for fabrication of Fig 3 Anterior composife resin jig made af the desired verfi- the masfer casf. cal dimension of occlusion and used fo record cenfric reiafion.

making rims that can be positioned on teeth or im- pianfs wifh cenfrai bearing poinf piafes to assist fhese procedures," Bofh of these laboratory de- vices heip fhe prosthodontist fo make accurate records af a desired vertical dimen- sion, A panfographic record may be used fo record excursive mandibular movemenfs,^" If an elec- fronic pantograph is unavailable, the dental techni- cian can mount fhe record clutches and panto- graph on a completely adjusfable articulator. Working togefher, fhe prosthodontist and fechni- cian can set the arficulafor using the pantographic fracings. Casts can be mounted on the articulator Fig 4 Mefal ceramic impiant prosfhesis wifh gihgiva-colored wifh fhe facebow and cenfric reiafion records. feldspafhic porcelain. Treatment Waxing

This simple procedure, whiie adding exfra cosf and time, produces considerable benefits because it ulfimately result in a completed restoration thaf is substantially improves the understanding, commu- eifher foo loose, or that fits so fightly that pressures nication, and collaboration between fhe prosfho- created during luting fracture a ceramic margin. donfisf, denfal technician, and patient,^ It is a triai Even when the greatest care is faken, a problem placemenf waxing, made from toofh- and gingiva- usually compromises ideal margin form. Hand in- colored wax (Chroma Wax, Benzer Denfal, Zurich, struments or tissue-safe end-cuffing shoulder burs Switzerland) (Figs 5 and 6) that allows ali parties to are helpful in properly flaftening fhe toofh prepara- preview fhe esthetic resuit anticipated for the defini- fion and preventing and reducing fhe pofenfiai for tive prosthesis. The wax should be tooth-colored,^' the formafion of a iip, because a patient cannot easily relate to colored wax teeth. The frial waxing is complefed on the Intraoral Records master dies and can be tried in fhe moufh and used to tesf fhe confour and shape of the most simple an- Intraoral records may include centric relation terior unit or a complex complete rehabilitation. In records, facebow recordings (mean value or kine- edenfulous pafienfs whose treatment involves com- matic), or panfographic fracings. The fechnician plete implanf prosfhodonfics, arfificial feeth can be can collaborafe by making centric reiafion guides arranged on a frial denfure base (Figs 7 fo 10), This (Figs 2 fo 4) at an arbitrary verticai dimension, and is developed fo meet the patient's individual

The International lournal of Prosthodontic 344 Volume 9, Number 4, 1996 and Dentai Technoiogy

Fig 5 Intraorai triai of anterior treatment-wax forms. These Fig 6 Anterior Empress ail-ceramic restorations made from can be adjusted to correct esthetic deficiencies. treatment-wax forms.

Fig 7 Artificiai teeth arranged on a triai denture base to Fig 8 The wax treatment denture converted to treatment meet the patient's individuai esthetic and tunctionai needs. waxing connected to the impiants.

Fig 9 Metal ceramic implant framework designed to support Fig 10 Metal ceramic maxillary implant prosthesis. both tooth- and gingiva-coiored porceiain.

9. Number 4, 1996 345 The Internationai Journai of Prosthodontics Prostbodontics and Dental Technology

Fig 11 Worn composite resin restoration repairing a frac- Fig 12 Metal ceramic 36O.degree collarless teldspathic tured tooth. porcelain complete-coverage restoration.

