Bond Strengths of Dbr to Ni Cr Alloy

354 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 80 NUMBER 3

The most commonly used cast metal alloys forremovable partial denture (RPD) frameworks are nick-el-chromium-beryllium (Ni-Cr-Be) and cobalt-chromi-um (Co-Cr). An acrylic denture base resin joins theartificial teeth and metal framework together to formthe supporting base. Conventionally, denture base

acrylic resin is attached to the metal framework bymechanical retention in many forms, including loops,nail heads, mesh, triangular projections, struts, andundercut finish lines. Livaditis1 described a chemicaletching method to improve retention between acrylicresin and alloy. Zurasky and Duke2 reported that elec-trochemically etched alloy and acrylic resin demon-strated 3.5 times stronger bonding than beads. Theyrecognized that adhesion was entirely mechanical.Krueger et al.3 found that the chemical etching demon-strated the higher bond strength than electrolytic etch-ing. Some articles described chemical etching for themetal alloy.4,5 The major problem with mechanicalbonds is microleakage of the resin-metal interface lead-

Comparison of bond strengths of three denture base resins to treatednickel-chromium-beryllium alloy

Darunee P. NaBadalung, DDS,a John M. Powers, PhD,b and Mark E. Connelly, DDSc

University of Washington, School of Dentistry, Seattle, Wash.; and University of Texas–HoustonDental Branch, Houston, Texas

Purpose. In-vitro bond strengths of 3 denture base resins (Trutone, Lucitone 199, and Triad) to a nickel-chromium-beryllium removable partial denture alloy (Ticonium) were tested with 3 surface pretreatments:sandblast, acid etch, and Rocatec (silica blasting), with or without primers (Dentsply, CR inlay cement, andSuper Bond).Material and methods. Lucitone 199 denture base resin bonded to the nonprimed sandblasted alloyspecimen served as the control group. Alloy specimens were prepared, surface treated, and primed or notprimed with primer. The treated specimens were then packed and processed with the denture base resin.Bonded specimens were stored in the distilled water at 37°C for 24 hours, and then debonded in tension.The force at which the bond failed was noted, and bond strength was calculated in megapascals (MPa). Fivereplications for each condition (180 specimens total) were tested.Results. Significant differences in bond strength were observed with primer, the most important factor,followed by pretreatment and denture base resin. Without primer for all 3 denture base resins, the Met-Etchand Rocatec treated groups showed significantly higher bond strengths than the sandblasted groups. ForTrutone denture base resin, nonprimed treated groups produced significantly higher bond strength thanthose for the other 2 denture base resins. The control group had zero bond strength. For Dentsply primer,the Rocatec treated group bonded to Lucitone 199 resin produced the highest bond strength value (14.8 ±1.8 MPa). For CR inlay cement, the Met-Etch and Rocatec treated groups for Lucitone denture base resindemonstrated the highest bond strength (19.3 ± 4.8 MPa, and 19.3 ± 1.8 MPa, respectively). For SuperBond primer, the Met-Etch treated group for Trutone resin demonstrated the highest bond strength (19.8± 6.2 MPa).Conclusions. Without primer, the control had the lowest bond strength (0 MPa), and the Trutonegroups showed the highest bond strength (11.7 ± 4.1 MPa). Met-Etch and Rocatec treated groups pro-duced higher bond strengths than the sand blasted groups. The primed specimens demonstrated significant-ly higher bond strengths than nonprimed specimens, except for Trutone resin, for which primed specimensproduced lower bond strengths than the nonprimed specimens. (J Prosthet Dent 1998;80:354-61.)

This research was supported in part by Dentsply International, Inc.,and Gresco Products, Inc.

aAssistant Professor, Department of Prosthodontics, School of Den-tistry, University of Washington.

bProfessor, Department of Basic Sciences, University of Texas-Houston Dental Branch.

cAssociate Professor, Department of General Dentistry, Universityof Texas-Houston Dental Branch.

