The InterdisciplinaryRelationship Between

Prosthodontics andDental Technology

Kenneth A. Malanient, DDS, MScD*Tufts LJniversityBoston, Massachusetts

Nicola Pietrobon, CDT**University of ZurichZurich, Switzerland

Stephan Neeser, CDTInprotek Dental LaboratoryBoston, Massachusetts

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

Over the last decade dental technology, dentalscience, and dental practice have advanced

dramatically, greatly expanding and improving thechoices of materials and techniques. The most im-portant issues in dentistry today are not aboutwhich material, color, or technique is best. Themost significant issues are interpersonal. In spite ofthe potential for a unique collaboration betweenthe prosthodontist and the dental technician.

'Lecturer, Post-Craduate Prosthodontics and Periodontics;Private Practice, Boston, Massachusetts.

**Head of Dental Technology, Department of Prosthodontics.

Reprint Requests: Dr Kenneth A. Malament, 50 StanifordStreet, Boston, Massachusetts 02114.

Presented by Mr Pietrobon at the International Society ofDental Ceramics, Young Speaker of the Year Competition,lOth Internationa! Symposium on Ceramics, New Orleans,Louisiana, 31 May-2 ¡une 1991; and at the NortheasternGnathological Society Meeting, New York, New York, 17April 1992.

education in each discipline fails to support this in-teraction; in practice, communications breakdown, and practical problems result.

Cooperative goals must be established and betterways to share knowledge must be found. Whenprosthodontists and technicians each understandthe many variables and problems the other faces,they can work as a team, helping one another toidentify significant facts and potential difficultiesposed by specific dental materials, techniques, orstages of the work in progress. In this way both dis-ciplines share responsibility for treatment plansbased on mutual understanding. An appreciationof the objectives and responsibilities of each disci-pline ultimately helps the individual to advance in-dividual professional goals.

This article outlines the steps in prosthesis fabri-cation and emphasizes areas of difficulty for theprosthodontist of which the technician might not beaware, as well as areas of difficulty for the techni-cian of which the prosthodontist might not beaware. 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 andProsthodontists

The mandate and responsibility of the prosthodon-tist is to restore patients' oral function to improvethe health, comfort, and appearance. The specialtycontributes to the general practice of dentistry byproviding expertise in diagnosis, treatment plan-ning, and proper care sequencing. The AmericanDental Association's Standards for AdvancedSpecialty Education Programs in Prosthodonticscall for an in-depth knowledge and clinical com-petency in fixed, removable, implant, and maxillo-facial prosthodontics.

Laboratory procedures that must be mastered bythe technician (and understood by the prosthodon-tist) are diagnostic waxing, provisional restoration,master dies, framework or core fabrication, veneerfabrication, and occlusion.

The dental technician supports the prosthodontist'seffort in many ways. Indeed, dental technicians havemade major contributions to dental materials sci-ence. A standard for excellence in dental ceramicswas established by Dicor glass-ceramic (DentsplyInternational, York, PA), which was researched anddeveloped by Peter Adair and Dr David Grossman atGorning Glass Works; Empress glass-ceramic(Ivoclar, Schaan, Liechtenstein) was researched byArnold Wohiwend at the University of Zurich,Zurich, Switzerland; Creation iridescent feidspathicporcelain Oensen, North Haven, CT) was researchedby Willi Geller; Vintage/Opal feidspathic ceramic(3M-Unitek, Monrovia, CA) was researched byMakoto Yamamoto; and Omega and Alpha opales-cent feidspathic ceramic (Vita, Bad Säckingen,Germany) was researched by Claude Sieber. TheAlpha ceramic greatiy improved the color propertiesof Vita's In-Ceram glass-ceramic, which had beendeveloped by Dr Michael Sadoun, a dentist. Theseand other ceramic materials, equipment, and newforming techniques have improved the marginal fitand optical properties of dental prostheses and havesubstantially affected dental practice.

Cooperation in Developing a Dental Prosthesis

Cooperation between prosthodontists and dentaltechnicians rests on a mutual appreciation of theanatomic deficiencies that limit the esthetic resultin prosthodontics. In describing the esthetic factorsrelated to teeth. Miller^ noted that teeth have boththree-dimensional (form) and two-dimensional (sil-houette) visual properties. The nature of the gingi-val framing or dark spaces around teeth affectstheir symmetry. Although Stein and Kuwata^ and

Preston and Bergen^ have established requirementsand discussed factors involved with tooth color.Stein" described the esthetic appearance of teeth ascontrolled more by form and the emergence profilethan by color.

There are many steps in building a successfulprosthesis, and the temptation to combine or omitsteps should be resisted.

Diagnostic Waxing

An accurately mounted diagnostic cast is preparedto resemble the planned tooth preparations. Thediagnostic waxing, made on this cast, reestablishesproper arch form, occlusal plane and form, toothcontours, and esthetics. It can be used as a blue-print for both the provisional and definitive restora-tion.-'' Computer imaging is helpful in initially di-recting thought regarding the patient's estheticdesires in planning the diagnostic waxing. Thewaxing procedure, however, defines three-dimen-sional problems that both the prosthodontist andtechnician wi l l encounter and must resolve.Furthermore, the diagnostic waxing can be helpfulas a teaching model. The patient can understandproblems better by seeing them and discussingthem with the prosthodontist. This information canbe shared with the technician, and needed alter-ations can be easily made.

Provisional Restorations

Ideally, a provisional acrylic resin restorationshould be flasked and heat processed. The diag-nostic waxing can provide the form for the resinteeth. The technician can make the provisionalrestoration in acrylic resin alone, or the resin maybe supported by a metal framework. The prostho-dontist should let the technician know that an all-resin restoration can be more convenient, espe-cially when it replaces an existing prosthesis andwhen the underlying form of the tooth preparationis not known. If the prosthodontist needs to createadditional space in the provisional restoration, thetask will be more difficult and frustrating if a metalframework, as well as the resin, must be reduced.An all-acrylic resin prosthesis is usually preferredfollowing initial tooth preparation.