esthetic and functional needs. The wax treatment Chroma Wax, developed by Wohlwend, and denture can then be converted to an accurate im- other tooth-colored waxes can be highly accurate plant treatment waxing. Getting the patient's ideas and burn out properly. These complete-contour about appearance during the treatment waxing wax teeth can be reproduced in gold alloy, glass- stage can be most helpful and can reveal errors in ceramic, or press-formed ceramic. tooth or pontic piacement. Although computer imaging is useful for providing alternative working Selection of Dental Materials plans quickly, it does not provide as much real pa- tient information as does the treatment waxing. Materials for fixed prostheses continue to improve Often the computer image does not reflect prob- in strength, marginal accuracy, and color. lems that are apparent on the master cast or in the Although ceramic materials are the most estheti- mouth. Digitai images present a two-dimensional cally pleasing, debate continues as to whether all- illusion that cannot be touched or seen directly in ceramic or metal ceramic materials are prefer- the patient's mouth, whereas a technician or able.^''"^^ The answer lies in the education and prosthodontist can directly alter the treatment wax- talent of individual dental technicians and prostho- ing to develop optimal form and contour. Even with dontists, and in the treatment plans upon which the diagnostic waxing and casts of the provisional they agree. Color communication, tooth form, restorations, large discrepancies may exist between opacity, translucency, fit, and biocompatibility the first treatment waxing and the patient's esthetic must all be addressed. Currently, all-ceramic mate- desires. The treatment waxing may be easily al- rials are useful only as individual restorations, al- tered. An impression may be made of the accepted though some have potential as short-span can- complete contour waxing to make an index. This tilever or three-unit anterior fixed partial tooth contour guide form allows the technician to dentures.^^"^' Metal ceramic restorations continue fabricate restorations having optimal strength, accu- to be the state of the art.^^'^'*''"'''" They are the most rate occlusion, and the desired optical properties. versatile materials and can be used in any situa- The dentist's common practice of viewing ceramic tion, as a single-unit restoration or within the most restorations just prior to glazing can lead to prob- complex complete fixed or implant prosthesis, pro- lems if major alterations are needed. After large al- vided there is sufficient space to ensure that the terations, the ceramic material may no longer be prosthesis will have the necessary strength to with- properly supported by the metal framework. stand oral forces. Furthermore, if the dentist grossly alters contours in The prosthodontist must be aware of advances in the preglaze phase, color effects may be perma- metal ceramic techniques. The color properties of nently lost. Ceramic color is best developed by metal ceramic restorations can be competitive with stratifying different opaque and translucent porce- all-ceramic restorations (Figs 4 and 9 to 18). The lains, and technicians spend much time developing technique of ceramic stratification,' described by these subtle but essential effects.'^'^^"^'' Geller and Wohlwend (unpublished data),

The International )ournal ot Prostbodoi 346 Volume 9, Number 4, 1996 Prosthoclontits and Dental Technology

Fig 13 This patient required a complete reconstruction be- Fig 14 Maxillary metal ceramic reconstruction for fixed par- cause of worn restorations, periodontal disease, and caries. tial dentures and the need to splint teeth to limit toofh mobility. The mandibular reconstruction was fabricated as individual In- Ceram all-ceramic restorations.

Fig 15 Completed reconstruction. Note the similar appear- Fig 16 This patient required anterior restorations to correct ance of the In-Ceram and metal ceramic restorations. The In- existing esthetic deficiencies. Ceram copings were veneered with feldspafhic porcelain.

Fig 17 New anterior ceramic restorations. Note that it is dif- ficult to know which restoration is fabricated from metal ce- ramic or Dicor all-ceramic materials.

Fig 18 Marginal and occlusal view of the new restorations. There is a metal ceramic fixed partial denture and individual Dicor complete coverage restorations.

Volume 9, Number 4, 1996 347 The International journal of Prosthodontics Prosfhodontics and Dental Technology

Fig 19 Inadequate dentistry with poorly adapted margins Fig 20 The completed reconstruction using Empress all-ce- and decay necessitated a complete reconstruction. ramic anterior restorations to the premolars and Ih-Ceram all- ceramic posterior restorations.