CLINICAL IMPLICATIONS

Bond strengths between denture base resins and nickel-chromium-beryllium alloy canbe enhanced by using a combination of primer (Dentsply primer, Super Bond cement,or CR inlay cement) and treating metal surface with sandblast, chemical etch (Met-Etch), or the Rocatec system. Future studies are needed to evaluate the long-term clin-ical performance of the denture base resin-treated alloy interface.

ing to ingress of oral fluids, retention of food particlesand microorganisms, and subsequent discoloration,foul odor, and deterioration of acrylic resin portion ofthe prostheses.6 In addition, when the interarch dis-tance is limited, mechanical retention compromisesesthetics and placement of artificial teeth.

Because of the disadvantages of the mechanicalresin-metal bonding, numerous methods and tech-niques to improve the quality of the metal-resin inter-face have been explored. Because Rochette7 used asilane coupling agent to improve bonding betweenresin and metal alloy, researchers8,9 have reported that4-META (4-methacryloxyethyl trimellitate anhydride)adhesive resin adhered strongly to oxidized Ni-Cr alloyand to acrylic resin. Tanaka et al.9,10 obtained a favor-able 4-META bond strength when Ni-Cr alloys weretreated in an oxidizing solution with 1% potassium per-manganate (K2MnO4), and etched with 36% HCl, andfinally oxidized with 61% HNO3. Other reports11-17

observed that alloy treated with adhesive resins con-taining 4-META bonded strongly to the acrylic resin.At the same time, another organic phosphonate adhe-sive resin was reported as a successful material forbonding acrylic resin to sandblasted metal alloys.13,15

Moreover, Guggenberger18 used the Rocatec system toimprove resin-alloy bond strength. The Rocatec systemconsists of cleaning the metal surface with sandblasting(110 µm Al2O3 under 0.25 MPa pressure), coating theblasted surface with high energy silicon dioxide gran-ules under pressure, and coating with a silane couplingsolution to induce a chemical bond. Several reports19,20

showed that the Rocatec system enhanced the bondstrength of the acrylic resin to the alloy. There are noreports on the comparison of the bond strengthsamong Trutone, Lucitone, and Triad denture baseresins to the treated RPD alloy with or withoutprimers.

The purpose of this in vitro study was to comparetensile bond strength of 3 traditional denture baseresins to Ni-Cr-Be alloy prepared with 3 surface pre-treatments and 3 adhesive primers to a control group.Increased bonding between the denture base resin andthe RPD alloy should allow advantageous prostheticdesigns, and eliminate and reduce leakage at the finishline.

MATERIAL AND METHODS

The codes, products, batch numbers, and manufac-turers of denture base resins, adhesive primers, and pre-treatments are listed in Table I.

Truncated cones (8 mm diameter at the bond inter-face × 10 mm in diameter × 10 mm height) of hardinlay wax (Lincoln Dent. Inc., Cherry Hill, N.J.) wereprepared, invested, and cast in Ni-Cr-Be alloy (Ticoni-um Premium 100, Ticonium Co., CMP Industries Inc.Albany, N.Y.) with an induction casting machine (Tico-matic, CMP Industries Inc.). Alloy specimens weredevested and finished with sandblasting at 0.25 MPawith 50 µm Al2O3 (aluminum oxide, Sinclair Abrasiveand Equipment Co., Chicago, Ill.) for 10 seconds,cleaned ultrasonically for 1 minute in distilled water, airdried, and then examined thoroughly for any bonding

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SEPTEMBER 1998 355

Table I. Code, products, batch numbers, manufacturers, denture resins, adhesive primers, and pretreatment agents

Code Product Batch number Manufacturer

Denture base resinsC20 *Trutone Powder 49631002 Dentsply Int. Inc., York, Pa.

(Compak 20) Liquid 94963L †Lucitone 199 Powder 688106 Dentsply Int. Inc.

