Bonding fixed prosthodontic composite resin and precious metal alloys with the use of a vinyl-thiol primer and an adhesive opaque resin Mitsuru Atsuta, Takuo Tanaka,

DDS, DDSC,~ Hideo DDS, DDScC

Nagasaki

School

University,

of Dentistry,

Matsumura,

Nagasaki,

DDS, DDSC,~ and

Japan

Adhesive bonding of a light-cured fixed prosthodontic composite resin joined to silverand gold-based alloys was investigated with the use of a metal primer and an adhesive opaque resin. The primer contained an adhesive bonding promoter for precious alloys, 6- (4-vinylbenzyl-n-propyl) amino-l, 3, 5-triazine-2,4-dithiol (VBATDT). The cast metal specimens were alumina-blasted and primed with VBATDT acetone solution. A self-curable 4-META/MMA-TBB opaque resin was used to bond the primed metals and a light-cured composite resin. Prepared specimens were thermocycled in water and bond strengths were determined. The shear bond strengths after 100,000 thermocycles (4’ C to 60’ C for 1 minute) were 28.4 MPa for Ag-Pd-&-Au alloy and 20.8 MPa for type III gold alloy. This simple method may be used to bond silver or gold alloy and light-activated fixed prosthodontic composite resin. (J PROSTHET DENT 1992;67:296-300.)

c

omposite resin veneered prostheses made with a high-strength composite resin and gold- or silver-based alloy have recently shown fairly acceptable prognoses compared with conventional thermoplastic resin-veneered prostheses. This progress is mainly due to the improvement of strength, abrasion resistance, and color stability of veneer materials. One of the requirements of composite resin-veneered prostheses is a strong bond between the metal framework and composite resin. Various adhesive bonding promoters have been used in the laboratory procedure.le3 Bonding to the base metal alloys has considerably improved with the use of water-resistant carboxylic or phosphoric acid derivatives.2, 4-7These monomers, however, have never strongly bonded to precious alloys, hence surface preparations of the metal frameworks have been indispensable to produce metal oxides at the surfaces to be bonded. However, these methods required an expensive apparatus and troublesome procedures. Some organic compounds with mercapto groups showed bonding ability to the precious metals. A polysulfide rubber impression material bonded to copper bands, copperplated acrylic resin tray material,s and precious metal prostheses in the mouth. Kojimag reported that a metal primer that contained N-(4-mercaptophenyl)methacrylamide (MPMA) strongly bonded to gold, palladium, and copper. However, the application of thiols to the dental adhesive, especially to acrylic resin-based adhesives, has aProfessor, bLecturer, CAssociate 10/l/29660

296

Department Department Professor,

of Fixed of Fixed Department

Prosthodontics. Prosthodontics. of Fixed Prosthodontics.

CH2=CH-@CH2-+3H I W&H&H,

S

i

‘SH

CH,CH,CH, Fig. 1. Structural formula of VBATDT type (=S) and thiol type (-SH).

tautomer. Thione

been difficult because of the so-called chain transfer reaction. This article describes a simple bonding method of a light-activated fixed prosthodontic composite resin and precious alloys with the use of a triazine dithiol derivative and an adhesive opaque resin. MATERIAL

AND

METHODS

The alloys used were type III gold alloy (Midas, J. F. Jelenco & Co., New Rochelle, N.Y.) and Ag-Pd-Cu-Au alloy (New Au-Pd, J. Morita Corp., Suita, Japan). The metal primer was 0.5% 6- (4-vinylbenzyl-n-propyl) amino-l, 3,

MARCH1992

VOLUME67

NUMBER3

BONDING

Table

COMPOSITE

RESIN

AND

PRECIOUS

ALLOY

Alloys, primer, opaque resin, and composite resin used

I. Material

Composition

Nilme

Manufacturer J. F. Jelenko & Co. New Rochelle, N.Y. J. Morita Corp. Suita, Osaka, Japan

Primer

Type III, Midas (2197 010683) Ag-Pd-Cu-Au, New Au-Pd (111386) VBATDT primer

Opaque resin

4-METAMMA-TBB opaque resin*

Trial

Composite resin

Dentacolor,

Kulzer

Alloy

*A similar

D-120

(7 1 227)

product

is on the market

opaque

ivory

Ag 51, Pd 20, Cu 14.5, Au 12 VBATDT, 0.5 Acetone, 99.5 InitiatorTri-n-butylborane derivative Monomer-MMA, 95 4-META, 5 PowerPulverized PMMA, 80 PMMA-coated titanium dioxide,