McLean,''^ and Sieber,"*^ has significantly enhanced strong as metal ceramic restorations.'^'^^''^'"-" As ceramic fabrication. The use of computer-controlled the more desirable strength of ceramics is im- ceramic furnaces and improved insulation has made proved, so is its inherent opacity. The color proper- ceramic processing more predictable."""™ Another ties of all glass-ceramic maferials require veneering advance is in the more stable, accurate, and translu- with feldspathic porcelain layers (Figs 21 and cent color properties of shoulder porcelain.^'"^' 22)." Color may be easiest to develop over a Opalescent feldspathic ceramic materials such as glass-ceramic core,'* particularly because of the Omega, Creation, or Vintage possess an important continuing improvements in the quality of the dif- color quality of natural teeth previously lacking in ferent veneering porcelains and infusion glasses metal ceramic restorations. (In-Ceram, Vident). Wear continues to be a factor Nonetheless, the visibility of the metal frame- with feldspathic porcelain because it is more abra- work necessitates the addition of an opaque porce- sive than tooth enamel.'™"'"^ Although the Dicor lain layer that interferes with the ideal optical ef- material appears to be less abrasive to tooth fect of metal ceramics. This requirement has enamel, most clinical conditions require veneering nurtured interest in all-ceramic materials that could Dicor with feldspathic porcelain. With the contin- eliminate the metal framework entirely. Although ued development of dentin bonding, ceramic acid- all-ceramic crowns have been in use for the past etching, silanation, and resin luting, the fracture century, the porcelain jacket was the first generally rafes of all-ceramic materials are decreasing sub- accepted all-ceramic material.^^"^^ As the science stantially.'''''"'"'^^ Thus, the continuation of re- of dental ceramics improved, materials such as search, development, and use of these materials is Cerestore (Coors Ceramic, Colorado),^^ Dicor assured. (Dentsply)''''-'''' (Figs 17 and 18), Cerapearl (Kyocera Bioceram Group, Kyoto, Japan),™''' In- Ceramic Oral Mucosa Simulation Ceram (Vident, Baldwin Park, CA)"-™ (Figs 14 and 15), and Fmpress (Ivoclar North America, Amherst, Gingiva-colored ceramics have been developed |sjY)8i-85 (pjg5 5^ 19^ and 20) were developed. sufficiently so that they are now suitable for either These materials are organized crystalline forms, tooth- or implant-supported fixed prosthodon- unlike feldspathic dental porcelain. Improved ma- (¡(,5123-125 ji^gy 3|.g ujgj (Q recreate normal mu- terials for feldspathic-based porcelain have been cosal contour and are particularly effective in flat, developed and include Renaissance (Williams, edentulous areas or in areas with residual ridge de- Amherst, NY),•">•"' Captec (Leach and Dillon, fects (Figs 2, 4, 10, 23, and 24). They also can im- North Attleboro, MA), and magnesia ceramic.ä^"'" prove tooth-gingiva symmetry or correct gingival Glass-ceramic materiais are significantly stronger defects that cannot be repaired surgically. Finally, than dental feldspathic porcelain, but are not as they can provide lip support for patients with im-

The international Journal of Prosfhodonfics 348 Volume 9, Numher 4, 1996 ProsthodontJcs and Dental Technology

Fig 21 Maxiilary leff compiefe coverage restorafion (Dicor), Fig 22 A new maxillary leff compiefe coverage restoration Nofe thaf the color is low value and perceived by the pafient (Dicor), Note fhat fhe color is more pleasing because a Dicor as "gray," Three surface coloring procedures were made on coping veneered wifh feldspafhic porcelain provided greater fhe compiefe confour casfing. depth of color and opacify.

Fig 23 Mefal ceramic framework designed fo supporf footh- Fig 24 Denfal and gingival feldspafhic porcelain fixed partial and gingiva-colored feldspathic porcelain. The framework is denture thaf replaces missing feefh and compensates a large designed fo allow small spaces and gingival embrasures be- residual ridge defecf. fween ceramic gingiva and feefh.

plants, and offer the advantage of being easy to differenf color properties. Opaque and translucent clean. Development and improvements in differenf areas in feeth, and even fhe size, shape, and color gingiva-colored porcelains are continuing. of fhe gingivai frame, are important facfors fhaf musf be described before an individuai foofh coior can be developed,'-3'"Ä24,40,i28 Selection of Color Toofh shade decisions are difficult,'^'-'" In the Clark,""- Sproull,'" and Preston and Bergen^ de- end, fhe communication between the prosthodon- scribe tooth color as a function of hue, chroma, and tist and the technician is based on estimation modi- vaiue. Factors thaf influence fhe absorpfion and re- fied by numerous facfors involving training, experi- flection of light (opacify, franslucency, opalescence, ence, environment, and acuify of percepfion. iridescence, and phosphorescence) are of major im- Ideally, color should be described before any freaf- portance. An individual's physical abiiify to per- ment by the dentist is inifiafed, Riley and ceive and interpret light data is essentiai to describ- Filipancic"' have shown fhaf teeth dry out when ing coior. The different areas of a footh have fhe mouth is open during denfai freafment, and

""'••ne 9, Number 4, 1996 349 The Internationai Journal of Prosthodontics Prosthoclonlics 3nd Denial Technology Malament et

