Artificial Crowns andFixed Partial Dentures

18 to 23 Years AfterPlacement

Sigvjrd Palmqvisl, DDS, PhD

Barbro Swarlí, DDS

Department of ProstheticsPostgraduale Dentil Education CenterOrebro, Sweden

Patients receiving artificial crowns and fixed parfial denturesat a prosthodontic clinic were examined 18 to 23 years aftertreatment. The long-term results were good, especially forthe metal ceramic restorations: 79% remained unchangedand only 3% had been removed. The success rate for thegold-resin restorations vwas less favorable: 43% remainedunchanged and 33% had been removed. The use of onecantilever extension unit had not negatively influenced theresults for the fixed partial dentures. Generally, thoseabutment teeth fhat had been removed during theobservation period had received previous endodontictreatment before restorations had been placed. Endodonticcomplications on abutment teeth were more frequent in themandible than in the maxillae. Intj Prosthodont 1993:6:279-285.

T here are various reports on the success andfailure of fixed prosthodontic restorations. The

reports can be classified according fo the type ofstudy and patients involved as follows;

1. Studies based on patients witb failed unitspresenting to dental scbools or prostbodonticclinics'"^

2. Studies of groups of patients treated at dentalschools'"'

3. Follow-up studies of special prostbodontic res-torations and/or treatment performed by dentalspecialists'""

4. Fpidemiologic studies of randomly sampledsubjects''"-'

The results are divergent and long-term resultsare infrequently reported. It appears tbat the fail-ure rates per year for fixed partial dentures (FPDs)are not stable, increasing affer some period of

Reprint requests: Dr Sigvard Palmqvist, Department of Pros-

thetics, Postgraduate Education Center, FO Box 1126, S-701 U

Orebro, Sweden.

service,'-' Cantilever FPDs seem to form a specialrisk group for general practitioners," ""•"•-'

The purpose of this study was to evaluate thelongevity of certain fixed prosthodontic restora-tions (artificial crowns and FPDs of af least fiveunits) placed in a prosthodontic clinic during theyears 1968 to 1973. The patients were examined in1991 and 1992,18 to 23 years affer the cementationof the fixed prostheses.

Materials and Methods

Patients who had received crowns and/or FPDsbetween 1968 and 1973 at the Department of Pros-thetics of the Public Dental Service in Orebro,Sweden, were traced through official registers.Tbose who were found in the registers and met theinclusion criterion were offered a complimentaryfollow-up examination.

The inclusion criterion required the patient tohave an extension of tbe fixed restoration of at leasffive units. Arches witb a combination of fixed andremovable dentures were excluded. Arches witbspecial prosthodontic solutions, such as fixed pros-theses receiving some of tbeir support from tbe

, NumberÍ,1993 279 The Inlernalior I of Pro5thodontic5

Artificial Crowns and Fixed Partial Dentures Palmqviîl/Swartz

Table 1 Distribution ot Subjects Treated From 1968 to 1973

Gender Age distnbution

Treated from 1968 to 1973Reported deoeased or not

found in official registersMoved trom the area and/or

not availabie for examinationExamined trom 1991 to 1992

Men

5518

14

23

Women

6713

11

43

Totai

12231

25

66

s 2 9years

297

8

14

30 to 49years

509

12

29

years

4315

5

23

residual ridge ("saddle bridges")," were also ex-cluded. The number of subjects meeting the inclu-sion criterion, as well as the numbers of subjectsexamined and tbose who could not be examinedfor various reasons, are sbown in Table 1. The sub-jects are grouped according to their age at thecompletion of their original treatment.

The present Department of Prosthetics at thePostgraduate Dental Education Center in Orebrooriginated in 1%8 as the Department of Prostheticsof tbe Public Dental Service, Two specialists were inservice there during the years from 196S to 1973,There were also dentists in service at the depart-ment who were following the education programfor a Board Certificate in periodontics, (In Sweden1 year half-time service at a prosthodontic clinicis required for a Board Certificate in periodontics,)The routine procedures at the Department of Pros-thetics included a posttreatment examination anddocumentation of all FPD patients with photo-graphs, diagnostic casts, periodontal records, andradiographs of all teeth involved in tbe prostbodon-fic treatment. These records were used for compar-ison with the findings at the recall examination.