Germany

(Sun-Medical

Co. Ltd.,

Kyoto,

alloy and light-cured

Japan).

composite resin Shear

bond

strength

Thermocycles Group

Metal

11 12 13 14

‘Derived

surface

Alumina-blasted Alumina-blasted Alumina-blasted Alumina-blasted tion-coated from

Matsumura

Primer

VBATDT VBATDT -

H, et al. J Jpn

Prosthodont

Opaque

resin

4-METAMMA-TBB MMA-TBB (without 4-METAMMA-TBB 4-METAMMA-TBB

Sot

JOURNAL

OF PROSTHETIC

DENTISTRY

0

4-META)

29.1 35.2 35.9 42.3

+ + + t

20,000 3.71 2.5 1.7 2.11

4.0 22.3 33.3 30.4

t + zk t

+ SD (MPa) (cycles) 50,000

1.11 7.4 1.6 4.11

0 20.2 + 8.9 33.1 k 0.4 25.6 + 4.5l

100,000

14.0 t 5.7 28.4 + 2.6 27.4 t 2.4

1988;32:1306-10.

5-triazine-2,4-dithiol (VBATDT) in acetone (Fig. 1). The VBATDT monomer was reported by Mori et al.‘Ovl1 and Kojima et al. I2 to be an adhesive bonding promoter for copper or precious dental alloys. A self-curing opaque resin, 4-META/MMA-TBB opaque resin, was used to bond metal specimens and light-cured veneering composite resin. The opaque resin was initiated by tri-n-butylborane derivative (TBB).i3 The monomer liquid of the opaque resin was 5 % 4-methacryloxyethyl trimellitate anhydride (4-META)14 in methyl methacrylate (MMA). The opaque resin powder consisted of 20% poly(methy1 methacrylate)coated titanium dioxide6 and 80% pulverized poly(methy1 methacrylate) (PMMA). The opaque resin was applied by brush. The composite resin was a visible-light-activated fixed prosthodontic composite resin (Dentacolor, D-120, Kulzer & Co., GmbH., Friedrichsdorf, Germany). The materials used in this study are listed in Table I. Metal specimens (10 mm in diameter by 2 mm) were cast in type III gold and Ag-Pd-Cu-Au alloys according to the manufacturers’ instructions. The surfaces to be bonded were sanded with no. 600 silicon-carbide paper and were blasted with alumina of grain size 50 pm for 10 seconds by a sandblaster (Pen-Blaster, Shofu Inc., Kyoto, Japan). The

THE

20

& Co., GmbH.

II. Shear bond strength between Ag-Pd-&-Au

Table

Au 46, Ag 40, Cu 8, Pd 6

production

Friedrichsdorf, as Superbond

(%)

emission pressure was 5 kgf/cm2, and the distance of the nozzle from the alloy surface was 5 mm. The specimens were air-blasted and primed with VBATDT primer. The primed surface dried quickly because the acetone solvent was volatile. A piece of bisided tape with a circular hole 5 mm in diameter was put on the primed surface of each specimen. The opaque resin was brushed on the 5 mm diameter surface to a thickness of about 200 pm. Before complete hardening of the opaque resin, a brass ring (6 mm inside diameter by 2 mm long and with a 1 mm thick wall) was placed surrounding the opaque resin. The ring was filled with composite resin. Specimens were irradiated for 270 seconds by means of a visible-light source (Dentacolor XS, Kulzer & Co.). After 30 minutes, the specimens were immersed in 37O C water for 24 hours. This state was defined as thermocycle 0. The specimens were continuously placed in the thermocycling machine (Rika-Kogyo, Hachioji, Japan) and dipped for 1 minute in 4“ C and 60’ C water alternately for up to 100,000 cycles to evaluate the durability of the bond. The 100,000 thermocycles required 200,000 minutes (about 139 days). Shear bond strengths were next measured with a univer-

297

ATSUTA.

Table

III.