Fig 25 Dicor castings made trom a custom shade tab mold. Fig 26 Custom coior tab has been made and examined in Feldspathic porceiain is appiied to ttiese tabs to deveiop indi- the patient's mouth. The tab ooior can be shown to the patient viduai color records tor anterior restorations. The tab castings for a reaction. The tab can be photographed compared to the are made in the actuai coping materiai that wiii iater be used. naturai teeth, restorations, or commerciai shade tabs. This This estabiishes a more accurate record and better taciiitates photograph is a record that can be sent to a iaboratory techni- communication and understanding between prosthodontist cian to highiight deficiencies requiring correction. and laboratory technician.

such desiccation significantly changes the tooth Conclusion coior. The environment also influences shade deci- sions, since fhe time of day and variations in artifi- Dental technology and prosthodontics create an es- cial light can affecf shade recordings. Miller' has thetic illusion whiie providing function and health. demonstrated that present dental shade guides do Preston (personal communication) notes that it is not represent the range of color in respect to hue, important to understand which elements of a pros- chroma, or value found in natural teeth. Further- thesis are illusion and which are reality. Nothing is more, the poor quality control of dental shade perfect; indeed, an obsession with creating the per- guides results in inconsistent, often inaccurate, fect illusion of a natural tooth can confuse our main color information. Most are not made of dental ce- responsibility, which is the patient's long-term ramics, but may be made of either acrylic resin or heaith. The challenge of prosthodontics is to main- layered high-fusing quartz-based ceramic.^-'^^ tain the highest standard of patient care. Finally, commercial shade guides are generally 3.5 The problem defined as the difference between mm thick, and are thus inconsistent with the results what we have and what we want, can be analyzed of actual veneering proceduresJ'^-"''"' and solved in different ways. Systems anaiysis offers Given the limitations on the prosthodontist's three approaches: First, more information or better ability to determine the proper color of teeth, it is methods for analyzing existing information may be helpful to involve the patient directly in color deci- needed. Unfortunately, the information prosthodon- sions, and it is essential to involve the fabricating tists and technicians rely on is often oversimplified technician. Riley and Filipancic"' have described or overstated, since it frequently comes from the use of custom-made shade tabs to facilitate sources that have a proprietary interest in a particu- color selection and development. A metal wax pat- lar material or technique. Second, all the avaiiabie tern former can be made to cast or form custom information may be present, but, because develop- shade cores in metal or glass ceramic (Figs 25 and ments in dental science, materials, and techniques 26). Feldspathic porcelain can then be layered on continually change the way dentistry is provided, the cast core to develop the correct tooth color. A new insight into the nature of the problem may be custom-fabricated shade tab more correctly repre- needed. At the same time, change must be ap- sents the required color because the individual proached with caution, since commerciai ciaims core qualities to be used in the prosthesis are rep- often exceed actual ciinicai performance. Dental resented. The creation of custom color tabs also technicians and prosthodontists should not tai

The Internationai Journal of Prosthodontic 350 Voiume 9. Number 4, t996 Ptosthodontics and Dental Technology

