Peíef S. Lund, DDS, MSAssistant Professor

Shear Bond Strength ofTextured Opaque Porcelain

Phillip W. Davis, BSDenlat Sludenl

Department oí ProstiiodonticsColiege of DentistryUniversity oí ItjwaIowa City, Iowa 52242

Textured opaque porcelains have been introduced toimprove the appearance of metal ceramic restorations byincreasing light refraction. This investigation compared theshear bond strength of a textured opaque porcelain withthat of a conventional opaque porcelain. Opaque and bodyporcelains were fired onto six different alloys and thespecimens were loaded to failure by applying shear force atthe alloy-porcelain interface. No significant differences inbond strength were found between the textured andconventional opaque porcelains for any of the alloys tested.Int I Prosthodont 1992; 5:503-509.

T he appearance of metal ceramic restorations issometimes less than optimum because the

reflective surface of the opaque is visible beneaththe body porcelain. To overcome this problem, anopaque porcelain (Ceramco II Ultra-Pake, Cer-amco Inc, Burlington, NJ) was introduced. Crys-talline inclusions in the opaque porcelain layerreportedly cause light refraction (see Fig 1).

The appearance and color of metal ceramicspecimens fabricated using the textured opaqueporcelain have been evaltjated,' However, clini-cally important factors such as metal ceramicadherence, porcelain-alloy and porcelain-porce-lain thermal compatibility, physical properties, andresistance to oral degradation^ have not beenreported.

The purpose of this investigation was to comparethe shear bond strength of the textured opaqueporcelain and a conventional opaque porcelain(Ceramco II Paint-O-Pake¡ when fired on six typesof alloys for ceramic bonding.

Materials and Methods

A planar shear test was used to compare bondstrengths of the textured and smooth surfaceopaque porcelains. The porcelains were fired to sixalloys used in metal ceramic restorations (Table 1),A 3-mm thick addition of body porcelain was sub-sequently applied. Specimens were loaded to fail-ure by applying a shear force to the porcelain atthe alloy-porcelain interface.

Table 1 Alloys Used for Metal Ceramic BondStrength Testing

Alloy type

Higli Au

Aj-PdHigti pa-CoPd-AgNi-CrCo-Cr

Alloy name

Jelenko ' C"t

ClympiatPTM-88tJelstarfTalladium PJGenesis l i t

Composition(major ele

87.5 Au, 4.5% Pt,1.0% Ag

51.5% Au, 38.5%88% Pd60% Pd, 28% Ag74.0% Ni, 13,5%53% Co, 27% Cr,

3% Hu

mentsi"

. 6.0% Pd,

Pd

, 6% InCr, 5.0% Mo10% W,

Presented at the ¡991 annual session of the American Asso-ciation for Dental Research. Boston, Massachusetts.

"As given By the manijtactjrers.tJelenko üsrtai Health Products, Armonk, NY.}Tallsdium Inc, Valencia, Calit.

Volume 5, Number 6, 1992 503 The International lournal of Prosthodonti«

Shear Bond StrenElh o¡ Textured Opaque Porcelain

Substrates were cast using six alloys used inmetal ceramic restorations (see Table 1). Sprueformers were attached to the ends of rectangularplastic patterns 6.0 X 6.5 X 10.0 mm. The patternswere arranged concentrically in casting rings, fourpatterns per ring, and invested in a carbon-freephosphate-bonded investment (High Span II,lelenko Dental Health Products, Armonk, NY)using 5.0 mL distilled water with 5.5 mL investmentliquid for each 60 g of powder. Patterns were elim-inated in a burnout furnace (Hi-Therm. JelenkoDental Health Products] following each alloy man-ufacturer's recommendations. A centrifugal castingmachine (Centrifico, Kerr Manufacturing Co,Romulus, Mich) and multiorifice gas-oxygen torch(Harris Model 16 Calorific, Cleveland, Ohio) wereused for casting. New alloys were used to make allcastings. New carbon-free crucibles were used foreach alloy and all procedures followed manufac-turers' recommendations.