Liquid 684309T #Triad 95791 Dentsply Int. Inc.Adhesive primersD Dentsply Liquid LF 1-73A Dentsply Int. Inc.SB Super Bond primer Powder 91201; Liquid 007; Catalyst 005012 Sun Medical Co., Kyoto, JapanCR CR Inlay cement Powder ID-1082 Liquid 007 J. Morita Inc., Tustin, Calif.Surface pretreatmentS Sandblast (50 µm Al2O3) None Sinclair Abrasive and Equipment Co.,

Chicago, Ill.ME Met-Etch 01132 Gresco Product, Inc., Stafford, TexasR Rocatec system Rocatec-pre 0004 ESPE Seefeld, Germany

Rocatec-plus 0036 Norristown, Pa.Rocatec-sil 002

Ni-Cr-Be alloy Ticonium Premium 100 None Ticonium Co., Albany, N.Y.

*Powder-liquid ratio was 100 g/42.8 g. Polymerization conditions were 100°C for 20 minutes in water bath.†Powder-liquid ratio was 100 g/47.6 g. Polymerization conditions were 74°C for 9 hours in water bath.#Polymerization conditions were 10 minutes in Triad II (Dentsply Int. Inc.).

surface defects. Alloy specimens without defects wereselected for this study.

Alloy specimens, with matching truncated cones ofinlay wax (Fig. 1) attached on the bonding surface,were invested in dental stone (5 specimens at a time)within a traditional denture flask (Hanau EngineeringCo. Inc., Buffalo, N.Y.). After the stone was set and thewax was boiled out, specimens and stone molds wererinsed of the wax residue, cleaned thoroughly withdetergent, and washed with boiling water. The bondingsites (50.8 mm2 in area) of alloy specimens were pre-pared with surface pretreatments (sandblast, S; acidetch, ME; Rocatec, R). Sandblasting was performedwith 50 µm Al2O3 particles at 0.25 MPa for 1 minuteand washed thoroughly with distilled water and then airdried. Chemical etching was performed with an acid gelmixture of HNO3, HCl, and HF acids (Met-Etch,

Gresco Products Inc. Stafford, Texas) for 20 minutes,then rinsed with distilled water, and air dried for30 minutes, according to the manufacturer’s instruc-tions. The Rocatec treatment (Rocatec system, ESPE,Seefeld, Germany) was conducted according to themanufacturer’s instructions, which involved sandblast-ing with 110 µm Al2O3 under pressure 0.25 MPa(Rocatec-Pre) for 26 seconds and silica coating(Rocatec Post) for 26 seconds. Immediately after thecoating, a silanating agent (Rocatec-Sil) was appliedwith a brush-on technique and allowed to dry for5 minutes. Primer was applied and denture base resinwas packed within 15 minutes according to the manu-facturer’s instructions.

Treated specimens were primed with an adhesiveprimer (Dentsply, D; CR inlay cement, CR; and SuperBond C&B, SB) or not primed. D primer contains anacrylic copolymer, thixotropic agent, pigments, silane,and solvents (methyl ethyl ketone and 1,1,1,trichloroethane). It was applied with brush-on tech-nique in 2 separate layers with each layer allowed todry. CR primer is a filled, dual-cured, organic phos-phorylated BIS-GMA that was mixed and applied withbrush-on technique in 1 layer and allowed to dryaccording to the manufacturer’s instructions. SBprimer is a 4-META acrylic resin cement that wasmixed, applied with brush-on technique in 1 layer andallowed to polymerize for 10 minutes. Before applica-tion of the SB primer, the alloy surfaces, which hadbeen pretreated with sandblast and Met-etch, were

THE JOURNAL OF PROSTHETIC DENTISTRY NABADALUNG, POWERS, AND CONNELLY

356 VOLUME 80 NUMBER 3

Fig 1. Alloy specimens with truncated cones of wax.

Fig. 2. Chart of specimens per preparation.