and experience, produces the highest standards of 10. Sorensen |A, Torres Tj, Kang SK, Avera SP. Marginal fidelity of treatment. Within this conservative, educated ap- ceramic crowns with different margin designs labstract 1365|. proach there is still much room for artistic expres- I Dent Res 1990:69:279. 11. Friedlander LD, Munoz CA, Coodacre C|, Doyle MC, Moore sion and advancement of both new technologies BK. The effect of tooth preparation on the breaking strength of and the standard or care. As Einstein said, "It's the Dicor crowns: Part 1. Int I Prosthodont 199O;3:1S9-168. ideal that animates our best actions."'^*' 12. Friedlander tD, Munoz CA, Coodacre C), Doyle MG, Moore Third, we may need to look at ourselves and ex- BK. The effect of footh preparation on the breaking strength of amine whether we are too intellectually comfort- Dicor crowns: Part 2. Int) Prosthodont 1990;3:241-248. 13. Friedlander LD, Munoz CA, Goodacre CJ, Doyle MG, Moore able with the convenient, familiar standard of BK. The effect of tooth preparation on the breaking strength of knowledge that we possess. Complacency can Dicor crowns: Part 3. Int I Prosthodont 1990;3:327-340. block understanding and the ability to work with 14. Bernai G, Iones RM, Brown DT, Munoz CA, Goodacre CJ. better solutions. The effect of finish line form and on the breakage Collaboration between dental technology and strength of Dicor crowns. Int 1 Ptosthodont 1993;6:286-29ü. 15. McLean |W (ed). The Nature of Dental Ceramics, monograph prosthodontics fosters an exchange of information, 1, The Science and Art of Dental Ceramics, vol I. Chicago: creates opportunities for new insight into the effects Quintessence, 1979:23-51. of recent developments, and provides the impetus 16. Preston ID. Rational approach to tooth preparations for cetamo. to improve our standard of knowledge. It results in metal restorations. Dent Clin North Am 1977,21:683-698. the continuous refinement of treatments and the de- 17. Miller LL. A clinician's interpretation of tooth preparation and the design of metal substructures for metal ceramic restora. velopment of new definitions for clinical practice. tions. In: McLean ]W (ed). Dental Ceramics—Proceedings of Thus, the scarcity of education and training pro- the First International Symposium on Ceramics. Chicago: grams for dental technicians poses a serious prob- Quintessence, 1983:153-206. lem. If prosthodontics and dentistry are to continue 18. Malamenf KA. Considerations on posterior glass.ceramic to mature, more attention must be paid to, and op- restorations. Int) Petiodont Rest Dent 1988;8(4):33-50. 19. Rieder CE. The use of provisional restorations to develop and portunities created for, collaboration with dental achieve esthetic expectations. Int ) Periodont Rest Dent 1989: technology. To truly understand the problems we 9:123-139. face, prosthodontists and dental technicians must 20. Guichet NF. Principles of Occlusion. Anaheim, CA: Denat, listen to and work closely with each other. 1970:37-66. 21. Roge M, Preston )D. Color, light and the perception of fotm. Quintessence Int 1987;18:391-396. Acknowledgment 22. Yamamoto M. Metal ceramics. Chicago: Quintessence, 1985:268^02. The authors would like to thank the members of the Department 23. Kedge M. Lateral segmental build.up. In: Preston )D (ed). of Prosthodontics at fhe University of Zurich for their contribu- Perspectives in Dental Ceramics—Proceedings of the Fourth tions to this article. International Symposium on Ceramics. Chicago: Quin. tessence, 1988:369-374. 24. McLean JW, leansonne EE, Chiche G, Pinault A. AlUceramic References crowns and foil crowns. In: Chiche CJ, Pinault A (eds). Esthetics of Anferior . Chicago: Quin- 1. Miller LL. Scientific approach to shade matching. In: Preston tessence, 1994:75-111. )D (ed). Perspectives in Dental Ceramics—The Proceedings of 25. Campbell SD. A comparative strength study of metal ceramic the Fourth International Symposium on Dental Ceramics. and ail.ceramic esthetic materials: Modulus of rupture. J Chicago: Quintessence, 1988:193-208. Prosthet Dent 1989;62(4):476-479. 2. Stein RS, Kuwata M. A dentist and a dental technologist ana- 26. Sorenson )A, Qkamoto SK. Comparison of marginal fif of all- lyze current ceramo-metai procedures. Dent Clin North Am cetamic systems [abstract 1415]. J Dent Res 1987: 1977;21:729-749. 66:283. 3. Preston |D, Bergen S. Color Science and Dental Art. St touis, 27. Scharer P, Sato T, Wohlwend A. A comparison fit of the mar. MO:Mosby, 1980:1-76. ginal fit of three cast ceramic systems. J Prosthet Dent 1988: 4. Stein RS. Periodontal dictates for esthetic ceramometal 59:534-542. crowns. ) Am Dent Assoc 1987;115:63E-73E. 28. Wohlwend A, Strub JR, Scharer P. Metal ceramic and all. 5. Tarantola C), Becker IM. Definitive diagnostic waxing with porcelain restorations: Current considerations. Int J light-cured composite resin. I Prosthet Dent 1993,70:315-319. Ptosthodont 19a9;2:13-26. 6. Nevins M, Skutow HM. The intracrevicular restorative mar- 29. Seghi RR, Sorensen JA, Engelman MJ, Roumamas E, Torres DJ. gin, the biologic width, and the maintenance of the gingival Flexutal strength of new ceramic maferials [absfract 1521]. J margin. Int) Periodont Rest Dent 1984:4(3):31-S0. Dent Res 1990:69:299. 7. O'Brien WÍ. Dental Materials—Properties and Selection. 30. Drummond JL, Novickas D, Lenke JW. Physiological aging of Chicago: Quintessence, 1989:77-87,89-103,192-194. an all.ceramic restorative material. Dent Mater 1991:7: 8. Zeiser M. ModelUSystem mit kunststoff.sockelplatte ¡etz auch 133-137. fur kleine labors. Dent tah 1982;30:489-490. 31. Scherrer SS, de Rijk WG. The fracture resistance of all. 9. Black GV. Operative Dentistry, ed 8. Woodstock, IL: Medico. ceramic crowns on supporting structures with different elastic Dental, 1947. moduli. Int) Prosthcdonf 1993:6:462-467.