A long-term provisional restoration is ideal forpatients who have long edentulous spans or whowill be undergoing extensive periodontal surgeryand will require substantial time for healing.^ Animpression of the tooth preparations is made, andthe casts are accurately mounted on an articulator.A metal framework is cast to fit the dies, which

The Internationai Jotirnai of Prosthodontics 3 4 2 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 resinafter the relining process. Acrylic resin teeth can beused or the teeth can be manually waxed, and thefinished waxed margins can be established on thismetal and stone cast. The stone cast, metal frame-work, and wax or resin are embedded in stone andflasked for acrylic resin processing. Alternatively,the technician can completely wax the forms, flask,eliminate the wax, and pack complete acrylic resinforms on the metal framework. The metal frame-work in this type of provisional prosthesis makes itrelatively fracture resistant.

Master Dies

The new generation of poly(vinyl siloxane) or poly-ether impression materials produces highly accu-rate, stable dental impressions that can be pouredmany times to produce accurate stonecasts.'i"^-"*' It is helpful if the prosthodontist usesthese newer, more stable impression materials thatdo not require immediate pouring, and thereforedo not force technicians to interrupt sensitive pro-cedures or disturb their concentration.

Previous die systems used plaster bases and weremore likely to distort because of the unpredictableexpansion properties of setting gypsum. Newer mas-ter die systems, such as the Zeiser^ (Zeiser, GirrbachDental, Santa Rosa, CA) and Kiefer Systems (Vita),use indexed resin bases that have improved die po-sition accuracy and stability."™"'"' Such die sys-tems allow greater accuracy of the die-master castrelationship following sectioning. The demand forthese types of systems is increasing as more dentistsattempt to complete restorations without trial place-ment procedures. These systems are also popularwith dentists who use all-ceramic materials for fixedpartial dentures; all-ceramic prostheses must bemade in one piece because they cannot be sol-dered. Unfortunately, many variables, including thedimensional changes of the impression material orsetting stone, still have the potential to distort thepositional accuracy of a sectioned masterC25t 7(77-87,89-103) -p^al placement procedures shouldnot be omitted until further improvements are madein pin and individual die stability.

Tooth Preparation

A strong, well-fitting, and esthetically pleasing den-tal restoration absolutely requires proper toothpreparation. Black' established length, width, taper.

Fig 1 Complete stioulder tooth preparations.

resistance form, and finish line design as the physi-cal factors crucial to a long-lasting prosthesis. Evenwith the recent improvements in dentin bondingmaterials and luting agents, proper attention totooth preparation cannot be ignored. Many authorshave described the merits of different margin de-signs. Shoulder or chamfer preparations have beenadvocated for use with all-ceramic materials.'"Friedlander et a l " " ' ^ and Bernal et al'"' have shownthat shoulder preparation (Fig 1 ), with its buttressingqualities, produces strong all-ceramic crowns thatresist fracture forces better than crowns with cham-fer margins. Stein and Kuwata,^ McLean,'^Preston,'^ and Mi l le r " have advocated propertooth reduction for dental ceramics. All authorshave suggested a minimal reduction of 1.4 mm forany type ofdental ceramic. Ample reduction allowsthe technician to make a strong ceramic restorationwith good color developed by layering or stratifica-tion methods. Mi l ler" has demonstrated that atleast 0.7 mm of ceramic veneer is needed for thedevelopment of correct tooth color.

When preparing teeth, the prosthodontist mayhave to deal with poor visibility, poor preparationanatomy, or awkward handpiece control. Theseproblems can affect tooth preparation form andmargin definition. When a shoulder finishing lineis improperly finished, unsupported or "lipped"areas may result.'^ Such compromised finishingline forms are a source of frustration for dentaltechnicians. It is difficult to make an accurate im-pression of a lip on a margin area, and the result-ing casts are often distorted. The technician hasdifficulty defining or scribing poorly defined finish-ing lines. Waxing procedures are difficult, and thepattern is often distorted during removal from thedie. It is difficult to accurately fit the resultant cast-ings without harming the die. These difficulties can

"-'• 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 ofthe masfer casf.

Fig 3 Anterior composife resin jig made af the desired verfi-cal dimension of occlusion and used fo record cenfric reiafion.

Fig 4 Mefal ceramic impiant prosfhesis wifh gihgiva-coloredfeldspafhic porcelain.

ulfimately result in a completed restoration thaf iseifher foo loose, or that fits so fightly that pressurescreated during luting fracture a ceramic margin.

Even when the greatest care is faken, a problemusually compromises ideal margin form. Hand in-struments or tissue-safe end-cuffing shoulder bursare helpful in properly flaftening fhe toofh prepara-fion and preventing and reducing fhe pofenfiai forthe formafion of a iip,

Intraoral Records

Intraoral records may include centric relationrecords, facebow recordings (mean value or kine-matic), or panfographic fracings. The fechniciancan collaborafe by making centric reiafion guides(Figs 2 fo 4) at an arbitrary verticai dimension, and

making rims that can be positioned on teeth or im-pianfs wifh cenfrai bearing poinf piafes to assistfhese procedures," Bofh of these laboratory de-vices heip fhe prosthodontist fo make accuratecentric relation records af a desired vertical dimen-sion, A panfographic record may be used fo recordexcursive 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 pantographicfracings. Casts can be mounted on the articulatorwifh fhe facebow and cenfric reiafion records.

Treatment Waxing

This simple procedure, whiie adding exfra cosf andtime, produces considerable benefits because itsubstantially improves the understanding, commu-nication, and collaboration between fhe prosfho-donfisf, denfal technician, and patient,^ It is a triaiplacemenf waxing, made from toofh- and gingiva-colored wax (Chroma Wax, Benzer Denfal, Zurich,Switzerland) (Figs 5 and 6) that allows ali parties topreview fhe esthetic resuit anticipated for the defini-tive prosthesis. The wax should be tooth-colored,^'because a patient cannot easily relate to coloredwax teeth. The frial waxing is complefed on themaster dies and can be tried in fhe moufh and usedto tesf fhe confour and shape of the most simple an-terior unit or a complex complete rehabilitation. Inedenfulous pafienfs whose treatment involves com-plete implanf prosfhodonfics, arfificial feeth can bearranged on a frial denfure base (Figs 7 fo 10), Thisis 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. Thesecan be adjusted to correct esthetic deficiencies.

Fig 6 Anterior Empress ail-ceramic restorations made fromtreatment-wax forms.

Fig 7 Artificiai teeth arranged on a triai denture base tomeet the patient's individuai esthetic and tunctionai needs.

Fig 8 The wax treatment denture converted to treatmentwaxing connected to the impiants.