Fig. 3. Bonded specimens (denture base resin-treated alloy).

cleaned and oxidized with freshly prepared1% K2MnO4 and 3% H2SO4 solutions for 10 seconds.

Pretreated and primed or nonprimed specimens andstone molds in the flask were packed with denture baseresins (Trutone, C20; Lucitone 199, L; Triad, T) andprocessed according to the manufacturers’ instructions.One resin was packed and processed with each condi-tion of specimens at a time. The number of specimensper preparation is illustrated in Figure 2. Lucitone199 (L) resin with nonprimed sandblasted specimensserved as the control group. C20 resin, a rapid heat-polymerized resin, was polymerized at 100°C for 20minutes in water. L resin, a traditional heat-polymer-ized acrylic resin, was polymerized at 74°C for 9 hoursin water. C20 and L resins were processed by using theconventional flasking technique. Triad resin, a filledurethane dimethacrylate resin, was polymerized in avisible light-curing unit (Triad II, Dentsply Interna-tional, York, Pa.). Mixed Triad resin was packed to pre-treated alloy specimens in a polytetrafluoroethylenemold without gypsum to allow visible light (Triad II)activation for 10 minutes. Bonded specimens wererecovered after polymerization and then examinedthoroughly. Any flash or excess resin material wasremoved with an inverted cone bur (Brasseler Inc.,Savanna, Ga.).

Bonded specimens (Fig. 3) were stored in distilledwater at 37°C for 24 hours. Afterward, they weremounted in a loading jig and debonded in tension with

a testing machine (Model 8501, Instron Corp., Can-ton, Mass.) at a crosshead speed of 0.05 cm/min. Theforce at which the bond failed was recorded, and thebond strength was calculated in megapascals (MPa).

Treated alloy specimens were examined at 500×magnification with a scanning electron microscope(JSM-820, JEOL, Peabody, Mass.) operating at 30 KVby a coinvestigator. In addition, the sites of the bondfailure were examined under low-power magnification(20×) and with a measuring grid, the area (in %) wascalculated.

Five specimens were evaluated for each experimentalcondition for a total of 180 specimens. Means and stan-dard deviations of bond strength were calculated andrecorded. Data were analyzed with a 3-way analysis ofvariance (ANOVA) with a factorial design,21 and meanswere compared with Tukey intervals22 calculated at the0.05 significance level. Differences between means thatwere larger than the calculated Tukey intervals wereconsidered statistically significant.

RESULTS

Means and standard deviation (n = 5) of the bondstrength data are presented in Table II, and ANOVAresults are listed in Table III. Tukey intervals for com-parisons among means at 0.05 significance levelwere 1.6 MPa among 3 adhesive primers and control,1.2 MPa among 3 pretreatments, and 1.2 MPa among3 denture base resins. Differences between 2 meansgreater than the appropriate Tukey intervals were con-sidered statistically significant. Significant differences inbond strengths were observed among primers, pre-treatments, and denture base resins with significantinteractions. Two-way interactions were all significant(P=.0001); however, the 3-way interaction was not sig-nificant.

Nonprimed specimens

The control group exhibited zero bond strength.The Met-Etch (ME) and Rocatec (R) treated groupsshowed the significantly higher bond strengths for each


SEPTEMBER 1998 357

Table II. Tensile bond strength (MPa) of denture base resinsto pretreated Ni-Cr-Be partial denture alloy

Pretreatment

Denture resin Sandblast, S Met-Etch, ME Rocatec, R

No-primerTrutone, C20 8.0 (1.8)* 11.7 (4.1)a 11.4 (2.7)a,q

Lucitone 199, L 00φ 6.0 (2.6)b,i 7.1 (1.6)b,j

Triad, T 1.9 (0.9) 7.0 (1.4)c,i 7.0 (2.1)c,j

Dentsply, DTrutone 1.0 (0.1)k 7.7 (2.2)d,l 7.7 (1.2)d

Lucitone 1.9 (0.7)k 7.7 (2.4)l,o 14.8 (1.8)r

Triad 8.9 (1.8)c 9.2 (1.8)e 10.8 (1.4)Super Bond, SBTrutone 4.7 (1.6) 19.8 (6.2) 6.2 (0.8)Lucitone 199 8.8 (1.6)f 8.6 (2.1)f,o 14.8 (1.3)m,r