All patients treated had been referred to theDepartment of Prosthetics from eitber generalpractitioners or other specialty clinics. Every pa-tient had a general practitioner who assumed re-sponsibility for the patient's regular dental servicefollowing the prosthodontic treatment. The pa-tients were then examined at the Department ofProsthetics after 1 year and in most instances werenot seen again after this time, although certainpatients were followed irregularly after more than 5years. For example, some patients baving complica-tions received a new referral to the Department ofProsthetics for examination and furtber treatment.

From the posttreatment records, the followinginformation was used :

1, Age and gender of patient2. Main diagnosis for prostbodontic treatment,

such as periodontal disease (all patients referred

from tbe periodontal department), cleft lip and/or palate, dental aplasia, severe malocclusion,enamel defects, attrition, or trauma

3, Other risk factors, such as bruxism, bigh cariesactivity, or psycbosocial problems

4, Numbers and types of single crowns (gold, gold-resin, metal ceramic)

5, Numbers and types of FPDs (gold-resin, metalceramic)

6, Numbers and types of abutments (intermediateor terminal abutment witb 0, 1, or 2 cantileverunits; vital or endodontically treated abutments)

7, Numbers and types of retainers in tbe variouspositions (complete gold crown, complete gold-resin crown, complete metal ceramic crown,partial pin-retained crown)

For the prostheses, maxillaryor mandibular posi-tion was registered. Presence of endodonticallytreated teeth with separated roots was also noted.

Complete intraoral radiograpbs were made at thefollow-up examination, Tbe clinical examinationswere performed jointly by botb authors. In theevent of disagreement, the decision was made bytbe one autbor (B.S,) who bad not been involved Inthe treatment of the patients from in 1968 to 1973.

From the clinical examinations and the radio-graphs, the following data were recorded:

1, For single crowns, the numbers and types ofcrowns remaining and those removed

2, For FPDs, the numbers and types of those re-maining unchanged, remaining but repaired,partly remaining, or removed

3, For retainers, tbe numbers and types of retain-ers in function (remaining retained) and thosenot in function (removed or unretained).

4, For abutments, the numbers and types of abut-ment teeth remaining and those removed

For the FPDs that had been removed, the rea-son(s) for removal were noted : caries, loss of reten-tion, impaired estbetics, fracture of framework, lost

The Inrernalional lournal of Proslhodontics 280 Volume 6, Nui

ArtificiEll Crowns and Fixed Partial Dentun

Table 2 status of Fixed Partial Dentures at the Follow-up Examination; DistributionAccording to Material Type and to Cantilever Extension

Status

Remainingunebanged

Remainingbut repaired

Partlyremaining

Removed

Materiai type (%)

Gold-res in

(n = 69)

43

12

12

33

fvletalceramic(n = 34)

79

6

12

3

Cantilever extension (%)

Nocantileverextension(n = 69)

58

7

12

23

One-unitcantileverextension(n = 24)

58

17

4

21

Two-unitcantileverextension(n - 10]

30

10

30

30

Alltypes

(n = 103)

55

10

12

23

abutment(s), or need for extended treatment. Forthose abutment teeth that had been removed, themain reason(s) for removal were also noted : caries,periodontal disease, fracture, résorption, other, orunknown. The reasons were noted from patientrecords, information given by the general practi-tioners who had served the patients, or, in a fewinstances, from direct interrogation of the patients.

The present status of abutment teeth that hadbeen vitai at the posttreatment examination wereevaluated as either vital (no visible periapicalchange on the radiographs) or nonvital (endodonti-cally treated and/or showing a periapical lesion onthe radiographs). Endodontic treatment through aretainer was not considered as a repair of the FPD.

Other findings also noted included impaired es-thetics resulting from wear, color change or frac-ture of veneer material, occlusal discrepancies, cra-niomandibular disorders, and restorations placedon abutment tooth margins (not regarded asrepairs).

The significance of differences between groups

was evaluated by means of the chi-square test-

Results

A total of25 single crowns had been piaced in thepatient population; there were 6 gold crowns, 3gold-resin crowns, and 16 metal ceramic crowns.All of these except for two gold crowns were re-maining at the follow-up examination (92%).