Fig 9 Metal ceramic implant framework designed to supportboth tooth- and gingiva-coiored porceiain.

Fig 10 Metal ceramic maxillary implant prosthesis.

9. Number 4, 1996 345 The Internationai Journai of Prosthodontics

Prostbodontics and Dental Technology

Fig 11 Worn composite resin restoration repairing a frac-tured tooth.

Fig 12 Metal ceramic 36O.degree collarless teldspathicporcelain complete-coverage restoration.

esthetic and functional needs. The wax treatmentdenture can then be converted to an accurate im-plant treatment waxing. Getting the patient's ideasabout appearance during the treatment waxingstage can be most helpful and can reveal errors intooth or pontic piacement. Although computerimaging is useful for providing alternative workingplans quickly, it does not provide as much real pa-tient information as does the treatment waxing.Often the computer image does not reflect prob-lems that are apparent on the master cast or in themouth. Digitai images present a two-dimensionalillusion that cannot be touched or seen directly inthe patient's mouth, whereas a technician orprosthodontist can directly alter the treatment wax-ing to develop optimal form and contour. Even withthe diagnostic waxing and casts of the provisionalrestorations, large discrepancies may exist betweenthe first treatment waxing and the patient's estheticdesires. The treatment waxing may be easily al-tered. An impression may be made of the acceptedcomplete contour waxing to make an index. Thistooth contour guide form allows the technician tofabricate restorations having optimal strength, accu-rate occlusion, and the desired optical properties.The dentist's common practice of viewing ceramicrestorations just prior to glazing can lead to prob-lems if major alterations are needed. After large al-terations, the ceramic material may no longer beproperly supported by the metal framework.Furthermore, if the dentist grossly alters contours inthe preglaze phase, color effects may be perma-nently lost. Ceramic color is best developed bystratifying different opaque and translucent porce-lains, and technicians spend much time developingthese subtle but essential effects.'^'^^"^''

Chroma Wax, developed by Wohlwend, andother tooth-colored waxes can be highly accurateand burn out properly. These complete-contourwax teeth can be reproduced in gold alloy, glass-ceramic, or press-formed ceramic.

Selection of Dental Materials

Materials for fixed prostheses continue to improvein strength, marginal accuracy, and color.Although ceramic materials are the most estheti-cally pleasing, debate continues as to whether all-ceramic or metal ceramic materials are prefer-able.^''"^^ The answer lies in the education andtalent of individual dental technicians and prostho-dontists, and in the treatment plans upon whichthey agree. Color communication, tooth form,opacity, translucency, fit, and biocompatibilitymust all be addressed. Currently, all-ceramic mate-rials are useful only as individual restorations, al-though some have potential as short-span can-ti lever or three-unit anterior f ixed partialdentures.^^"^' Metal ceramic restorations continueto be the state of the art.^^'^'*''"'''" They are the mostversatile materials and can be used in any situa-tion, as a single-unit restoration or within the mostcomplex complete fixed or implant prosthesis, pro-vided there is sufficient space to ensure that theprosthesis will have the necessary strength to with-stand oral forces.

The prosthodontist must be aware of advances inmetal ceramic techniques. The color properties ofmetal ceramic restorations can be competitive withall-ceramic restorations (Figs 4 and 9 to 18). Thetechnique of ceramic stratification,' described byGeller and Wohlwend (unpublished data),

The International )ournal ot Prostbodoi 3 4 6 Volume 9, Number 4, 1996

Prosthoclontits and Dental Technology

Fig 13 This patient required a complete reconstruction be-cause of worn restorations, periodontal disease, and caries.

Fig 14 Maxillary metal ceramic reconstruction for fixed par-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-ance of the In-Ceram and metal ceramic restorations. The In-Ceram copings were veneered with feldspafhic porcelain.

Fig 16 This patient required anterior restorations to correctexisting esthetic deficiencies.

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 individualDicor 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 marginsand decay necessitated a complete reconstruction.

Fig 20 The completed reconstruction using Empress all-ce-ramic anterior restorations to the premolars and Ih-Ceram all-ceramic posterior restorations.

McLean,''^ and Sieber,"*̂ has significantly enhancedceramic fabrication. The use of computer-controlledceramic furnaces and improved insulation has madeceramic processing more predictable."""™ Anotheradvance is in the more stable, accurate, and translu-cent color properties of shoulder porcelain.^'"^'Opalescent feldspathic ceramic materials such asOmega, Creation, or Vintage possess an importantcolor quality of natural teeth previously lacking inmetal ceramic restorations.

Nonetheless, the visibility of the metal frame-work necessitates the addition of an opaque porce-lain layer that interferes with the ideal optical ef-fect of metal ceramics. This requirement hasnurtured interest in all-ceramic materials that couldeliminate the metal framework entirely. Althoughall-ceramic crowns have been in use for the pastcentury, the porcelain jacket was the first generallyaccepted all-ceramic material.^^"^^ As the scienceof dental ceramics improved, materials such asCerestore (Coors Ceramic, Colorado),^^ Dicor(Dentsply)''' '-'' ' ' (Figs 17 and 18), Cerapearl(Kyocera Bioceram Group, Kyoto, Japan),™''' In-Ceram (Vident, Baldwin Park, CA)"-™ (Figs 14 and15), and Fmpress (Ivoclar North America, Amherst,|sjY)8i-85 (pjg5 5̂ 19^ and 20) were developed.These materials are organized crystalline forms,unlike feldspathic dental porcelain. Improved ma-terials for feldspathic-based porcelain have beendeveloped and include Renaissance (Williams,Amherst, NY),•">•"' Captec (Leach and Di l lon,North Attleboro, MA), and magnesia ceramic.ä^"'"

Glass-ceramic materiais are significantly strongerthan dental feldspathic porcelain, but are not as

strong as metal ceramic restorations.'^'^^''^'"-" Asthe more desirable strength of ceramics is im-proved, so is its inherent opacity. The color proper-ties of all glass-ceramic maferials require veneeringwith feldspathic porcelain layers (Figs 21 and22) . " Color may be easiest to develop over aglass-ceramic core,'* particularly because of thecontinuing improvements in the quality of the dif-ferent veneering porcelains and infusion glasses(In-Ceram, Vident). Wear continues to be a factorwith feldspathic porcelain because it is more abra-sive than tooth enamel.'™"'"^ Although the Dicormaterial appears to be less abrasive to toothenamel, most clinical conditions require veneeringDicor with feldspathic porcelain. With the contin-ued development of dentin bonding, ceramic acid-etching, silanation, and resin luting, the fracturerafes of all-ceramic materials are decreasing sub-stantially.'''' '"'"'^^ Thus, the continuation of re-search, development, and use of these materials isassured.

