Bonding of dental porcelain to ceramic-metal alloys

BARGHI,

5. 6.

7.

8.

9.

10.

Il.

12.

13.

Anthony DH, Burnett DL: Shear test for measuring bonding in cast gold-alloy-porcelain systems. J Dent Res 49:27, 1970. Kelly M, Asgar K, O’Brien WJ: Tensile strength determination of the interface between porcelain fused to gold. J Biomed Mater Res 33403, 1969. Shell JS, Nielsen JP: Study of the bond between gold alloys and porcelain. J Dent Res 41:1424, 1962. Cascone PJ: The Theory of Bonding for Porcelain-to-MetalSystem. The State of the Art. Berkeley, 1977, University of California, School of Dentistry, p 109. Silver M, Klein G, Howard MC: Evaluation and comparison of porcelain-fused-to-cast metals. J PROSTHET DENT 10~1055, 1960. Leone EF, Fairhurst CW: Bond strength and mechanical properties of dental porcelain. J PROSTHET DENT 18~155, 1967. Lacy AM: The Chemical Nature of Dental Porcelain. The State of the Art. Berkeley, 1977, University of California, School of Dentistry, p 47. McLean JW: Physical and Chemical Characteristics of Alloys Used for Ceramic Bonding. The State of the Art. Berkeley, 1977, University of California, School of Dentistry, p 79. Warpeha Jr WS, Goodkind RJ: Design and technique variables affecting fracture resistance of metal-ceramic restorations. J PR~STHET DENT 35:291. 1976.

Bonding

of dental porcelain

Elina K. Uusalo,

D.D.S.,*Veijo

University

Institute

of Turku,

P. Lassila, D.M.P.,**

of Dentistry,

Turku,

14.

15.

16.

17.

18. 19.

26

of Prosthetics. of Prosthetics. of Prosthetics.

ARANDA

Reprint requests to: DR. NASSER BARCHI UNIVERSITY OF TEXAS HEALTH DENTAL SCHOOL SAN ANTONIO. TX 78284

SCIENCE CENTER

to ceramic-metal and Antti

U. Yli-Urpo,

alloys D.M.P.+**

Finland

eramic-metal restorations are abrasion resistant, color stable, and insoluble in oral fluids. However, certain physical and chemical requirements must be fulfilled to obtain good bonding between porcelain and metal. The significance of oxides and Van der Waal’s forces for bonding was reported by Shell and Nielsen.’ The presence of oxygen or air during firing was found to improve the bonding, supporting the theory that bonding has a chemical nature.2,3 Impurity in gold also seems to improve bonding, again indicating a chemical system.4 Bond strength was decreased when the alloy was coated with pure gold.5 Several coating agents have been offered to improve the bond strength of porcelain to metal, but the results have not been significant.6 The significance of

Lecturer, Department Professor, Department Lecturer, Department

AND

Mackert Jr JR, Parry EE, Hashinger DT, Fairhurst CW: Measurement of oxide adherence to PFM alloy J Dent Res 63:1335, 1984. O’Brien WJ, Kring JE, Ryge G: Heat treatment of alloys to be used for the fused porcelain technique. J PROSTHET DENT 14:955, 1964. Pask JA: Fundamentals of wetting and bonding between ceramics and metals. In Valega TM, editor: Alternatives to Gold Alloys in Dentistry. DHEW Publication No. (NIH) 77-1227, 1977, p 235. Barlow FL: A Point Identification Loading Study of Two Ceramo-Metal Systems Related to Porcelain Thickness, Repeated Firings and Surface Conditions. Masters degree thesis, University of Minnesota, 1976. King BW, Tripp HP, Duckworth WH: Nature of adherence of porcelain enamels to metals. J Am Ceram Sot 42504, 1959. McLean JW: The Art and Science of Dental Ceramics. New Orleans, Louisiana State University, School of Dentistry, Continuing Education Program, 1974.