A total of 103 FPDs were placed; 69 were gold-resin and 34 metal ceramic. At the follow-up exami-nation, 77% of the FPDs either remained un-changed, remained but had been repaired, or werepartially remaining (Table 2)- In most instances, arepair had been necessitated by wear or fracture ofthe veneer material, "Partially remaining" most fre-quently meant shortening of the FPD because ofthe loss of a terminal abutment tooth. Of the gold-

Table 3 Numbers and Percentages of Retainers inFunction and Not in Function at the Follow-upExamination; Distribution According to Type of Retainer

Type of retainer

Gold crownGold-resin crownMetal ceramic crownPartial crown

All types

In function

n

41153122

34

350

%

61629576

72

Notin function

n

26946

11

137

393ab

24

28

resin FPDs, 33% had been removed as compared toonly 3% of the metal ceramic FPDs (P < .001).

In those patients aged under 29 years, B0% of theFPDs remained unchanged, compared to 44% ofthose placed in patients aged 30 to 49 years and 61 %of those in patients older than 50 years. The differ-ence between the first age groups was significant (f< .01). No significant differences were noted forthe status of the FPDs in relation to the followingvariables: gender of patient; main diagnosis beforetreatment; special risk factors noted; presence ofcantilever extension; or placement in the maxillaeor mandible.

The sample was composed of 487 retainers placedfrom 1968 fo 1973. The status for those retainers atthe follow-up examination is shown according todistribution by type of retainer (Table 3) and positionof retainer (Table 4). It was found that 95% of theretainers remained in function for the metal ceramiccrowns, compared to 64% for the other types ofretainers combined {P < .001). For the partial pin-retained crowns, it should be noted that the per-centage of those in function was strongly influencedby fhe low number of such retainers and the fact thatseven of fhem had been removed from one patient.

ymefe, Number 3,1993 281

Arlificiai Crowns and Fiied Partial Denlu Paimqvist/Swartï

If this patient is excluded, 89% of partial pin-retained crowns remained in function. No signifi-cant difference was found related lo position ofretainer, but there was a tendency toward higherfailure rates for terminal abutments as compared tointermediate abutments.

Of the 487 retainers, 365 had been placed on vital

Table 4 Numbers and Percentages of Retainers inFunction and Not in Function at the Follow-upExamination; Distribution According to Position ofRetainer

Position of retainer

Intermediate abutmentTerminal abutment, no

cantiiever extensionTerminal abutment, one-un it

cantiiever extensionTerminal abutment, two-un it

cantiiever extension

Ali positions

In function

n

205118

20

7

350

%

7372

65

64

72

Notir function

n

7646

11

4

137

27?8

28

abutment teeth and 122 on endodontically treatedteeth. The percentages of retainers in function was74% for those placed on vital abutments and 66%for those placed on endodontically treated abut-ments. However, the difference was not statisticallysignificant. Only five retainers were placed onteeth having separated roots.

Sixty-seven abutment teeth (14%) had been re-moved during the observation period. The distribu-tion of those abutments according to position inthe FPD and to the endodontic diagnosis at theposttreatment examination is given in Table 5, Asshown, 10% of the vital abutment teeth had beenremoved, compared to 24% of the endodonticallytreated abutment teeth (P < .001), It should benoted thai seven teeth had been removed in onepatient on a psychiatric indication: diffuse pain thatIhe patient referred to the maxillary teeth, althoughthere was no dental indication for tooth removal.Another patient had all teeth removed as a result ofperiodontal disease and wore complete removabledentures at the follow-up examination. For thesame reason, another had the maxillary teeth re-moved and a complete denture placed. If these

Table 5 Numbers and Percentages of Removed Abutment Teeth; DistributionAccording to Position in the FPD and to the Endodontic Diagnosis al fhePosttreatment Examination

Position of abutment

Intermediate abutmentTerminai abutment, no

cantilever extensionTerminai abutment, one-unit

cantiiever extensionTerminal abutment, two-unit

cantiiever e ¡den s i on

Ail positions

Vital abutments

Totalnumber

213126

18

8

365

No,removed

2113

3

1

3B

%removed

1010

17

13

10

Endodontically treated

Totalnumber

6838

13

3

122

No,removed

1211

5

1

29

%removed

1829

38

33

24

Table 6 Diagnoses at fhe Follow-up Examination forRemaining Abutment Teeth That Had Been Judged asVital at fhe Posttreafmenf Examination; DistribufionAccording fo Type of Retainer*

Type of retainer No. vüa\ Mo. nonvital % nonvital

Gold crownGo Id-res in crownMetal ceramic crownPartial crown

291199139

Ail types

•Teeth were considerea nonvitai if they had bean endodonticaily treatedor showed a periapical lesion or ttie radiograpiis

Table 7 Main Reasons for Repair and Partial or TotalRemoval of FPDs; Numbers of FPDs in fhe DifferentCategories

f̂ iain reasonsfor changed conditions'

Partially TofailyRepaired removed removed

CariesLoss of retentionFracture of frameworkLoss of abutment tooth/teethImpaired estheticsNeed tor expanded treatmentOther or unknown

0103700

0127002

161

12331

"In a few ¡nslarces more than one reason was listea.