Ceramic Oral Mucosa Simulation

Gingiva-colored ceramics have been developedsufficiently so that they are now suitable for eithertooth- or implant-supported fixed prosthodon-(¡(,5123-125 ji^gy 3|.g u jg j (Q recreate normal mu-cosal contour and are particularly effective in flat,edentulous areas or in areas with residual ridge de-fects (Figs 2, 4, 10, 23, and 24). They also can im-prove tooth-gingiva symmetry or correct gingivaldefects that cannot be repaired surgically. Finally,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),Nofe thaf the color is low value and perceived by the pafientas "gray," Three surface coloring procedures were made onfhe compiefe confour casfing.

Fig 22 A new maxillary leff compiefe coverage restoration(Dicor), Note fhat fhe color is more pleasing because a Dicorcoping veneered wifh feldspafhic porcelain provided greaterdepth of color and opacify.

Fig 23 Mefal ceramic framework designed fo supporf footh-and gingiva-colored feldspathic porcelain. The framework isdesigned fo allow small spaces and gingival embrasures be-fween ceramic gingiva and feefh.

Fig 24 Denfal and gingival feldspafhic porcelain fixed partialdenture thaf replaces missing feefh and compensates a largeresidual ridge defecf.

plants, and offer the advantage of being easy toclean. Development and improvements in differenfgingiva-colored porcelains are continuing.

Selection of Color

Clark,""- Sproull, '" and Preston and Bergen^ de-scribe tooth color as a function of hue, chroma, andvaiue. Factors thaf influence fhe absorpfion and re-flection of light (opacify, franslucency, opalescence,iridescence, and phosphorescence) are of major im-portance. An individual's physical abiiify to per-ceive and interpret light data is essentiai to describ-ing coior. The different areas of a footh have

differenf color properties. Opaque and translucentareas in feeth, and even fhe size, shape, and colorof fhe gingivai frame, are important facfors fhafmusf be described before an individuai foofh coiorcan be developed,'-3'"Ä24,40,i28

Toofh shade decisions are difficult,'^'-'" In theend, fhe communication between the prosthodon-tist and the technician is based on estimation modi-fied by numerous facfors involving training, experi-ence, environment, and acuify of percepfion.Ideally, color should be described before any freaf-ment by the dentist is inif iafed, Riley andFilipancic"' have shown fhaf teeth dry out whenfhe mouth is open during denfai freafment, and

"" ' ••ne 9, Number 4, 1996 3 4 9 The Internationai Journal of Prosthodontics

Prosthoclonlics 3nd Denial Technology Malament et

Fig 25 Dicor castings made trom a custom shade tab mold.Feldspathic porceiain is appiied to ttiese tabs to deveiop indi-viduai color records tor anterior restorations. The tab castingsare made in the actuai coping materiai that wiii iater be used.This estabiishes a more accurate record and better taciiitatescommunication and understanding between prosthodontistand laboratory technician.

Fig 26 Custom coior tab has been made and examined inthe patient's mouth. The tab ooior can be shown to the patientfor a reaction. The tab can be photographed compared to thenaturai teeth, restorations, or commerciai shade tabs. Thisphotograph is a record that can be sent to a iaboratory techni-cian to highiight deficiencies requiring correction.

such desiccation significantly changes the toothcoior. The environment also influences shade deci-sions, since fhe time of day and variations in artifi-cial light can affecf shade recordings. Miller' hasdemonstrated that present dental shade guides donot represent the range of color in respect to hue,chroma, or value found in natural teeth. Further-more, the poor quality control of dental shadeguides results in inconsistent, often inaccurate,color information. Most are not made of dental ce-ramics, but may be made of either acrylic resin orlayered high-fusing quartz-based ceramic.^-'^^Finally, commercial shade guides are generally 3.5mm thick, and are thus inconsistent with the resultsof actual veneering proceduresJ'^-"''"'

Given the limitations on the prosthodontist'sability to determine the proper color of teeth, it ishelpful to involve the patient directly in color deci-sions, and it is essential to involve the fabricatingtechnician. Riley and Filipancic"' have describedthe use of custom-made shade tabs to facilitatecolor selection and development. A metal wax pat-tern former can be made to cast or form customshade cores in metal or glass ceramic (Figs 25 and26). Feldspathic porcelain can then be layered onthe cast core to develop the correct tooth color. Acustom-fabricated shade tab more correctly repre-sents the required color because the individualcore qualities to be used in the prosthesis are rep-resented. The creation of custom color tabs alsohelps the dentist, technician, and patient to under-stand the probiems involved in developing accu-rate tooth color.

Conclusion

Dental technology and prosthodontics create an es-thetic illusion whiie providing function and health.Preston (personal communication) notes that it isimportant to understand which elements of a pros-thesis are illusion and which are reality. Nothing isperfect; indeed, an obsession with creating the per-fect illusion of a natural tooth can confuse our mainresponsibility, which is the patient's long-termheaith. The challenge of prosthodontics is to main-tain the highest standard of patient care.

The problem defined as the difference betweenwhat we have and what we want, can be analyzedand solved in different ways. Systems anaiysis offersthree approaches: First, more information or bettermethods for analyzing existing information may beneeded. Unfortunately, the information prosthodon-tists and technicians rely on is often oversimplifiedor overstated, since it frequently comes fromsources that have a proprietary interest in a particu-lar material or technique. Second, all the avaiiabieinformation may be present, but, because develop-ments in dental science, materials, and techniquescontinually change the way dentistry is provided,new insight into the nature of the problem may beneeded. At the same time, change must be ap-proached with caution, since commerciai ciaimsoften exceed actual ciinicai performance. Dentaltechnicians and prosthodontists should not tai<erisks or reduce practice overhead at the expense ofthe patients' health. A respectful, conservative ap-proach, based on the scientific method, education.