Castings were devested, air abraded with 50-;imaluminum oxide (Brazilian Red-Brown AluminumOxide, Talladium Inc, Valencia, Calif), and thesprues were removed. No chemical investment-removal agent was used. One half of the end ofeach casting (3.0 X 6.5 mm) was finished for por-celain application by roughening with a medium-grit cylindrical slow-speed diamond Instrument (T-2 Diamond, Talladium Inc). A new diamond burwas used for each alloy. Completed castings weresteam cleaned and oxidized for porcelain appli-cation following each alloy manufacturer's instruc-tions. Air abrading with aluminum oxide followingoxidation is specified by the manufacturer for threeof the alloys (Au-Pd, high Pd-Co, Co-Cr), while forthe other alloys, no recommendation is made. Foruniformity, all castings were again air abraded withaluminum oxide after oxidation and steam cleaned.

Specimens of each alloy were arbitrarily assignedinto two groups. Each opaque porcelain wasapplied to eight specimens of each alloy followingfiring cycles recommended by the porcelain man-ufacturer (Table 2). The manufacturer of the Ni-Cralloy recommends an elevated firing temperaturefor the initial opaque layer and that subsequentfirings follow the porcelain manufacturer's guide-lines. Therefore, each opaque porcelain wasapplied to eight additional Ni-Cr alloy specimensand the initial opaque layer was fired following thatalloy manufacturer's recommendations (see Table2).

The opaque porcelains were applied to the 3.0X 6.5-mm prepared area on each substrate. Exper-imental samples received Ultra-Pake texturedopaque porcelain, shade A2. A base layer of pre-

Lund/Dav

Pake

64933

7267

988/952-932t

1010/974-954t

0

Ultra-Pake

5003372

200101Q/975-

975t1010/975-

975t45 vacuum

45 air

Table 2 Opaque Porcelain Firing Cycles

Paini-O-

Idle temp (°C)Drying time (min)Entry time (min)Vacuum (om Hg)Heating rate (°C/min)Vacuum release-1st firing (°C)Vacuum release—2nd firing ¡°C¡High temp-ist firing ("C)High temp-2nd tiring (°C)High temp hold (s)

•Ni-Cr elevated temperature grojp/Ni-Cr standard terrperature groupanO aii other alloys.

tAII groJps identical.

mixed opaque porcelain paste was applied usinga brush. The manufacturer specifies a single colorfor all shades. The refractive crystals were sprinkledonto the wet opaque surface. Specimens wereinverted and gently agitated to remove excess crys-tals not adhering to the wet surface. The manu-facturer supplies the refractive crystals in threecolors, designated "light," "medium," and "dark."Medium-colored crystals are specified for the baseopaque layer for shade A2, The first opaque layerwas fired (see Table 2) and allowed to cool. A sec-ond layer of opaque porcelain was applied andfired (see Table 2) in a similar manner. For thesecond layer a colored paste is supplied for eachshade, however light-colored crystals are specifiedfor all shades.

Paint-O-Pake conventional opaque porcelain,shade A2, was applied to the prepared area of thecontrol specimens. The opaque porcelain wasmixed with its recommended liquid (CeramcoOpaque Modeling Liquid) and applied with abrush. A thin first layer was applied and fired, fol-lowed by a second layer that masked the metalcolor (see Table 2).

Both the textured and conventional opaque por-celains were applied according to the manufac-turer's instructions. The final thickness for eachopaque porcelain was the minimum necessary tovisually mask the alloy color completely. No futiherattempt was made to control or measure the thick-ness of either porcelain. The fired opaque porce-lains are illustrated in Fig Î .