Ttie irternationai Jojrrial of Prosttiodonlics 282

PalmqvistíSwart! Artificial Crowns and Fi>ed Partiai Ocntur.

three patients who had all teeth removed in one orboth arches are excluded, the percentage of re-moved abutment teeth could be calculated at 9%instead of 14%.

There were higher figures for removal of terminalabutments compared to intermediate abutments. Ifthe three patients mentioned above are excluded,the difference is significant {P < .01]; 6% of theintermediate abutments had been removed, ascompared to 13% of the terminal abutments.

Of the abutment teeth that had been consideredvital at the posttreatment examination, 327 re-mained. At the foilow-up examination, 15% ofthose had received endodontic treatment or had aperiapical radiolucency (Table 6]. Fewer abutmentteeth ¡10%] that had received metal ceramic crownsbecame nonvital. The metal ceramic group differedfrom the groups with gold crowns and gold-resincrowns combined {P < .05]. The incidence of ini-tially vital mandibularabutment teeth that had beenendodontically treated or showed a periapical le-sion was 23%, compared to 11% for those in themaxillae (?< .01).

The main reasons for repair of the FPDs and fortheir partial or total removal are shown in Table 7.The patient who had a FPD removed together withseven abutment teeth on a psychiatric indication islisted under "loss of abutment tooth/teeth." An-other patient, who had two FPDs removed for thereasons "loss of retention" and "loss of abutmenttooth/teeth" had a severe alcohol abuse problemand had discontinued regular dental care. Thispatient had received seven partial pin-retainedcrowns.

The main reasons for removal of the 67 abutmentteeth were caries 110 abutment teeth], periodontaldisease (28 abutment teeth], tooth fracture (9 abut-ment teeth), and other or unknown reasons (20abutment teeth). Periodontal disease was the rea-son given for extraction of 19 abutment teeth in twopatients.

Discussion

The present study should be looked upon asmore than a retrospective study, since the post-treatment records were meant to be a baselineregistration for follow-up studies. The high per-centage of subjects not examined in the follow-upstudy seems acceptable, considering the amount oftime that had passed following fhe placement of therestorations. A number of those persons not foundin official registers are probably still alive but can-not be traced because the present civil registrationnumber system was not in use in dentistry at the

time they received their prosthodontic treatment.Considering the long observation period, at least 18years, no further classification was made of thecrowns and FPDs by length of service. There was nosignificanf change in the distribution of varioustypes of restorations during the period from 1968to 1973.

The long-term results presented here are compa-rable to most of those reported from studies withshorter observation periods. This is encouraging,especially as the failure rates per year in othermaterials have been shown to increase over alonger period of time.'^^ The results are also en-couraging, as technical and psychological treat-ment problems, together with the severity of thedisease, form the major reasons for referring apatient to a specialty clinic.

The most striking result was the higher successrate for metal ceramic FPDs compared to gold-resinrestorations. A similar long-term result has notbeen reported earlier. The reasons for choosingone or the other veneer alternative were not re-corded during the original treatment period. Onemight suspect that the choice of a more expensivealternative la metal ceramic FPDI was an expressionof a positive evaluation of the prognosis for therestoration. There were also some differences be-tween operators in their choice of material. (Mostof the metal ceramic FPDs were constructed by theauthor S.P.) However, none of these circumstancescan explain the poorer esthetic outcome for theresin veneers. While most of the metal ceramiccrowns and pontics were esthetically very satisfac-tory at the follow-up examination, a large numberof the remaining resin veneers were apparentlyworn and discolored. Subjectively to the authors,there were great differences in favor of the metalceramic constructions.