The Internationai Journal of Prosthodontic 350 Voiume 9. Number 4, t996

Ptosthodontics and Dental Technology

and experience, produces the highest standards oftreatment. Within this conservative, educated ap-proach there is still much room for artistic expres-sion and advancement of both new technologiesand the standard or care. As Einstein said, "It's theideal that animates our best actions."'^*'

Third, we may need to look at ourselves and ex-amine whether we are too intellectually comfort-able with the convenient, familiar standard ofknowledge that we possess. Complacency canblock understanding and the ability to work withbetter solutions.

Collaboration between dental technology andprosthodontics fosters an exchange of information,creates opportunities for new insight into the effectsof recent developments, and provides the impetusto improve our standard of knowledge. It results inthe continuous refinement of treatments and the de-velopment of new definitions for clinical practice.Thus, the scarcity of education and training pro-grams for dental technicians poses a serious prob-lem. If prosthodontics and dentistry are to continueto mature, more attention must be paid to, and op-portunities created for, collaboration with dentaltechnology. To truly understand the problems weface, prosthodontists and dental technicians mustlisten to and work closely with each other.

Acknowledgment

The authors would like to thank the members of the Departmentof Prosthodontics at fhe University of Zurich for their contribu-tions to this article.

References

1. Miller LL. Scientific approach to shade matching. In: Preston)D (ed). Perspectives in Dental Ceramics—The Proceedings ofthe Fourth International Symposium on Dental Ceramics.Chicago: Quintessence, 1988:193-208.

2. Stein RS, Kuwata M. A dentist and a dental technologist ana-lyze current ceramo-metai procedures. Dent Clin North Am1977;21:729-749.

3. Preston |D, Bergen S. Color Science and Dental Art. St touis,MO:Mosby, 1980:1-76.

4. Stein RS. Periodontal dictates for esthetic ceramometalcrowns. ) Am Dent Assoc 1987;115:63E-73E.

5. Tarantola C), Becker IM. Definitive diagnostic waxing withlight-cured composite resin. I Prosthet Dent 1993,70:315-319.

6. Nevins M, Skutow HM. The intracrevicular restorative mar-gin, the biologic width, and the maintenance of the gingivalmargin. Int) Periodont Rest Dent 1984:4(3):31-S0.

7. O'Brien WÍ. Dental Materials—Properties and Selection.Chicago: Quintessence, 1989:77-87,89-103,192-194.

8. Zeiser M. ModelUSystem mit kunststoff.sockelplatte ¡etz auchfur kleine labors. Dent tah 1982;30:489-490.

9. Black GV. Operative Dentistry, ed 8. Woodstock, IL: Medico.Dental, 1947.

10. Sorensen |A, Torres Tj, Kang SK, Avera SP. Marginal fidelity ofceramic crowns with different margin designs labstract 1365|.I Dent Res 1990:69:279.

11. Friedlander LD, Munoz CA, Coodacre C|, Doyle MC, MooreBK. The effect of tooth preparation on the breaking strength ofDicor crowns: Part 1. Int I Prosthodont 199O;3:1S9-168.

12. Friedlander tD , Munoz CA, Coodacre C), Doyle MG, MooreBK. The effect of footh preparation on the breaking strength ofDicor crowns: Part 2. Int) Prosthodont 1990;3:241-248.

13. Friedlander LD, Munoz CA, Goodacre CJ, Doyle MG, MooreBK. The effect of tooth preparation on the breaking strength ofDicor crowns: Part 3. Int I Prosthodont 1990;3:327-340.

14. Bernai G, Iones RM, Brown DT, Munoz CA, Goodacre CJ.The effect of finish line form and luting agent on the breakagestrength of Dicor crowns. Int 1 Ptosthodont 1993;6:286-29ü.

15. McLean |W (ed). The Nature of Dental Ceramics, monograph1, The Science and Art of Dental Ceramics, vol I. Chicago:Quintessence, 1979:23-51.

16. Preston ID. Rational approach to tooth preparations for cetamo.metal restorations. Dent Clin North Am 1977,21:683-698.

17. Miller LL. A clinician's interpretation of tooth preparation andthe design of metal substructures for metal ceramic restora.tions. In: McLean ]W (ed). Dental Ceramics—Proceedings ofthe First International Symposium on Ceramics. Chicago:Quintessence, 1983:153-206.

18. Malamenf KA. Considerations on posterior glass.ceramicrestorations. Int) Petiodont Rest Dent 1988;8(4):33-50.

19. Rieder CE. The use of provisional restorations to develop andachieve esthetic expectations. Int ) Periodont Rest Dent 1989:9:123-139.

20. Guichet NF. Principles of Occlusion. Anaheim, CA: Denat,1970:37-66.

21. Roge M, Preston )D. Color, light and the perception of fotm.Quintessence Int 1987;18:391-396.

22. Yamamoto M. Metal ceramics. Chicago: Quintessence,1985:268^02.

23. Kedge M. Lateral segmental build.up. In: Preston )D (ed).Perspectives in Dental Ceramics—Proceedings of the FourthInternational Symposium on Ceramics. Chicago: Qu in .tessence, 1988:369-374.

24. McLean JW, leansonne EE, Chiche G, Pinault A. AlUceramiccrowns and foil crowns. In: Chiche CJ, Pinault A (eds).Esthetics of Anferior Fixed Prosthodontics. Chicago: Quin-tessence, 1994:75-111.

25. Campbell SD. A comparative strength study of metal ceramicand ail.ceramic esthetic materials: Modulus of rupture. JProsthet Dent 1989;62(4):476-479.

26. Sorenson )A, Qkamoto SK. Comparison of marginal fif of all-cetamic crown systems [abstract 1415]. J Dent Res 1987:66:283.

27. Scharer P, Sato T, Wohlwend A. A comparison fit of the mar.ginal fit of three cast ceramic systems. J Prosthet Dent 1988:59:534-542.

28. Wohlwend A, Strub JR, Scharer P. Metal ceramic and al l .porce la in restorations: Current considerat ions. Int JPtosthodont 19a9;2:13-26.

29. Seghi RR, Sorensen JA, Engelman MJ, Roumamas E, Torres DJ.Flexutal strength of new ceramic maferials [absfract 1521]. JDent Res 1990:69:299.

30. Drummond JL, Novickas D, Lenke JW. Physiological aging ofan all.ceramic restorative material. Dent Mater 1991:7:133-137.

31. Scherrer SS, de Rijk WG. The fracture resistance of a l l .ceramic crowns on supporting structures with different elasticmoduli. Int) Prosthcdonf 1993:6:462-467.