Triad 11.8 (2.8) 18.2 (3.6)p 14.7 (1.3)m,s

CR Inlay cementTrutone 6.8 (0.4) 13.4 (4.1) 10.9 (3.9)q

Lucitone 199 16.8 (4.4) 19.3 (4.8)g,n 19.3 (1.8)g

Triad 18.2 (4.1)h 18.9 (5.2)h,n,p 14.8 (4.9)s

*Mean of 5 replications (MPa) with standard deviation in parentheses. φCon-trol. Tukey intervals (MPa) for comparisons among means at the 0.05 signifi-cance level (P<.05) were 1.6 MPa among 3 adhesives and nonprimed con-trol, 1.2 MPa among 3 pretreatments, and 1.2 MPa among 3 denture baseresins. Means with same superscripts are statistically equal at 0.05 signifi-cance level.

Table III. Analysis of variance table for bond strengthsaffected by primer, resin, and pretreatment

Sum of MeanSource df square square F value P values

Primer (P) 3 2161 720 87.6 .0001Resin (R) 2 219 110 13.4 .0001Pretreatment (T) 2 845 423 51.4 .0001P*R 6 1002 167 20.3 .0001P*T 6 260 43.4 5.27 .0001R*T 4 401 100 12.2 .0001P*R*T 12 435 36.3 4.42 >.05Residual 144 1184 8.22

resin than the sandblasted groups (P<.05). The valuesof the R and the ME groups were not significantly dif-ferent. The Trutone groups showed the significantlyhigher bond strengths than the other 2 resin groups.

Primed specimens

For Dentsply (D) primer, for 3 resins, the ME and Rtreated groups demonstrated significantly higher bondstrengths than the sandblasted (S) group, except forTriad resin for which the bond strengths of the S andME treated groups were not significantly different. Forthe Lucitone and Triad resins, the R group producedsignificantly higher bond strengths (14.8 ± 1.8 and10.8 ± 1.8 MPa) than the ME groups (7.7 ± 2.4 and9.2 ± 1.8 MPa), but for the Trutone resin, both MEand R treated groups were not statistically different(7.7 ± 2.2 and 7.7 ± 1.2 MPa). However, for 3 resins,the D primer groups produced higher bond strengths

than the nonprimed groups, except for Trutone resinfor which the primed groups demonstrated the signifi-cantly lower bond strengths than the nonprimedgroups.

The highest bond strength of the D primer groups(14.8 ± 1.8 MPa) was the bond strength of the Luci-tone 199 to the R treated group. This value was signif-icantly higher than the bond strengths of the othergroups with D primer.

With the SB primer for these 3 resins, the ME andthe R treated groups produced the significantly high-er bond strength than the S groups, except for Luci-tone resin with ME and S groups, for which the valueswere not significantly different (8.6 ± 2.1 and 8.8 ±1.6 MPa). Super Bond primer groups demonstratedsignificantly higher bond strengths than the non-primed groups, except for Trutone resin with the Sand R treatments. In these situations, the SB groups



Fig. 4. A, SEM photograph of sandblasted Ni-Cr-Be alloy showed microretention area. (Orig-inal magnification ×500.) B, SEM photograph of Met-Etched Ni-Cr-Be alloy showed microre-tention areas. (Original magnification ×500.) C, SEM photograph of Rocatec treated Ni-Cr-Bealloy showed silica with silane on alloy surface. (Original magnification ×500.)

demonstrated significantly lower bond strengths thannonprimed groups. In addition, the SB groups pro-duced significantly higher bond strengths than Dprimer groups, except for Trutone resin to R with theSB or D groups (6.2 ± 0.8 and 7.7 ± 1.2 MPa) and forLucitone resin to ME with the SB or D groups (8.6 ± 2.1and 7.7 ± 2.4 MPa) for which the bond strengths werenot significantly different. The highest bond strengthof the SB primer groups (19.8 ± 6.2 MPa) was thebond strength of the ME group with SB primer toTrutone resin, and this value was significantly higherthan the bond strengths of the other groups with theSB primer.