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32. Campbell SD, Kelly JR. The influence of surface preparation 55. Chaffee NR, Lund PS, Aquilino SA, Diaz-Arnold AM. on the strength and surface mieroslrueture of a east dental ee- Marginal adaptation of porcelain margins in melal ceramic ramie. IntJ Proslhodont 1989;2:459-466. restorations. IntJ Prosthodont 1991;4:508-516. 33. Castellani D, Baccetti T, Giovannoui A, Bernardini UD. 56. Participants of CSP No. 147/242, Morris HF. Department of Resistance to fracture of metal ceramic and all-ceramie Veterans Affairs cooperative studies project No. 242. crowns. IntJ Prosthodont 1994;7:149-154. Quantitative and qualitative evaluation of the marginal fit of 34. Kern M, Knode H, Slrub JR. The all-poreelain resin bonded cast ceramic, porcelain-shoulder, and cast metai crown mar- . Quintessenee Int 1991;22:257-262. gins. I Prosthet Dent 1992;67;198-204. 35. Sorensen (, Knode H, Torres T. In-Ceram all-eeramie bridge 57. Boyle JJ |r, Naylor WP, Blackman RB. Marginal accuracy of teehnology. 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Dent Clin North tal implant system: A ease presentation. Quintessenee Dent Amer 1985;29Í4):7O5-717. Tech 1993:49-59. 64. Adair PJ, Grossman DG. The eastable eeramie erown. Int 1 42. McLean JW. The future of dental poreelain. In: McLean JW Periodont Rest Dent 1984;4(2]:33-46. (ed). Dental Ceramics^Proceedings of the First International 65. Grossman DG. Proeessing a dental eeramie by easting meth- Symposium on Ceramics. Chicago: Quintessence, 1983:33-37. ods. In: O'Brian W[, Craig RG (eds). Conference Proceedings 43. Sieber C. Illumination in anterior teeth. Quintessenee Dent on Recent Developments in Ceramic and Ceramic Metal Tech 1992:81-88. Systems for Crown and Bridge. Ann Arbor, Ml: University of 44. Claus H. The structure and mierostructure of dental porceiain Michigan Press, 1983:19^0. in relationship to the firing condition. Int J Prosthodont 66. Maiament KA. The Dieor eastable eeramie erown. In: Rhoads 1989;2:376-384. JE, Rudd KD, Morrow RM (eds). Dental Laboratory 45. Stannard JG, Marks L, Kanehanatawewat K. Fffeet of multiple fir- Procedures: Fixed Partial Dentures. St Louis, MO: Mosby, ing on the bond strength of seleeted matehed porcelain-fused- 1985:315-330. to-metal combinations. J Prosthet Dent 1990;63:627-629. 67. Maiament KA, Grossman DC. The cast glass-eeramie restora- 46. Mackert JR, Evans AL. Effect of cooling rate on leueite volume tion. J Prosthet Dent 1987;57:674-683. fraction in dental porcelains. J Dent Res 1991;70:137-139. 68. Grossman DC. The science of eastable glass-ceramies. In: 47. Anusavice KJ, Hojjatie B. Effeet thermal tempering strength Preston JD (ed). Perspectives in Dental Ceramies—Proceedings and crack propagation behavior of feldspathie porcelains. I of the Fourth International Symposium on Ceramics. Chicago: DentRes1991;70:1009-1013. Quintessenee, 1988:117-134. 48. Anusavice KJ, Gray A, Shen C. Influenee of initial flaw size on 69. Maiament KA. The cast glass-eeramic crown. 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Eoropaisches Patentamt 1986. 1977;21:787-801. Anmeldung 864007810. France, 4 Nov 1986. 52. Goodaere CJ, Van Roekel NB, Dykema RW, Ullmann RB. 73. Sadoun M. In-Ceram. Presented at the Meeting of the The collarless metal ceramic erown. J Prosthet Dent 1977; American College of Prosthodontists, 3 Sept, 1990. 38:615-622. 74. Claus H. Vita In-Ceram, a new system for producing alu- 53. Hinriebs RE, Bowles WF 111, Huget EF. Apparent density and minum oxide crown and bridge substructures. Quintessenz tensile strength of materials for facially butted porcelain mar- Zahntechnik 1990;16:35-45. gins. J Prosthet Dent 1990;63:403-407. 75. Levy H, Daniel X. Working with the In-Ceram porcelain sys- 54. Belles DM, Cronin RJ Jr, Duke ES. Effeet of metal design and tem. ProthDentN 1990; 13:2-11. technique on the marginal characteristics of the collarless 76. Probster L, Diehl J. Slip-casting alumina ceramies for crown metal ceramic restoration. J Prosthet Dent 1991 ;65:611-619. and bridge restorations. 