Volume 9, Nutnber 4, 1996 351 The International Joumal of Ptosthodontics

Prosthodontics and Dental Technology

32. Campbell SD, Kelly JR. The influence of surface preparationon the strength and surface mieroslrueture of a east dental ee-ramie. IntJ Proslhodont 1989;2:459-466.

33. Castellani D, Baccetti T, Giovannoui A, Bernardini UD.Resistance to fracture of metal ceramic and all-ceramiecrowns. IntJ Prosthodont 1994;7:149-154.

34. Kern M, Knode H, Slrub JR. The all-poreelain resin bondedbridge. Quintessenee Int 1991;22:257-262.

35. Sorensen (, Knode H, Torres T. In-Ceram all-eeramie bridgeteehnology. Quintessenee Dent Tech 1992:41-46.

36. Kern M, Sehwarzbaek W, Strub IR. Stability of all-poreelainresin-bonded fixed restorations with different designs: An invitro sludy. IntJ Proslhodont 1992;5:108-113.

37. Probster L. Survival rate of In-Ceram restorations, int JProsthodont 1993;6:259-263.

36. Kern M, Douglas WH, Feehtig T, Strub JR, Delong R. Fraeturestrength of all-porcelain, resin-bonded bridges after testing inthe artificial oral environment. J Dent 1993;21:117-121.

39. Kern M, Feehtig T, Strub JR. Influence of water storage andthermal cyling on the fracture strength of all-porcelain, resin-bonded fixed partial dentures. J Prosthet Dent 1994;71:251-256.

40. Steger E. Color reproduction for the young and elderly. In:Preston JD (ed). Perspectives in Dental Ceramies—Proceedings of the Fourth International Symposium onCeramics. Chieago: Quintessenee, 1988:251-255.

41. Neeser S, Weber HP. Restorative procedures with the ITI den-tal implant system: A ease presentation. Quintessenee DentTech 1993:49-59.

42. McLean JW. The future of dental poreelain. In: McLean JW(ed). Dental Ceramics^Proceedings of the First InternationalSymposium on Ceramics. Chicago: Quintessence, 1983:33-37.

43. Sieber C. Illumination in anterior teeth. Quintessenee DentTech 1992:81-88.

44. Claus H. The structure and mierostructure of dental porceiainin relationship to the fir ing condit ion. Int J Prosthodont1989;2:376-384.

45. Stannard JG, Marks L, Kanehanatawewat K. Fffeet of multiple fir-ing on the bond strength of seleeted matehed porcelain-fused-to-metal combinations. J Prosthet Dent 1990;63:627-629.

46. Mackert JR, Evans AL. Effect of cooling rate on leueite volumefraction in dental porcelains. J Dent Res 1991;70:137-139.

47. Anusavice KJ, Hojjatie B. Effeet thermal tempering strengthand crack propagation behavior of feldspathie porcelains. IDentRes1991;70:1009-1013.

48. Anusavice KJ, Gray A, Shen C. Influenee of initial flaw size oneraek growth in air-tempered poreelain. J Dent Res 1991;70:131-136.

49. Fairhurst CW, Lockwood PE, Ringie RD, Thompson WO. Theeffect of glaze on porcelain strength. Dent Mater 1992;8:203-207.

50. Campbell SD, Pelfetier LB. Thermal eyeling distortion ofmetal ceramies. Part 1: Metal eeramie width. J Prosthet Dent1992;67:603-608.

51. Sozio R. The marginal aspect of the eeramo-metal restoration:The eollarless eeramo-metal restoration. Dent Clin North Am1977;21:787-801.

52. Goodaere CJ, Van Roekel NB, Dykema RW, Ullmann RB.The collarless metal ceramic erown. J Prosthet Dent 1977;38:615-622.

53. Hinriebs RE, Bowles WF 111, Huget EF. Apparent density andtensile strength of materials for facially butted porcelain mar-gins. J Prosthet Dent 1990;63:403-407.

54. Belles DM, Cronin RJ Jr, Duke ES. Effeet of metal design andtechnique on the marginal characteristics of the collarlessmetal ceramic restoration. J Prosthet Dent 1991 ;65:611-619.

55. Chaffee NR, Lund PS, Aqu i l i no SA, D iaz -Arno ld A M .Marginal adaptation of porcelain margins in melal ceramicrestorations. IntJ Prosthodont 1991;4:508-516.

56. Participants of CSP No. 147/242, Morris HF. Department ofVeterans Affairs cooperat ive studies project No. 242.Quantitative and qualitative evaluation of the marginal fit ofcast ceramic, porcelain-shoulder, and cast metai crown mar-gins. I Prosthet Dent 1992;67;198-204.

57. Boyle JJ |r, Naylor WP, Blackman RB. Marginal accuracy ofmetal ceramic restorations with porcelain facial margins. JProsthet Dent 1993;69:19-27.

58. McLean JW, Seed IR. The bonded alumina crown. I. The bond-ing of platinum to aluminous dental porcelain in using tinoxide coatings. Aust DentJ 1976;21:n 9-127.

59. McLean JW, Seed IR. The bonded alumina c rown. I I .Construction using the twin foil technique. Aust Dent J1976;21:262-268.

60. Southen D. The porcelain jaekel erown. In: McLean JW (ed).Dental Ceramics—Proceedings of the First International Sym-posium on Ceramics. Chicago: Quintessence, 1983:207-230.

61. Dickinson AJG, Moore BK, Harris RK, Dykema RW. A com-parative study of the strength of aluminous porcelain and all-ceramic crowns. J Prosthet Dent 1989;61:297-304.

62. Mante F, Brantley WB, Dhuru VB, Ziebert GJ. Fracture tough-ness of high alumina core dentai ceramics: The effect of waterand artificial saliva, int J Prosthodont 1993;6:546-552.

63. Sozio RB, Riley EJ. Shrink-free ceramic. Dent Clin NorthAmer 1985;29Í4):7O5-717.

64. Adair PJ, Grossman DG. The eastable eeramie erown. Int 1Periodont Rest Dent 1984;4(2]:33-46.

65. Grossman DG. Proeessing a dental eeramie by easting meth-ods. In: O'Brian W[, Craig RG (eds). Conference Proceedingson Recent Developments in Ceramic and Ceramic MetalSystems for Crown and Bridge. Ann Arbor, Ml: University ofMichigan Press, 1983:19^0.