MATSUMURA,

bond

strength

Tbermocycles Metal

surface

21

Alumina-blasted

22 23

Alumina-blasted Alumina-blasted

Primer

Opaque

0

resin

4-META/MMA-TBB VBATDT VBATDT

MMA-TBB (without 4-META/MMA-TBB

sal testing machine (DCS-500, Shimadzu Corp., Kyoto, Japan) at a cross-headspeedof 0.5 mm/min. The assembly usedto determine shear strength wasthe sameasthat previously described.15 Three types of specimenswere alsoprepared ascontrols for the sheartest. Groups 11and 21 (Tables II and III) were unprimed specimens. The 4-META opaque resin was directly applied to the alumina-blasted metal surface. Groups 12and 22 were primed with VBATDT primer. The opaqueresin, however, did not contain 4-META monomer. The monomerliquid of the opaqueresin was 100% MMA. Group 14wasanother type of control. The alumina-blasted metal specimenswere ion-coated with copper oxide by a sputter-coater. The experimental procedureof ion-coating was the sameas that previously reported by us.15-17 For eachcondition, the mean and standard deviation of five replications were calculated. The values of eachgroup were comparedby analysisof variance and by Tukey multiple comparisonintervals, with the value of statistical significance set at the p < 0.05 level. Debonded surfaces were observed through an optical microscope(SMZ-10, Nikon Corp., Tokyo, Japan) and locations of failure were recorded aswithin the opaqueresin (cohesive),at the opaqueresin-metal interface (adhesive), and a mixture of both (cohesive-adhesive).

RESULTS Tables II and III showthe shearbond strengths between alloys and prosthodontic composite resin cemented with VBATDT primer and 4-META/MMA-TBB opaqueresin. Types of bond failures of each specimenare classifiedinto three categories,and the results are summarizedin Table IV. Groups 11 and 21 were alumina-blasted and 4-METAresin-bonded groups without primer. The bond strengths before thermocycling were 29.1 MPa for both Ag-PdCu-Au alloy and type III alloy. The shearstrengthsof these groupsquickly deteriorated by repeatedthermocycling. All the specimensof groups11 and 21 failed at the opaqueresin-metal interface. Specimensof groups 12 and 22 were VBATDT-primed and bonded with MMA-TBB opaque resin that did not contain 4-META. These groups demonstrated longer adhesivebonding durability comparedwith groups11and 21.

298

TANAKA

Shear bond strength between type III gold alloy and light-cured compositeresin Shear

Group

AND

4-META)

(cycles)

20,000

29.1 t 1.1

4.8 It 1.4

31.7 + 3.8 33.5 f 2.1

20.6 k 1.0 36.9 + 0.5

+ SD (MPa)

50,000

100,000

0

-

8.8 I 4.6 31.9 k 1.8

9.1 + 3.7 20.8 k 7.0

Someof the specimensin these groupsshowedcohesiveor partial cohesivefailure. Bond strengthsafter 100,000cycles were 14.0 and 9.1 MPa, respectively. Groups 13 and 23 were VBATDT-primed and bonded with 4-META opaque resin. Many specimensof these groupsshowedcohesiveand cohesive-adhesivefailure. The shearbond strengths after 100,000thermocycles were 28.4 MPa for Ag-Pd-Cu-Au alloy and 20.8MPa for type III alloy. The highest bond strength was obtained with group 14 at thermocycle 0. Group 14 also showeddurability of the bond and 27.4 MPa shear bond strength was maintained after 100,000cycles. The debonded surfacesof group 14, however, displayed adhesivefailure in all conditions. The decrease in bond strength calculated from the strength after thermocycles 0 and 100,000 were 60.2% (group 12), 20.9% (group 13), 35.2% (group 14), 71.3% (group 22), and 37.9% (group 23). Fig. 2 shows the comparisonof the bond strengths after 100,000cycles. The results of shear testing after 100,000cycles were statistically analyzed by analysisof variance and the means were comparedwith a Tukey multiple comparisoninterval (Table V). Groups 13 and 12, groups14 and 12, and groups 23 and 22 were statistically different at the p < 0.05 level. The differencesbetweengroups 12and 22 or groups 13and 23 were not statistically significant.

DISCUSSION Some organic compoundswith a mercapto group have shownbonding ability to preciousmetals suchasgold, palladium, and platinum.g However, the use of thiols as an adhesivebonding promoter hasbeendifficult. Thiols cause a chain transfer reaction during propagation of vinyl or acrylic free radicals and considerably affect the degreeof polymerization of the dental acrylic resin adhesives.Moreover, if an acrylic mercaptan such as N-(4-mercaptophenyl)methacrylamide is usedin an acrylic solvent, gelation of the solution occurs during storage.This phenomenonis supposedto be caused by the reaction of the mercapto group and acrylic resin compound in the solution. Kojima et al.l2 found that the VBATDT monomer recrystallized from the mixture of diethyl ether and n-hexane showeda thione structure that did not contain a free mercapto group (Fig. 1). They alsoreported strong bond-

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BONDING

COMPOSITE

RESIN

AND

PRECIOUS

ALLOY

Ag-Pd-Cu-Au VBATDT + WA-TBB VBATDT + 4-META/MMA-TBB Ion-coating

I

+ 4-META/MMA-TBB

Type III gold VBATDT + MMA-TBB VBATDT + I-METAIMMA-TBB I

0

I

I

I

10

20

30

Shear bond strength Fig.