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77. Futterknecht N, linoian V. A renaissance oí ceramic proslhel- 100. Delong R, Sasik C, Pinlado MR, Douglas WH. The wear of ¡CS? Quintessence Deni Tech 1992:65-78. enamel when opposed by ceramic systems. Dent Mater 78. Ironside |G. Light transmission ot a ceramic core malerial 1989:5:266-271. used in fixed prosthodontics. Quintessence Dent Tech 1993: 101. Seghi RR, Rosenstiel SF, Bauer P. Abrasion of human enamel 103-106. by different dental ceramics in vitro. J Dent Res 79. Kappert H, Knode H. In-Ceram: Testing a new ceramic nialer- 1991;70:221-225. ial. Quintessence Dent Tech 1993:87-97. IÜ2. lacobi R, Shillingburg H, Duncanson M. Abrasiveness of 80. Smith TB, Kelly JR, Tesk )A. Fracture behavior ot In-Cerani gold and eight ceramic surfaces against tooth structure and PFM crowns labstracl 17221. ) Deni Res 1992;7I:321. labstracl 1701].) Den Res 1989;68:394. 81. Dong IK, Luthy H, Wohlwend A, Scharer P. hieat-pressed ce- 103. Krejci I, Lutz F, Reimer M, Heinzmann JL. 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Strength of magnesia-core crown wilh 1987;(special issue):66. different body porcelains. Int J Prosthodont 1993;6:60-64. 111. Nathanson D. Dental porcelain technology. In: Garber DA, 89. Q'Brien WJ. Magnesia ceramic jacket crowns. Dent Clin Goldstein RE, Feinman RA (eds|. Porcelain Laminate North Amer 1985;29(4):719-723. Veneers. Chicago: Quintessence, 1988:24-35. 90. O'Brien W|, McPhee FR, Seluk LW. Strength of a high-expan- 112. Tjan AHL. Bond strengths of light-cured composite cement sion core porcelain. In: Preston JD (ed). Perspectives in Dental systems to etched glass ceramic [abstract 881]. J Dent Res Ceramics—The Proceedings of the Fourth International 1988;67(specialissue):223. Symposium on Dental Ceramics. Chicago: Quintessence, 113. Tjan AHL, Dunn JR, Sanderson IR. Microleakage patterns of 1988:167-174. porcelain and castable ceramic laminate veneers. J Prosthet 91. Binns D. The chemical and physical properties of dental Dent 1989;61:276-2ai. porcelain. In: McLean |W (ed). Dental Ceramics—Proceedings 114. Barkmeier WW, Latta MA. Shear bond strength of Dicor of the First International Symposium on Ceramics, Chicago: using resin adhesive systems and light-activated cement. J Quintessence, 1983:41-82. Esthet Dent 1991 ;3(2):95-99. 92. jones DW. The strength and strengthening mechanisms of 115. Ferrari M. Cement thickness and microleakage under Dicor dental ceramics. In: McLean JW (ed). Dental Ceramics— crowns; an in vivo investigation. Int I Prosthodont 1991; Proceedings of the First International Symposium on Ceramics. 4:126-131. Chicago: Quintessence, 1983:83-141. 116. Sorensen JA, Engelman MJ, Torres TJ, Avera SP. Shear bond 93. Baker PS, Clark AE Jr. Compositional influence on the strength of composite resin to porcelain. Int J Prosthodont strength of dental porcelain. Int I Prosthodont 1993;6: 1991;4:17-23. 291-297. 117. Sorensen JA, Kang SK, Avera SP. Porcelain-composite inter- 94. Kelly |R, Giordano R, Pober R, Cima MJ. 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123. Grunder U, Strub |R. Implant-supported suprastructure de- 129. Ishikawa-Nagai S, Sato R, Furukawa K. Using a computer sign. Int) Periodont Rest Dent 1990;10:19-39. color matching system in color reproduction of porcelain 124. Neeser S. Esthetic solutions for fixed partial restorations with restorations. Int) Prosthodont 1992;5:495-502. osseointegrated implants. Quintessence Dent Tech 1993: 130. Monsenego C, Burdairon G, Clerjaud B. Fluorescence of 9-15. dental porcelain. ) Prosthet Dent 1993;69:106-113. 125. Duncan )D, Swift E Jr. Use of lissue-tinted porcelain to re- 131. Riley EJ, Filipancic JM. Ceramic shade determination: store soft-tissue defects. J Prosthod 1994;3:59-61. Current technique for a direct approach. Int ) Prosthodont 126. Clark EB. An analysis of tooth color. | Am Dent Assoc 1933; 1989;2:131-137. 18:2093-2103. 132. Groh CL, O'Brien W), Boenke KM. Differences in color he- 127. Sproull RC. Color matching in dentistry. Part I. The three- tween fired porcelain and shade guides. Int J Prosthodont dimensional nature of color. ) Prosthet Dent 1973;29: 1992:5:510-514. 416-424, 133. Sproull RC. Color matching in dentistry. Part II, Practical ap- 128. Preston JD. The elements of esthetics' application of color plications of the organization of color. ) Prosthet Dent science. In: McLean ]W (ed). Dental Ceramics- 1973;29:556-566. Proceedings of the First International Symposium on 134. What I Believe—Bartlette's Book of Familiar Quotations, ed Ceramics. Chicago: Quintessence, 1983:491-520. 9. Little, Brown, & Co, 1930.