The highest percentage of retainers in functionwas also noted for the metal ceramic crowns. Thefailure of one restoration greatly influenced thepercentage of retainers in function in regard to thepartial pin-retained crowns. When this patient isexcluded, 89% of partial crown retainers remainedin function. Most of these were so-called PNP-crowns with both parallel and nonparallel pins,described elsewhere.™

The use of one cantilever extension unit did notgive a significantly higher failure rate for the FPDs.Tbis is not in accordance with the findings fromrandomly sampled materials in Sweden.-"-' Itshould be noted that there were only a few patientsin whom two cantilever units had been used. In-stead, periodontally weak terminal abutments hadsometimes been included in the restorations.

283 The International lournal ot Prosthodontics

Artificial Crowns and Fixed Pirtial Dentures

These abutments will be studied furtber by measur-ing changes in radiographie marginal bone levels.

The percentages of retainers in function were notsignificantly different for vital and endodonticallytreated abutment teetb. This indicates tbat an end-odontically treated abutment need not be regardedas a substantially increased risk. However, endo-dontically treated teeth dominated among theabutment feeth that had been removed during theobservation period. The higher percentages for re-moved terminal abutments should also be noted.The use of the endodontically treated distal abut-ment tooth has been shown to be problematic.-" Inthe present material, the highest percentage ofremoved abutment teeth was noted for endodonti-cally treated terminal abutments with one canti-lever extension.

Endodontic complications were noted for 15% oftbe remaining abutment teeth tbat had originallybeen classified as vital. These teefh had either beenendodontically treated during tbe observation pe-riod or had a periapical radiolucency at the follow-up examination. The percentage of complicationsafter 18 to 23 years (15%) should be compared totbat reported by Karlsson" after 10 years (11%).Bergenholtz and Nyman^ reported 15% pulpal ne-crosis after an average observation period of 8.7years in initially vital but periodontally weakenedteeth used as abutments for extensive fixed restora-tions, including two or more cantilever units. Evenhigher percentages of endodontic complicationshave been reported in extreme situations witb 12-unit FPDs on only two abutments. '•• " In the presentstudy, tbere was a significantly higher percentageof endodontic complications in mandibular abut-ment teetb (23%) as compared to the maxillaryabutment teeth (11%].

Caries was not a major problem in this study. Thisis not in agreement with some earlier reports,'"™but supports tbe results by Valderhaug' andKarlsson.^' The view beld by Karlsson that caries isoften secondary to loss of retention, not the oppo-site, is shared by the authors. In this study, a num-ber of marginal restorations on abutment teethwere noted but seemed not to have affected thelong-term results for the fixed restorations. Whenevaluating the caries risk it should be remembered,however, fhaf mosf of fhe patients in the study hadreceived regular dental care.

Fixed partial dentures are initially expensive. Tcjudge from the present study, however, it seemsreasonable to calculate a life span of abouf 20 yearsfor a FPD, provided that proper materials and tech-niques are used. Moreover, in the study populationadditional treatment for maintenance during the

follow-up period was usually not extensive. Thismeans that the average cost for a FPD per year overa 20-year period can be expected to be fairly low.From a political/economic point of view tbis mustbe of great importance. High initial costs but lowmaintenance costs for FPDs should be compared totbe total costs for removable partial dentures[RPDs] over the same period of time. The treatmentamount necessary tor maintenance of initially less-expensive RPDs has been reported to be consider-able over a 10-year fol iow-up period," but the issueneeds further sfudy.

In the present study, there was a higher failurerate for patients aged 30 to 49 years compared tothose in younger age groups. Even in comparisonto those aged over 50 years the figures were unfa-vorable, although the difference was not signifi-cant. This is somewhat contradictory to a report byKarlsson,-' who noted poorer results for the oldestage groups. Fiowever, we find fhe frend in ourmaterial logical, as an early onsef of dental diseases(resulting in a need for fixed prosthodontics at earlyages) certainly is not favorable for tbe prognosis.

Conclusion

An investigation of patients treated with crownsand FPDs at a prostbodontic clinic from 18 to 23years ago reported good long-term results, espe-cially for the metal ceramic restorations: 79% re-mained unrepaired and only 3% had been com-pletely removed. The results for the gold-resinFPDs were less favorable: 43% remained un-changed and 33% had been removed. The use ofone cantilever extension unit had no significantinfluence on the long-term results. Endodonticallytreated abutment teeth did not, per se, seem toconstitute a substantially increased risk for retainerfailure, but the teeth removed during the observa-tion period were predominately endodonticallytreated. Endodontic complications were more fre-quent in mandibular abutment teeth than in thosein the maxillae.