66. Maiament KA. The Dieor eastable eeramie erown. In: RhoadsJE, Rudd KD, M o r r o w RM (eds). Denta l LaboratoryProcedures: Fixed Partial Dentures. St Louis, MO: Mosby,1985:315-330.

67. Maiament KA, Grossman DC. The cast glass-eeramie restora-tion. J Prosthet Dent 1987;57:674-683.

68. Grossman DC. The science of eastable glass-ceramies. In:Preston JD (ed). Perspectives in Dental Ceramies—Proceedingsof the Fourth International Symposium on Ceramics. Chicago:Quintessenee, 1988:117-134.

69. Maiament KA. The cast glass-eeramic crown. In: Preston JD(ed). Perspectives in Dental Ceramics—Proceedings of theFourth International Symposium on Ceramics. Chicago:Quintessence, 1988:331-342.

70. Hobo S, Iwata T. Castable apatite ceramics as a new biocom-patible restorative material. 1. Theoretical considerations.Quintessence Int 1985;]6:135-141.

71. Hobo S, Iwata T. Castable apatite ceramics as a new biocom-patible restorative material. II. Fabrication of the restoration.Quintessence Int 1985;16:207-216.

72. Sadoun M [ i nven to r j . Eoropaisches Patentamt 1986.Anmeldung 864007810. France, 4 Nov 1986.

73. Sadoun M. In-Ceram. Presented at the Meet ing of theAmerican College of Prosthodontists, 3 Sept, 1990.

74. Claus H. Vita In-Ceram, a new system for producing alu-minum oxide crown and bridge substructures. QuintessenzZahntechnik 1990;16:35-45.

75. Levy H, Daniel X. Working with the In-Ceram porcelain sys-tem. ProthDentN 1990; 13:2-11.

76. Probster L, Diehl J. Slip-casting alumina ceramies for crownand bridge restorations. Quintessenee Int 1992;23:25-31.

The international lournal of Prosthodontics 352 Volume 9, Number 4, 1996

Proslhndonlics and Denlül Technology

77. Futterknecht N, linoian V. A renaissance oí ceramic proslhel- 100.¡CS? Quintessence Deni Tech 1992:65-78.

78. Ironside |G. Light transmission ot a ceramic core malerialused in fixed prosthodontics. Quintessence Dent Tech 1993: 101.103-106.

79. Kappert H, Knode H. In-Ceram: Testing a new ceramic nialer-ial. Quintessence Dent Tech 1993:87-97. IÜ2.

80. Smith TB, Kelly JR, Tesk )A. Fracture behavior ot In-Ceraniand PFM crowns labstracl 17221. ) Deni Res 1992;7I:321.

81. Dong IK, Luthy H, Wohlwend A, Scharer P. hieat-pressed ce- 103.ramies: Technology and slrength. Int I Prosthodont 1992;5:9-16.

82. Luthy H, Dong )K, Wohlwend A, 5charer P. hIeat-pressed ce- 104.ramies: Influence ot veneering and glazing on strength ¡ab-stract 4151.1 Dent Res 1992:72:567.

83. Campbell S, Giordano R, Pober R. Flexural strength ot 105.Empress treated with glaze, veneer, and tuttcoal [abstract6681.1 Dent Res 1993;72:187.

84. Sorensen JA, Avera SP, Fanuscu Ml. Effect of veneer porcelain 106.on all-ceramic crown labstract 1718]. J Dent Res 1992;7t:320.

85. Zaimoglu A, Uctasli S. The strength of a heat-pressed all- 107.ceramic restorative material [abstract 22041. J Dent Res 1993;72:379. 108.

86. Shoher 1. Reinforced porce la in system, concepts andtechniques. Dent Clin North Amer 1985;29(4):805-818.

87. Jarvis RFH. The non-cast metal ceramic system. In: Preston JD 109.(ed). Perspectives in Dental Ceramics—Proceedings of theFourth International Symposium on Ceramics. Chicago: 110.Quintessence 1988;343-352.

88. Liu C-C, O'Brien W|. Strength of magnesia-core crown wilhdifferent body porcelains. Int J Prosthodont 1993;6:60-64. 111.

89. Q'Brien WJ. Magnesia ceramic jacket crowns. Dent ClinNorth Amer 1985;29(4):719-723.

90. O'Brien W|, McPhee FR, Seluk LW. Strength of a high-expan- 112.sion core porcelain. In: Preston JD (ed). Perspectives in DentalCeramics—The Proceedings of the Fourth InternationalSymposium on Dental Ceramics. Chicago: Quintessence, 113.1988:167-174.

91. Binns D. The chemical and physical properties of dentalporcelain. In: McLean |W (ed). Dental Ceramics—Proceedings 114.of the First International Symposium on Ceramics, Chicago:Quintessence, 1983:41-82.

92. jones DW. The strength and strengthening mechanisms of 115.dental ceramics. In: McLean JW (ed). Dental Ceramics—Proceedings of the First International Symposium on Ceramics.Chicago: Quintessence, 1983:83-141. 116.

93. Baker PS, Clark AE Jr. Composit ional inf luence on thestrength of dental porcela in. Int I Prosthodont 1993;6:291-297. 117.

94. Kelly |R, Giordano R, Pober R, Cima MJ. Fracture surfaceanalysis ofdental ceramics: Clinically failed restorations. Inl IProsthodont 1990;3:430-440. 118.

95. Rosenstiel SF, Porter SS. Apparent fracture toughness ofall-ceramic crown systems. I Prosthel Dent 1989;62(5):29-32. 119.

96. Denissen HW, Wijnhoff GFA, Veldhuis AAH, Kalk W. Five-year study of all-porcelain veneer fixed partial dentures. 1

Prosthet Dent 1993;69:464-468. 120.97. Ferro KJ, Myers ML, Gräser GN. Fracture strength of full-con-

toured ceramic crowns and porcelain-veneered crowns oncopings. I Prosthet Dent 1994;71:462-467. 121.

98. Kelly JR, Campbell SD, Bowen HK. Fracture-surface analysisof dental ceramics. J Proslhet Dent 1989;62(5):536-541.

99. Josephson BA, Schulman A, Dunn ZA, FHarwitz W. A com- 122.pressive strength study of complete ceramic crowns. Part II.

J Prosthet Dent 1991 ;65:388-391.