Table

IV.

2.

Comparison

of composite

resin-metal

Type of bond failure Type

bond strengths

after 100,000 thermocycles.

V. Statistical 100,000 thermocycles

Table

of bond

failure

(MPa)

analyses of shear strengths

after

Group

(MPa)

Mean

Cycles Group 11 12 13 14 21 22 23

0

20,000

AAAAA CMMAA CCCMM AAAAA AAAAA MAAAA CMMMMCCMMM

AAAAA AAAAA MMMMA AAAAA AAAAA AAAAA

60,000 AAAAA AAAAA MMMMA AAAAA AAAAA AAAAA MMAAA

100,000

AAAAA MMAAA AAAAA AAAAA AAAAA

Ag-Pd-&-Au Type

III alloy

13 14 12

28.4* 27.4* 14.0**

23 22

20.8* 9.1*

VBATDT

+ no-4-META

12 22

14.0 9.1

VBATDT

+ 4-META

13

28.4

23

20.8

A, Adhesive failure at the opaque resin-metal interface; C, cohesive failure within the opaque resin; M, mixture of cohesive failure and adhesive failure.

*Asterisks

ing of an MMA-TBB resin to precious metals with the use of VBATDT primer, and speculated that the strong bonds and acceptable shelf life of the primer solution were derived from a possible thiol-thione tautomeric structure of the VBATDT monomer. As seen in Tables II and III, the VBATDT primer was effective in bonding composite and precious alloys. However, the use of 4-META/MMA-TBB opaque resin together with VBATDT primer was essential to achieve durability of the bond. The adhesive bonding durability of light-activated opaque resins was insufficient compared with that of 4-META/MMA-TBB opaque resin, even if the precious alloys were primed with VBATDT. The results of group 11 and 12 show the difference between 4-META and VBATDT as metal adhesive promoters. The 4-META resins strongly bonded to dental base metal alloys because the monomer showed affinity to the metal oxides such as chromium oxide, tin oxide, and copper oxide. However, the amount of metal oxide on the pre-

cious alloy surfaces may be too small for 4-META monomer to bond with precious alloys. The VBATDT monomer contains a thione or thiol structure. It has been reported that if a free mercapto group exists around the resin-precious metal interface, the mercapto group reacts with palladium to form a chemical bond. The evidence of a metalsulfur bond was detected by electron spectroscopy for chemical analysis.g The difference between group 11 and 12 may be ascribed to the reactivity of the monomers to the precious metal elements. As seen in Table III, nearly the same result was obtained from gold alloy. The use of the 4-META monomer together with VBATDT primer did not affect the bond strength, but reciprocally enhanced the bond strength (groups 13 and 23). These results suggest that the use of VBATDT primer together with 4-META/MMA-TBB resin presents no problem in practice or in laboratory procedure as long as the VBATDT has been primed before the application of 4-META resin.

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

in the same column show significantly

different

groups (p < 0.05).

ATSUTA,

The results with ion-coated specimens were also acceptable, but the debonded surfaces showed adhesive failure in all instances. The bond between 4-META resin and the copper oxide layer was strong, but the strength of the copper oxide layer itself may be weaker than that of an untreated precious metal surface. The applicat.ion of VBATDT primer and 4-META/ MMA-TBB opaque resin considerably improved the bond between composite resin and precious alloys without the need for complicated surface preparations of the metal frameworks. Mechanical retentive devices on the cast precious metals can be reduced by using this method. The leakage from the alloy-opaque resin interface may also be decreased. CONCLUSIONS Adhesive bonding between a light-cured fixed prosthodontic composite resin and precious metal alloys was investigated with the use of a metal primer and an adhesive opaque resin. Shear bond strengths after numerous thermocycles were determined to examine the durability of the bond. A metal primer that contained 6-(4-vinylbenzyl-npropyl) amino-1,3,5-triazine-2,4-dithiol (VBATDT) and 4-META/MMA-TBB opaque resin effectively bonded light-cured composite and Ag-Pd-Cu-Au alloy or type III gold alloy. The surface preparations of the metal frameworks such as heating, plating, and ion-coating would no longer be necessary except for minimum retentive devices and alumina sand-blasting. This method may be useful to make composite resin veneered prostheses that must stand up under long use. REFERENCES 1. Musil R, Tiller HJ. Die molekulare Kopplung der Kunststoff-Verblendung an die Legierungsoberflache. Dent Labor 19&1;32:1155-61. 2. Barzilay I, Myers ML, Cooper LB, Graser GN. Mechanical and chemical retention of laboratory cured composite to metal surfaces. J PROSTHET DENT 1988;59:131-7. 3. Naegeli DG, Duke ES, Schwartz R, Norling BK. Adhesive bonding of