Body porcelain (Ceramco II Body. Shade A2) wasapplied over the opaque layer on each specimento a thickness of 3 mm (Fig 2). Specimens wereplaced in a silicone mold to shape the porcelain.Mold dimensions were slightly oversized to allowfor porcelain shrinkage to the 3.0 X 6.5-mmopaqued area. Body porcelain was mixed with its

The International ;ournal oí Prosttiodonlicí 504 •5, Number 6, T992

Lund/Oa Shear Bond Strength of Textured Opaque Porcelain

Rg 1 (Above) The opaque porcelains fired to alloy sub-strates for metal ceramic shear bond strength testing, (Leñ)Uitra-Pake textured opaque porcelain. (Right) Paint-O-Pakeconventional opaque porcelain.

Fig 2 (Right) Completed metal ceramic specimen. Top ofspecimen (lefty. Porcelain. Top of specimen (right). Resin. Bot-tom ol specimen: Ailoy substrate.

recommended liquid (Ceramco Body ModelingLiquid) and the slurry was added with a brush. Por-celain was condensed by blotting with a tissue andspecimens were removed from the mold. After aninitial firing, body porcelain was added to deficientareas and all specimens were refired. Following thecorrection firing, porcelain surfaces were airabraded using aluminum oxide, steam cleaned,and naturally glazed. All firing schedules followedthe manufacturers' recommendations.

A single porcelain furnace (jelcraft HT, jelenkoDental FHealth Products) was used for all alloy oxi-dation and porcelain firing cycles. All cycles foreach alloy group were completed consecutively.Before each group, furnace calibration was verifiedand the furnace muffle was decontaminafed. Anew carbon decontamination rod (De-con-tam, ]MNey Co, Bloomfield, Conn) was used for each alloygroup according to instructions.

Autopolymerizing resin was added to the end ofeach alloy specimen adjacent to the glazed por-celain and subsequently used to apply the shearload against the porcelain (see Fig 2). A separatingmedium (MS-122 Release Agent Dry Lubricant,Miller-Stephenson Chemical Co, Inc, Danbury,Conn) was applied to the exposed alloy surface toprevent adherence to the resin. Tape was wrappedaround each specimen to the height of the por-celain as a form for the resin. Poly (methyl meth-acrylate) resin (Clear Orthodontic Resin, LD CaulkCo, Div of Dentsply Int Inc, Milford, Del) wasmixed and poured into the recess. After setting,the resin was trimmed flat and flush with the sideofthe alloy substrate (see Fig 2). Specimens were

stored under ambient conditions until mechanicaltesting.

Specimens were loaded to failure on a mechan-ical testing machine (Model 1115, Instron Corp,Canton, Mass). A jig allowed positioning and heldspecimens in the machine. A flat metal plungervertically loaded the acrylic resin at the alloy-resininterface (Fig 3). The resin was loaded to distributethe force along the alloy-pnrcelain interface and

Fig 3 Planar shear testing configuration.(Center) fvietal ceramic specimen in posi-tioning jig. (From toß)Me\3.\ plunger of test-ing machine.

Volume 5, rJumber 6. 1992 505 The International lournai of Pros thod on lies

Shear Bond Strength of Textured Opaque Porcda Lund/Dav

Table 3 ObservedOpaque porcelain

Paint-O-PakeUltra-Pake

Metal Ceramic Failure PatternsHigh Au Au-Pû Pd

1 1 1III III III

Ptl-Ag

1III

Ni-Cr"

IIIV

Co-Cr

IIIV

Type I: Ciean alloy surface with a single, small fragment of opaque porcelain thick enough to mask the alloy.Type II: Essentiaiiy ciean alioy surface, however small areas have a taint frosty appaarance from minute amountsot retained opaque porceiain; Singie, smaii fragment ot opaque porcelain thick enough to mask the alloy.Type III: fulost of the alloy surface has a slightly trosty appearance from smaii amounts ot retaineû opaqueporceiain; Single, smaii fragment of opaque porcelain thick enough to mask the ailoy.Typs IV' fiíost of the alioy surface has a distinctly frosty appearance from small amounts of retained opaqueporcelain; Large or multiple opaque porcelain fragments thick enough to mask the alloy."High, and low-temperature groups identical