With the CR inlay primer (CR), for 3 resins, the MEand R groups revealed significantly higher bondstrength than the S groups, except for Triad resin forwhich the S group produced significantly higher bondstrength (18.2 ± 4.1 MPa) than the R treated group(14.8 ± 4.9 MPa). The CR primer groups producedsignificantly higher bond strengths than nonprimedgroups, except for the Trutone groups for which thebond strengths of the CR primer and nonprimedgroups were not significantly different. CR primergroups produced significantly higher bond strengthsthan the SB primer groups, except for Trutone resinwith the ME groups for which the CR group producedsignificantly lower bond strength (13.4 ± 4.1 MPa)than the SB group (19.8 ± 6.2 MPa), and for the Triadresin with the ME and the R groups, for which CRand SB groups were not significantly different (18.9 ± 5.2and 18.2 ± 3.6 MPa). In addition, the CR primergroups produced significantly higher bond strengthsthan the D primer groups, especially for the Lucitoneand Triad resins.

The highest bond strengths of the CR primergroups (19.3 ± 4.8 and 19.3 ± 1.8 MPa) were the bondstrengths of the ME and the R treated specimens toLucitone resin. These values were significantly higherthan bond strengths of the other groups with the CRcement, except these values and the bond strength ofthe Triad resin to the ME with CR group were not sig-nificantly different (18.9 ± 5.2 MPa).

SEM studies of the alloy pretreatments demonstrat-ed the S specimen (Fig. 4,A), ME specimen (Fig. 4,B),and R specimen (Fig. 4,C). The ME surface showedmore irregularly shaped microretention areas than theS surface. The R treated surface showed a silica-silanecoated surface.

Failure sites

Data for bond failures are summarized in Table IV.Without primer, for Lucitone resin, 100% of the bondfailures occurred adhesively between the denture baseresin and treated alloy. For Trutone and Triad resins,80% to 100% of the bond failures occurred adhesivelybetween denture base resins and treated alloy and 0% to

20% of bond failures occurred cohesively within theresins.

With Dentsply primer (D), for Lucitone resin, 0% to100% of the bond failures occurred cohesively withinthe primer and 0% to 100% of the bond failuresoccurred adhesively between the primer and alloy. ForTrutone and Triad resins, 0% to 100% of the bond fail-ures occurred cohesively within the primer, 0% to 90%of the bond failures occurred adhesively between resinsand alloy, and 0% to 30% of the bond failures occurredcohesively within the resins.

With SB primer, for Lucitone resin, bonds failedadhesively (10% to 40%) between the primer and resin,and cohesively (60% to 90%) within the resin. For Tru-tone and Triad resins, bonds failed adhesively (0% to60%) between the primer and resins, and cohesively(40% to 100%) within the resins.

With CR cement, for Lucitone resin, bond failuresoccurred adhesively (20% to 100%) between the primerand resin, and cohesively (0% to 80%) within the resin.For Trutone resin, bond failures occurred adhesively(50% to 80%) between the primer and resins, and cohe-sively (20% to 50%) within the resin. For Triad resin,bond failures occurred cohesively (100%) within theresin.