Literature Abstract •

Direct replacement of failed CP titanium implants with larger-diameter, HA-coated TÍ-6AI-4V implants: Report of five cases

The principles of initially mandated that when an implant fails to osseointe- grate, the implant must be removed and a 1-year healing period musí transpire before placement of a second implant into the same location. More recently, numerous studies have reported the successful piacement of endosseous implants into tooth extraction sites. The surgical technique for tooth extraction sites includes flattening crestal irregularities, de- briding the extraction sites, site reshaping and deepening, and guided tissue regeneration as indicated. Therefore, the question arose as to whether the surgical techniques successful with tooth extraction sites can be applied to the sites of failed implants. This clincal report describes five situations in which 3.75 mm diameter commercially pure titanium (CP Ti) screw-type implants (Swede-Vent Implants, Dentsply, Encino, CA) were immediately re- placed with 4.25 mm diameter hydroxyapatite-coated {)HA-coated) titanium alloy (TÍ-6AI-4V) ledge-type implants (Micro-Vent Impiants, Dentsply). In all five clinical situations implant fail- ure had occurred within 6 months of initial implant placement and before prosthodontic pro- cedures were initiated. Six months after placement of the second implant, the implants were exposed, healing abutments were placed, and prosthodontic treatment was initiated. All five patients were followed for a minimum of 3 years. During this time, all implants successfully maintained osseointegration and exhibited less than 1 mm of overall crestal bone loss. The authors conciuded that a 1-year healing period after implant removal may not be necessary provided that the site can be reprepared to eiiminate thread grooves and invasive soft tis- sue, the replacement implant is larger in diameter than the original implant, and sufficient bone remains for the replacement procedures. While the findings of this limited clinical re- port must be considered preliminary, the implant replacement procedures described merit additional scientific evaluation.

Evian CI, Cutler SA. Int J Oral Maxillofac Implants ^995'.^0'.736-743. References: 32, Reprints: Cyril I. Evian, 1000 Valley Forge Towers, Suite 112, King of Prussia, Pennsylvania 19A06.~nichard R. Seals. Jr, DDS, MEd. MS, Department of Prosthodontics. The University of Texas Health Science Center at San Antonio. San Antonio. Texas

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