Table 4 Metal Ceramic Shear Bond Strengths

Alloy

Ni-Cr (higti)§High Pd-CoHigti AuPd-AgNi-Cr|iow)Co-CrAu-Pd

n

8878888

Mean(MPa)

16.815.413.913.613.513.313.3

Ultra Pake

SD

2.73.01.92.82.11.22.4

C V(%¡

16.11 9 513.720.615.6

9.018.0

Opaque porcelain

Duncan'sGroupt

AA,B

BBBBB

n

8888888

Mean(MPa)

14.715.514.213.515.515.313.7

Paint-0-Pake

SD

2.32.11.32.62.13.72.0

C V(%)

15.613.5

9.219.313.524.214.6

Duncan'sGroupt

AAAAAAA

Pt

0.120.950.750.990.090.180.71

'CoefPcient of variation,tMeans with the same letter are not significantly different (a = 0 05).4:Statistical probability determined by one-way analysis of variance between porcelains for each alloy.§Elevated temperature f rst opaque firing as recommended by the alloy manufacturer; all other porcelain firings as recommended by the porcelainmanufacturer.

decrease stress concentrations that might arisefrom any unevenness of contact between theplunger and tbe specimen. The load vector wasparallel to tbe alloy-resin and alloy-porcelain inter-faces. Dimensions of the plunger provided loadapplication 1 mm in width from the alloy-resininterface along the entire span of resin (see Fig 3).Samples were tested in an arbitrary order. The test-ing machine was allowed to warm up for 1 bourbefore use and was calibrated initially and againafter every 10 specimens. A 500-kg load cell wasused at a crossbead speed of 0.5 cm/min.

The load to cause porcelain bond failure, seenas a sharp peak on the chart recording of appliedload, was recorded for eacb specimen. Shear bondstrength (force/area) was calculated from tberecorded failure loads, assuming an adherence areaof 3.0 X 6.5 mm for all specimens. Analysis ofvariance (ANOVA) was used to identify significantdifferences in mean metai ceramic shear bond

Table 5 Full-Model Analysis ol Variance

Source of variation

M ode iMetalPorcelainMetal/porcelain/lnteraotion

Error

df

13616

97

sst

119.049470.8629

3.905044.2815

557,5538

F

1.592,050,681.28

P

.10

.07

.41

.27

'Degrees of freedom.tSum of squares.

strengtbs between groups. One specimen wasomitted from tbe analysis because data could notbe obtained from tbe cbart recorder.

Casual observation of alloy substrates after test-ing revealed differences in the amount of remain-ing porceiain. Therefore, specimens weresubsequently examined for differences in the pat-tern of porceiain faiiure. After regrotiping speci-mens according to ailoy type and opaque

nternationai Jcurnai of Prosthodontics 506 • 5, Number 6. 1992

Lund/Da Shear Bond Strength of Textured Opaque Porcelain

1•Fig 4 Metal ceramic failure patterns. Top (left to right): TypesI and II. Bonom (left to right): Types III and IV. See Table 5for description of types and the pattern observed for eachmetal ceramic group.

porcelain, a single investigator examined the alloysubstrates using unaided vision. Based upon theappearance of all specimens, a classificationscheme was devised (Table 3). Each alloy-porcelaingroup was classified into one of four categoriesbased upon the appearance of the bonding areasof all specimens in the group.

Results

Mean values for shear bond strength ranged from13.3 MPa, for Ultra-Pake textured opaque porce-lain with the Au-Pd and Co-Cr alloys, to 16.8 MPafor Ultra-Pake with the Ni-Cr alloy (Table 4). Full-model analysis of variance (Table 5) showed nosignificant differences in shear bond strength (a =0.05 significance level) attributable to the porcelain(P = .41), metal (P = .07) or their interaction (P= .27). Further, one-way ANOVA (see Table 4)showed no significant differences (a = 0.05 sig-nificance level) between opaque porcelains for anyof the alloys tested (P = .09 through .99).