References

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3, Foster LV. Faiied conventional bridge work from generaldental practice: Clinical aspects and treatment needs of 142cases. Br Dent 11990; 168:199-201.

4, Backlund N, Akesson :'̂ A. Efterundersokning av kron- ochbroarbeten. Odontol Rev 1957,-3:121-133.

The International loiirnal of Prosthodontics 284

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Karlstrom S. Efterkontroll av brofail framstallda eniigt dens,k, Pontostfuctor-metodiken, Svensk Tandlakar-Tidskrifi1960; 53:957-972,

Nyman S, Lindhe |. A longitudinal study of combined peri-odonlal and prosthetic treatment of patients with advancedperiodontal disease. | Periodontol 1979;50:163-169.Palmqvist S, Allard U. Brofail med partiella PNP-kronor.Tandlakartidningen 1980;72:477-481.Coonaert ), Adriaens P, De Boever|. tong-term clinical studyof porcelain-fused-to-gold restorations, I Prosthel Dent1984;51:33B-342.Reuter )E, Brose MO. Faiiures in full crown retained denialbridges. Br Dent 11964; 157:61-63.

Isikowitz L. A long-term prognosis tor frpe-end saddle-hridge. J Oral Rehabil 1985,12:247-262,Carlson BL, Yontchev E, Carlsson CE. Extensive fixed partialdentures on mandibular canine leeth: A 5-year recall study.Inl I Prosthodont 19a9;2:26S-271.Bergman B, Bessing C, Ericson G, Lundquist P, Nilson H,Andersson M, A 2-year follow-up study ot titanium crowns.Acta Odontol Scand 1990;4e:113-117,

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18, Clanlz P-O, Ryhe C, lendresen MD, Niiner K, Quality ofexteniive fixed prosthodontics after five years, J ProslhetDent1984;52:475-479.

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20, Randow K, Glantz P-O, Zoger B. Technical failures and somerelated clinical complications in extensive tixed prosthodon-tics. An epidemiological study of long-term-clmical quality.Acta Odontol Scand 1986; 44:241-255.

21, Karlsson S. Faiiures and iength of service in fixed prostho-dontics after iong-term function, Swed Dent ) 1989;13:185-192,

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íiíeíalure Abstracts

Selection of the Proper Margin Conf igtjralion

The primary function of any prosthetic crown restoration is ihe preservation of the tooth and itsadjacent tissues. The margin configuration of the prepared tooth, location of the margin relative to thegingival crevice, and Iahoratory handling of the restoration are critical factors in achieving this primaryfunction. This study reviewed popular metal ceramic margin designs and deiineated the clinicalconditions in which they are most appropriate. The rhamfer margin configuration is inappropriate formetal ceramics in areas of porcelain appiication. Insufficient stability of the metal framework duringporcelain firing results in distortion and a lack of precise marginal fit. The shoulder margin designprepared to a 90-degree angle, when restored with an all-porcelain margin, can produce idealesthetics, surface finish, and biocompatibility, Ihe slanted shoulder margin configuration, prepared ata 60- to 75-degree siant, is typically restored with a gold-porceiain margin. The iaboratory technique(ie, the "disappearing margin") invoives the precise convergence of the metal, opaque, and bodyporcelains at the margin terminus. The resulting marginal fit, finish, and esthetics may hequestionable. The shoulder bevel marginal configuration is restored with a metal collar that providesgood marginal stability during porceiain firing, if esthetics are crucial, the shouider bevel preparationshould be avoided. The knife-edge margin is useful only at times of furcation invasion and should beavoided during metal ceramic crown fabrication. In general, crown preparation should not be initiatedin the absence of adequate and healthy gingival tissues. After piacrng margins with diamond rotaryinstrumentation, finishing with hand-held instruments will aid in achieving an optimally precise fit oftbe final restorafion,

Wright WE./ Ca/Denr,̂ ssoc 1992; 20:41-44, Rtferences: 14, Reprints: Dr Wright, .S15 E Micheltorena St, Ste C, SantaBarbara, CA 93103. — Dawrf tt Cagna, OMD. Department oí Proitbodonuçs, The University ai Teias Health ScienceCenter at San Antonio, San Antonio, Texas

285 The International Jourrai of Prosthodontics