DISCUSSIONWithout primer

This study indicated that for the 3 denture baseresins tested, the ME and R groups produced bond


SEPTEMBER 1998 359

Table IV. Location of bond failures (%) of denture base resinto pretreated Ni-Cr-Be partial denture alloy

Pretreatment

Denture resin Sandblast, S Met-Etch, ME Rocatec, R

No primerTrutone, C20 85AR/15R* 85AR/15R 85AR/15RLucitone 199, L ARφ AR ARTriad, T AR 80AR/20R 80AR/20RDentsply, DTrutone, C20 P 70AR/30R PLucitone 199, L AP P PTriad, T P P 90AR/10RSuper Bond, C&BTrutone, C20 30PR/70R R 60PR/40RLucitone 199, L 40PR/60R 40PR/60R 10PR/90RTriad, T 20PR/80R 20PR/80R 10PR/90RCR Inlay cementTrutone, C20 80PR/20R 50PR/50R 75PR/25RLucitone 199, L PR 20PR/80R 60PR/40RTriad, T R R R

R is cohesive failure within the denture base resin. AP is adhesive failurebetween alloy and primer. P is cohesive failure within the primer. PR isadhesive failure between the primer and denture resin. φ is the controlgroup.

strengths higher than the S groups. This may bebecause the ME treated groups produced more irregu-lar surface areas, and a more uniform oxide layer on thetreated alloy, thereby enhancing the bond strengths ofthe denture base resins to the treated alloys more thanthe S group. For the Rocatec system, both the chemi-cal agent from the silane agent and increased microme-chanical retention areas from silica blasting were usedto enhance the bond strength of the denture base resinsto the treated alloy. ME and R treated groups did notproduce significantly different bond strengths. Thecost may be a factor in system selection because theRocatec system is much more expensive. For Lucitoneresin, ME and R groups demonstrated bond strengthsof 6.0 to 7.1 MPa, which were substantially higher than4.77 MPa for bead retention.2 This suggests that Met-Etch and Rocatec treatments are better than the beadretention to enhance the bond strength between thetreated alloy and Lucitone denture base resin. Howev-er, without primer, the Trutone and Triad resinsadhered to the treated alloy better than the Lucitoneresin.

With primers

Dentsply primer, a resin base with silane agent,worked well with the Lucitone and Triad resins to thetreated groups, especially with Lucitone resin to theRocatec treated alloy, where it produced a high bondstrength (14.8 ± 1.8 MPa). In contrast, it did notenhance the bond strengths of the Trutone resin to thetreated groups when compared with the nonprimedgroups. Interestingly, bond failure occurred cohesivelywithin the primer. Perhaps the tensile strength of theprimer was low to start with or the temperature (100°Cfor 20 minutes) for polymerization of the Trutone resindegraded the primer.

Super Bond primer, an acrylic 4-META base primer,worked well with the Met-Etch treated alloy to Triadand Trutone resins, and produced the higher bondstrengths (18.2 to 19.8 MPa) and the bond failuresoccurred cohesively within the resins (80% for the Triadand 100% for the Trutone). For Trutone resin group,most bond strengths of the primed groups were signif-icantly lower than the bond strengths of the nonprimedgroups, except the ME treated groups with the SuperBond, which had significantly higher bond strengthsthan the nonprimed groups. The high temperature(100°C, 20 minutes) for polymerization of Trutoneresin may have enhanced the properties of Met-Etchwith the Super Bond, or the high temperature degrad-ed the properties of the primers. However, furtherresearch is necessary in these areas. In addition, theSuper Bond procedure was complicated due to thenecessity of using K2MnO4 and H2SO4 solutions toinduce the oxide on the metal surface as suggested byTanaka et al.10

Super Bond primer worked well with the Rocatectreated alloy to Lucitone and Triad resins and producedthe high bond strengths (14.7 to 14.8 MPa) and thebond failures mostly occurred cohesively (90%) withinthe resins. However, the Rocatec system is more expen-sive and complicated than the Met-Etch.