Although the purpose of the investigation wasto compare opaque porcelains, data were analyzedfor differences between alloys for each opaqueporcelain. One-way ANOVA did identify a signif-icant difference in shear bond strength betweenalloys for Ultra-Pake porcelain (P = .04), but nosignificant differences for Paint-O-Pake (P = .47)were identified. For Ultra-Pake porcelain, Dun-can's multiple range tests (a = 0.05) revealed thatthe bond strength of the Ni-Cr alloy subjected tothe elevated firing schedule was significantly higherthan all other alloys with the exception of the highPd-Co alloy [see Table 4).

All specimens exhibited areas of cohesive failureat the a!!oy-porcelain interface, indicated by frag-ments of porcelain adhering lo the metai substrateafter testing. In addition, all specimens exhibitedareas assumed to be free of porcelain, as the colorof the exposed metal in these areas appeared thesame as the air-abraded specimens prior to por-celain application. These wore assumed to be areasof adhesive failure. All specimens within a groupexhibited nearly identical failure patterns, given inTable 3. Representative examples of each failurepattern are shown in Fig 4, In general, more opaqueporcelain, both in area and thickness, remained onUltra-Pake specimens ¡failure types III and IV) thanon Paint-O-Pake specimens (failure types I and II).For Ultra-Pake specimens, more opaque porcelainremained on the N'i-Cr and Co-Cr alloys (failuretype IV) than on Ihe other groups.

Discussion

In vitro metal ceramic bond strength tests allowcomparison of different materials under controlledconditions. Characteristics of an ideal test havebeen described in the dental literature:^'1. Tbe testing configuration induces adhesive

metal ceramic failure within the interfacialadherence zone, but not cohesive failurewithin the porcelain.

2. Specimen loading generates uniform stressdistribution along the alloy-porcelain inter-face, permitting accurate force/area bondstrength calculations.

3. Specimen or testing geometries do not createstress concentrations within the porcelain thatmay initiate failures below the true adhesivebond strength.

4. Specimen preparation and testing proceduresare uncomplicated, allowing evaluation ofmany metal ceramic pairs.

Numerous metal ceramic bond strengtb testshave been described, however none of tbem ful-fills all criteria of an ideal test.^' The rectangularplanar shear test used in the present study com-pares favorably with others evaluated in the dentalliterature. Previous studies examined stress distri-bution in 12 different metal ceramic bond strengthtesting configurations using finite element analy-sis.'^ The investigators compared uniformity ofstress distribution and presence of stress concen-tration areas along the alloy-porcelain interface, aswell as the likelihood of interfacial shear failurerather than tensile failure within porcelain.Although several of the test configurations ratedfavorably for one of these aspects, only the rec-

VolumeS, Number 6, 1992 507 I of Prosthodorti«

Shear Bond Strength of Tentuted Opaque Pgrcelarn

tangular planar shear and oblique shear testsranked high for all aspects. The oblique shear testresulted in the most ideal stress distribution,^ How-ever, specimen preparation and testing procedureappear complicated, and testing difficulties weredescribed.

Failures for all specimens were assumed to becombined adhesive-cohesive failures. It could bedefinitively concluded that areas of cohesive fail-ure existed because of clearly visible fragments ofporcelain remaining on the alloy surface after test-ing. However, it is possible that areas presumed tobe porcelain free were actually covered by a micro-scopic layer of porcelain, not detected by unaidedvisual examination. Further analysis using scanningelectron microscopy or surface compositionalanalysis would be necessary to rule out this pos-sibility.

Areas of cohesive failure observed in the presentstudy and also reported previously^ indicate thatthe planar shear test is not an ideal metal ceramicbond strength test. However, the observed failurepattern more truly represents failure modes com-monly seen intraorally. Failure patterns seen in thisstudy may be indicative of clinical failure modesfor the two opaque porcelains. Although the pat-tern of failure was different for the two porcelains,under the test conditions of this investigation theoverall strengths of the metal ceramic systems wereequal.