Delong R, Sasik C, Pinlado MR, Douglas WH. The wear ofenamel when opposed by ceramic systems. Dent Mater1989:5:266-271.

Seghi RR, Rosenstiel SF, Bauer P. Abrasion of human enamelby different dental ceramics in v i t ro. J Dent Res1991;70:221-225.

lacobi R, Shillingburg H, Duncanson M. Abrasiveness ofgold and eight ceramic surfaces against tooth structurelabstracl 1701].) Den Res 1989;68:394.Krejci I, Lutz F, Reimer M, Heinzmann JL. Wear of ceramicinlays, their enamel antagonists and luting cements, jProsthel Dent 1993;69:425-430.

Rosenstiel SF, Baiker MA, Johnston WM. A comparison ofglazed and polished porcelain. Int J Prosthodont 1989;2:524-529.Campbell SD. Evaluation of surface roughness and polish-ing techniques for new ceramic materials. J Prosthet Dent1989;61:563-568.O'Keefe KL, Powers, JM, Noie F. Effect of dissolution oncolor of extrinsic porcelain colorants. Int J Prosthodont1993;6:558-563.Bailey LF, Bennett RJ. Dicor surface treatments for en-hanced bonding. J Dent Res 1988;67:925-931.Malament KA, Grossman DG. Clinical application ofbonded Dicor crowns: Two year report [abstract 15231. jDent Res 1990;69:299.Newburg R, Pameijer CH. Composite resins bonded to porce-lain with silane solution. J Am Dent Assoc 1978;96:288-291.Nathanson D, Hassan F. Effect of etched porcelain thicknesson resin-porcelain bond strength [abstract 1107]. J Dent Res1987;(special issue):66.Nathanson D. Dental porcelain technology. In: Garber DA,Goldstein RE, Feinman RA (eds|. Porcelain LaminateVeneers. Chicago: Quintessence, 1988:24-35.Tjan AHL. Bond strengths of light-cured composite cementsystems to etched glass ceramic [abstract 881]. J Dent Res1988;67(specialissue):223.Tjan AHL, Dunn JR, Sanderson IR. Microleakage patterns ofporcelain and castable ceramic laminate veneers. J ProsthetDent 1989;61:276-2ai.Barkmeier WW, Latta MA. Shear bond strength of Dicorusing resin adhesive systems and light-activated cement. JEsthet Dent 1991 ;3(2):95-99.Ferrari M. Cement thickness and microleakage under Dicorcrowns; an in vivo investigation. Int I Prosthodont 1991;4:126-131.Sorensen JA, Engelman MJ, Torres TJ, Avera SP. Shear bondstrength of composite resin to porcelain. Int J Prosthodont1991;4:17-23.Sorensen JA, Kang SK, Avera SP. Porcelain-composite inter-face microleakage with various porcelain surface treat-ments. Dent Mater 1991;7:118-123.Derand T. Stress analysis of cemented or resin-bondedloaded porcelain inlays. Dent Mater 1991;7:21-24.Anusavice KJ, Hojjatie B, Tensile stress in glass-ceramiccrowns: Effect of flaws and cement voids. Int J Prosthodont1992;5:351-358.Malament KA, Grossman DG. Bonded vs. non-bondedDicor crowns: Four-year report [abstract 1720]. j Dent Res1992;71:321.Grossman DG, Beckwith VR, Smith DK, Malament KA. Theuse of Hazard Analysis for ongoing clinical trials, j Dent Res1992;71:321.Yen T-W, Blackman RB, Baez R|. Effect of acid etching onthe f lexural strength of a feldspathic porcelain and acastable glass-ceramic. J Prosthet Dent 1993;70:224-233.

Volume 9, Number 4, 1996 353 The International Joumal of Prosthodontics

Prosllioclonlirs and Dental Technology

123. Grunder U, Strub |R. Implant-supported suprastructure de-sign. Int) Periodont Rest Dent 1990;10:19-39.

124. Neeser S. Esthetic solutions for fixed partial restorations withosseointegrated implants. Quintessence Dent Tech 1993:9-15.

125. Duncan )D, Swift E Jr. Use of lissue-tinted porcelain to re-store soft-tissue defects. J Prosthod 1994;3:59-61.

126. Clark EB. An analysis of tooth color. | Am Dent Assoc 1933;18:2093-2103.

127. Sproull RC. Color matching in dentistry. Part I. The three-dimensional nature of color. ) Prosthet Dent 1973;29:416-424,

128. Preston JD. The elements of esthetics' application of colorscience. In : McLean ]W (ed). Dental C e r a m i c s -Proceedings of the First International Symposium onCeramics. Chicago: Quintessence, 1983:491-520.

129. Ishikawa-Nagai S, Sato R, Furukawa K. Using a computercolor matching system in color reproduction of porcelainrestorations. Int) Prosthodont 1992;5:495-502.

130. Monsenego C, Burdairon G, Clerjaud B. Fluorescence ofdental porcelain. ) Prosthet Dent 1993;69:106-113.

131. Riley EJ, Filipancic JM. Ceramic shade determination:Current technique for a direct approach. Int ) Prosthodont1989;2:131-137.

132. Groh CL, O'Brien W), Boenke KM. Differences in color he-tween fired porcelain and shade guides. Int J Prosthodont1992:5:510-514.

133. Sproull RC. Color matching in dentistry. Part II, Practical ap-plications of the organization of color. ) Prosthet Dent1973;29:556-566.

134. What I Believe—Bartlette's Book of Familiar Quotations, ed9. 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 osseointegration initially mandated that when an implant fails to osseointe-grate, the implant must be removed and a 1-year healing period musí transpire beforeplacement of a second implant into the same location. More recently, numerous studieshave 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 regenerationas indicated. Therefore, the question arose as to whether the surgical techniques successfulwith tooth extraction sites can be applied to the sites of failed implants. This clincal reportdescribes 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 wereexposed, healing abutments were placed, and prosthodontic treatment was initiated. All fivepatients were followed for a minimum of 3 years. During this time, all implants successfullymaintained osseointegration and exhibited less than 1 mm of overall crestal bone loss. Theauthors conciuded that a 1-year healing period after implant removal may not be necessaryprovided 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 sufficientbone remains for the replacement procedures. While the findings of this limited clinical re-port must be considered preliminary, the implant replacement procedures described meritadditional 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

The International lournal of Prosthodontics 354 Volume9, Number 4, 1996