The CR inlay cement, a composite phosphonateBIS-GMA base primer with an activated ester toenhance chemical adhesion to the treated alloy and tothe denture base resin, seemed to bond effectively innearly all conditions and to yield significantly higherbond strengths. In addition, the manufacturer statesthat cement bonds strongly to resin. Another factormay be the property of the CR inlay cement to com-pletely wet the treated alloy surface. For the Lucitoneand Triad resins, the CR inlay cement yielded highbond strengths from 14.8 ± 4.9 to 19.3 ± 4.8 MPa, andthe bond failures occurred mostly cohesively within theresins (100% for Triad and 0% to 80% for Lucitone) andadhesively between the resins and the CR inlay primer(0% for Triad and 20% to 100% for Lucitone).

For Trutone groups, the CR inlay cement yieldedthe bond strengths lower than the nonprimed groups,perhaps the high temperature (100°C for 20 minutes)for polymerization of the resin degraded the adhesionproperties of the CR inlay cement. Further research isnecessary in this area.

When compared with the results of the report byZurasky and Duke,2 the results from this study showedthat 31 conditions of the specimens had bond strengthsthat were higher than 4.77 MPa, which was the bondstrength of Lucitone resin to Ni-Cr-Be alloy when beadretention was used, and there were 7 conditions thathad the bond strength higher than 16.7 MPa, whichwas the bond strength of the Lucitone resin to the elec-trochemically treated alloy. In addition, a previousreport stated that a strong adhesion mediated by abonding agent may be gap free.23 The results of thisstudy indicated the selected combinations to enhancethe bond strength between the alloy surface and den-ture base resin and could be worthy for clinical evalua-tion. Furthermore, the required thickness of the primeris much less than the size of the bead or stud retention.Therefore the bonding agents would preserve the nec-essary space for the artificial teeth or denture base resinand enhance the quality of the prosthesis. However,further research of microleakage between the bondinginterface of the specimens is necessary.

SEM microphotographs of the alloy surfaces pre-treatment demonstrated the differences of microreten-tion areas of the treated specimens. The Met-Etchtreated alloy had more microretention areas than sand-blasted alloy. The Rocatec treated alloy showed a silica-silane coated surface. Both Met-Etch and Rocatectreated specimens demonstrated more microretentionareas than the sandblasted alloy.




SEPTEMBER 1998 361

CONCLUSIONSWithin the limitations of this study, the following

conclusions were drawn.1. Without primer, Lucitone 199 resin showed zero

bond strength with the sandblasted surface pretreat-ment. Trutone resin showed significantly higher bondstrength than Lucitone or Triad resin. Met-Etch andthe Rocatec treated groups showed the significantlyhigher bond strength than the sandblasted groups.

2. With primer, the primed groups showed signifi-cantly higher bond strengths than nonprimed values,except for the Trutone groups in which the primedgroups produced lower bond strengths than the non-primed groups.

3. For Lucitone resin, the Met-Etch and Rocatectreated groups with CR inlay cement produced the high-est bond strengths (19.3 ± 4.8 and 19.3 ± 1.8 MPa).

4. For Triad resin, the Met-Etch treated groups withCR inlay cement and Super Bond primer, and the sand-blasted group with CR inlay cement, demonstratedhigher bond strengths that were not significantlydifferent from each other (18.9 ± 5.2 and 18.2 ±4.1 MPa). For Trutone resin, the Met-Etch treatedgroup with Super Bond primer demonstrated the high-est bond strength (19.8 ± 6.2 MPa).

5. Nearly all bond failures of the primed groupsoccurred cohesively within the primers or denture baseresins and adhesively between the primers and thereins; whereas, most of the nonprimed groups occurredadhesively between the metal surface and the denturebase resins.

The commercial products were provided by Dentsply Int., Inc., ESPECo., Gresco Products, Inc., Sun Medical Co., Ltd., and TiconiumCo./CMP Industries, Inc. We thank David Ladd and U. Parikh fortechnical assistance.

REFERENCES

1. Livaditis GJ. A chemical etching system for creating micromechanicalretention in resin-bonded retainers. J Prosthet Dent 1986;56:181-8.

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Documents

Bond Strengths of Dbr to Ni Cr Alloy