Areas of porcelam cohesive failure may resultfrom several factors. Cohesive failures could indi-cate that the strength of the metal ceramic bondexceeded the strength of the porcelain itself,resulting in predominantly cohesive porcelain fail-ures. What was actually observed were failuresassumed to be combined, having both adhesiveand cohesive components. Combined failures mayindicate the presence of residual stress concentra-tions in the porcelain at the areas of cohesive fail-ure. Any residual tensile stress within the porcelainwould decrease the external load necessary tocause fracture. Failure may have originated at areasof high stress within the porcelain or originated atthe alloy-porcelain interface and progressedthrough areas of high porcelain stress because ofincreased chance for fracture.

Porcelain cohesive failures may have alsoresulted from the method of loading. All specimensexhibited cohesive porcelain failure on the side ofloading immediately adjacent to the acrylic resin(see Fig 4). Specimens differed in the extent thatcohesive failure continued across the interface.The 1 -mm-wide plunger and the intervening resinprobably resulted in distributed loading, rather

Lund/Davis

than loading strictly at the alloy-porcelain interface.Previous analysis indicated that distributed loadingof a rectangular planar shear specimen results jnsignificant probability of porcelain tensile failurerather than interfacial adhesive failure,'-* It is pos-sible that failure initiated within the porcelain nearthe side of loading and progressed to the interface.ome distance away. However, previous investi-gators have concluded that it is difficult to deter-mine the origin of fracture from the appearance ofthe fracture surface alone.^•''

The rectangular planar shear test used in thepresent study is essentially the same as thatdescribed by Susz et aP and Oilo et al.^ Metalceramic bond strengths observed in this investi-gation (13.3 throtigh 16.8 MPa, see Table 3), aswell as calculated coefficients of variation (9.0%through 24.2%), are similar to their results. Susz etaP reported bond strengths of 10.9 through 15.9MPa and coefficients of variation of 2 .1% through16.0%. Oilo et al^ reported adherence values of13.1 through 7 5.2 MPa and coefficients of variationof 11 % through 23%. Chong and Beech'' describeda similar shear test, using specimens with a circularcross section and load application directly on por-celain without intervening resin. Bond strengths of1.7 through 27.3 MPa and coefficients of variationof 9% through 57% were reported.

Clinical failures differ from those induced in sim-ple in vitro bond strength tests commonly used tocompare metal ceramic systems. As a result,expected clinical performance may sometimes dif-fer from that predicted by in vitro studies. Resto-rations are exposed intraorally to prolonged cyclicloading, below their failure limits, in a moist envi-ronment that facilitates corrosion-typed reactionswithin porcelain. In addition, geometries of dentalrestorations are usually more complex than are typ-ical in vitro test specimens. These intraoral con-ditions decrease porcelain strength and may alterthe failure mechanism." " Until long-term clinicaldata are available for new materials, in vitro testingis the only means of comparison with materialsknown to function well in the oral environmentand is the only way to detect potential materialshortcomings.

Conclusions

Two types of opaque porcelain were used withone body porcelain on six alloys for metal ceramicbonding. The specimens were subjected to shearstress and the failure loads were recorded. Underthe conditions of this investigation, the followingconclusions may be made:

The International Journal of Proslhodontu 508 • S, Number 6, 1992

Lund/Davis

1- The shear bond strength of the texturedopaque porcelain (Ultra-Pake) was not signif-icantly different from that of the conventionalopaque (Paint-O-Pake] for all alloys tested.

2. More opaque porcelain remained after testingon the specimens with textured opaque thanon those to which the conventional opaquehad been applied.

3. Significant differences in shear bond strengthsexisted between alloys for the texturedopaque porcelain but not for the conventionalopaque.

Acknow iedgments

The authors thank Ceramco Inc, lelenko Denial Health Prod-ucts, and Talladium inc for supplying materials and lane R.Jakobsen for statistical analysis.