300

composites

to a casting

alloy.

MATSUMURA,

J PROSTHET

DENT

AND

TANAKA

1988;60:279-83.

4. Tanaka T, Nagata K, Takeyama M, Atsuta M, Nakabayashi N, Masuhara E. 4.META opaque resin-a new resin strongly adhesive to nickel-chromium alloy. J Dent Res 1981;60:1697-706. 5. Matsumura H, Varga J, Masuhara E. Composite type adhesive opaque resin. Dent Mater J 1986;5:83-90. 6. Matsumura H, Nakabayashi N. Adhesive 4-META/MMA-TBB opaque resin with poly(methy1 methacrylate)-coated titanium dioxide. J Dent Res 1988;67:29-32. I. Yoshida K, Matsumura H, Atsuta M. Monomer composition and bond strength of light-cured I-META opaque resin. J Dent Res 1990;69%4951. 8. Shigeto N, Kawazoe Y, Hamada T, Yamada S. Adhesion between copper-plated acrylic tray resin and a polysulfide rubber impression material. J PROSTHET DENT 1979;42:228-30. 9. Kojima K. Studies on adhesion of functional monomers with SH group to tooth substrates and dental alloys. J Jpn Dent Mater 1986;5:92-105. 10. Mori K, Asabe N, Nakamura Y. Study of triazine thiols. III. Preparation of triazine thiol-containing polymers. J Polym Sci Polym Lett Ed 1982;20:321-7. 11. Mori K, Nakamura Y. Study on triazine thiols. V. Polymerization of 6-(4-vinylbenzyl propyl)amino-1,3,5-triazine-2,4-ditbiol on copper plates and their corrosion resistance. J Polym Sci Polym Lett Ed 1983;21:889-95. K, Kadoma Y, Imai Y. Adhesion to precious metals utilizing 12. Kojima triazine dithione derivative monomer. J Jpn Dent Mater 1987;6:702-7. 13. Nakabayashi N, Masuhara E, Mochida E, Ohmori I. Development of adhesive pit and fissure sealants using a MMA resin initiated by a trin-butyl borane derivative. J Biomed Mater Res 1978;12:149-65. 14. Takeyama M, Kashibuchi S, Nakabayashi N, Masuhara E. Studies on dental self-curing resins. 17. Adhesion of PMMA with bovine enamel or dental alloys. J Jpn Sot Dent Appar Mater 1978;19:179-85. 15. Matsumura H, Kawahara M, Tanaka T, Atsuta M. Surface preparations for metal frameworks of composite resin veneered prostheses made with an adhesive opaque resin. J PROSTHET DENT (accepted) 16. Tanaka T, Hirano M, Kawahara M, Matsumura H, Atsuta M. A new ion-coating surface treatment of alloys for dental adhesive resins. J Dent Res 1988;67:1376-80. 17 Matsumura H, Kawahara M, Tanaka T, Atsuta M. Bonding of veneering resin and dental alloy with I-METAIMMA-TBB opaque resinadhesive durability of surface treated Au-Ag-Pd alloy. J Jpn Prosthodont Sot 1988;32:1306-10. Reprint requests to: DR. MITSURU ATSUTA DEPARTMENT OF FIXED PROSTHODONTICS NAGASAKI UNIVERSITY SCHOOL OF DENTISTRY 7-1, SAKAMOTO-MACHI, NAGASAKI-CITY, 852 JAPAN

MARCH

1992

VOLUME

87

NUMBER

3

Bonding fixed prosthodontic composite resin and precious metal alloys with the use of a vinyl-thiol primer and an adhesive opaque resin.

Adhesive bonding of a light-cured fixed prosthodontic composite resin joined to silver- and gold-based alloys was investigated with the use of a metal...
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