References

1. Lund PS, Aquilino SA, Dixon DL Evaluation of the colorand appearance oí 3 new textured opaque porceiam. intJ Prosthodont t991;4;548-554.

2. Anusavice KJ: Screening tests for metal-ceramic systems,in McLean |W (ed): Dental Ceramics—Proceedings oí theFirst Internationai Symposium on Ceramics, Chicago,Quintessensce Publ Co Inc, 1983, pp 371-414.

Shear Bond Strength of Textured Opaque Porceiain

3. Anusavice K], DeHoff PH, Fairhurst CW: Comparativeevaluation of ceramic-metal bond tests using finite ele-ment stress analysis. ; Dent Res t9e0;59:608-6l 3.

4. Chong MP, Beech DR: A simple shear test to evaluate thebond strength of ceramic fused to metal. Austral Dent J1980:25:357-361.

5. Olio G, lohansson B, Syverud M: Bond strength of por-celain to dental alloys—an evaluation of two test methods.Scand J Dent Res 1'581:89:289-296.

6. DeHoff PH, Anusavice K|, Hathcock PVi'; An Evaluationof the four-point flexural test for metal-ceramic bondstrength. ; Dsnt Res 1982,-61:1066-1069.

7. Susz CP, Meyer JM, Payan J, Stoian M, Sanchez |: Influ-ence des traitements précédant la cuisson de la porcelainesur la resistance de la liaison céramo-métallique. RevMens SuÍ5se Odon/o-slomáíoí 1980:90:393-404.

ß, Jones DW: The strength and strengthening mechanismsofdentalceramics, in McLean |W|ed¡: Dental Ceramics-Proceedings of the First Internationai Symposium onCeramics. Chicago, Quintessence Publ Co Inc, t983, pp83-141.

9. Craig RG (ed|: Restorative Dental Materiais, ed B. 5t Louis,CV Mosby Co, 1989, p 79.

10. Nielsen ]P, Tutcillo J]: Calculation of interfacial stress indental porcelain bonded to gold alloy substrate. / DentRes 1972;51:I043-1047.

11. Vl̂ alton TR, O'Brien W|: Thermal stress failure of porcelainbonded to a palladium-silver alloy. / Oen( Res1985:64:476-480

Literature Abstract.

Allergic Reactions to Rubber Gloves in Dental Patients:Report of Three Cases

As a result of the growing awareness of the need for infection control in dentistry, increasing numDersof dentai practitioners are wearing rubber surgical gloves while treating patients. Réactions occurringin patients as a result of the operator wearing gloves are not well recognised. This article describesthree dental patients who presented with perioral symptoms and rashes as a result ot dentalpersonnel wearing rubber gloves and were subsequently shown to be allergic to rubber by consultantdermatologists. Patch tests to a range of rubber accelerators and antioxidants confirmed these to bethe most common cause of the reactions. Two of the patients were aware of possible allergy todomestic rubber products but drd not reveal this as part of their medical history. With the increasingnumber of dentists wearing rubber gloves it is probable that there will be many more patientsexhibiting allergic reactions to the constituents of the gloves. Theretore, it may be advisable to askspecifically about rubber allergies as part of the medical history. It patients have a known allergy torubber, the possible evocation of an anaphyiactic-typed reaction should be remembered and serve asa warning to all practitioners to have an emergency kit available.

Smart Efl, Macleod fit, Lawrence CM. Sr DsnfJ 1992:172:445-447. Rslerences: 6. Reprints: E.H. Smart,Department of Operative Dentistry, Ttie Dental Scinool. University of Newcastie jpon Tyne, Framlington Place,Newcastie jpon Tyne NE2 4BW—Hicfiarö R, Seals, Jr tDDS. MEÓ, MS. Department of ProsttJoOonlics. Ttie Universityot Texas Health Science Center at San Antonio, Texas

Volume 5, Number 6, 1992 509 The internalionai Journal oí Prosthodonlics