C

*Assistant **Assistant ***Senior

WHITMER,

0 0

1 mm {

@3

7

-mm

mm6 0

Fig. 1. Schematic figure of test specimen.

the oxide layer for bonding was demonstrated by several investigators.7A’0 Bonding is also influenced by the thermal expansion coefficient of the materials, the microstructure, and the grain size of the alloys.3~4~‘o-‘3

JANUARY

1987

VOLUME

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NUMBER

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BONDING

OF DENTAL

PORCELAIN

TO CERAMIC-METAL

ALLOYS

Table I. Material Material Jelenko 0 MK 1 LM-Ceragold LM-Ceragold Wirobond Rx Biocast Wiron 77

Manufacturer

Type

2 (MK 4

2)

Gold alloy Gold alloy Gold alloy Gold alloy Cobalt-chromium Cobalt-chromium Nickel-chromium

J.F Jelenko, New Rochelle, N.Y. Outokumpuoy, Pori, Finland Outokumpuoy Outokumpuoy Bego, Bremen, West Germany Rx Jenerix, Wallingford, Conn. Bego

In addition to bonding of porcelain to gold alloys, bonding to semiprecious and nonprecious alloys has given good results.‘4, ” However, roughness of the surface appears to effect large differences in bond strength.15 Several technical laboratory procedures, such as drying the porcelain, condensation, firing, and handling the alloy surface, have an effect on bond strength and fracture durability.13, 16,17 The bond strength of porcelain to metal was studied by many methods. The first shear test was developed by Shell and Nielsen.’ Others have used this test or a modification of it.2, 4-6,13,” Nally and Berta’” and NallyzO studied the bonding of porcelain to an alloy by a pull test with a tensometer and by a pressure test. The results of the shear test method developed by Schmitz and Schulmeyer2’ differed from the others, since it seemed to show the quality of the porcelain rather than the bonding capacity.13 This study compared the bond strength of porcelain fused to metal in four gold and three nonprecious alloys by a simplified shear test method. MATERIAL

AND

METHODS

Seven alloys were used as test metals (Table I): four gold and lhree nonprecious alloys, ail commercially available. The porcelain used in the test was Biodent (De Trey Gesellschaft mbH, Wiesbaden, West Germany). The specimens for the pull test (Fig. l), six to 10 of each alloy, were cast according to the manufacturers’ instructions. Each specimen consisted of a round test surface, 7 mm in diameter, and a fastening ring for the pull test procedure. The test surfaces were fused as follows: The surfaces were sandblasted and washed in boiling distilled water for 20 minutes. Oxidation was performed by heating the specimens at 990” C for 10 minutes without vacuum. The test surfaces were veneered by a bonding agent (GUH, Biodent, De Trey Gesellschaft mbH) and fused under vacuum at 990” C for 2 minutes separately for each specimen. Thereafter the specimens were fused together in couples with a thin layer of ground mass (GUH, Biodent) between the surfaces, at 990” C, for 2

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

Gold and metals platinum group

Color Yellow Yellow White White

Table II. Bond strength Values strength

Alloys Jelenko 0 MK 1 LM-Ceragold LM-Ceragold Wirobond Rx Biocast Wiron 77

2 4

162.0 77.3 138.2 101.0 93.5 74.8 89.6

of

978 962 845 935

and fracture of bond (pull test) ? t ? + k k k

39.5 15.6 26.2 20.7 32.8 14.5 35.9

lines Fracture line* (range) 3-3 2-2 3-3 3-2 2-2 l-l 3-2

$1 = About one half of the metal surfaces were exposed; 2 = metal surfaces were exposed as patches; 3 = fractured surfaces were covered by a uniform layer of porcelain.

minutes, under vacuum, and according to the recommended instruction. For the test of the bond strength, the alloy specimens were fastened to the test machine (Type FM 1000, WEB Thuringer, Industriewerk Rauenstein). The pulling speed was 8 mm/min. The load was applied until the test specimens sheared off. The bond strength value was calculated and the fracture surfaces were analyzed and photographed. RESULTS The bond strength values for each alloy are seen in Table II. For the gold alloys the bonding capacity was generally good. The highest value was measured for Jelenko 0. The value for LM-Ceragold 2 was almost at the same level, but the bond strength values for LMCeragold 4 and MK 1 were somewhat lower. In all gold alloys the fracture lines between the test surfaces were located mainly inside the porcelain (Fig. 2 and Table II). For the nonprecious alloys the bond strength values were generally lower and the standard deviations were on the average higher than for the gold alloys. In the nickel-chromium alloy, however, the fracture line was also mainly located inside the porcelain (Table II). In the cobalt-chromium alloys the test surfaces were more

27

UUSALO,

LASSILA,

AND

YLI-URPO

tively high, but this is normal in a test of this type.5a’5,‘8 The simplified test method usedseemedto be acceptable for a laboratory study of porcelain-metal combination. In the nonpreciousalloys the lower bond strength and the different fracture lines are thought to be due to the physical properties of these alloys, such as thermal expansion, the rigidity of the surface, or the technical laboratory procedures.The good resultsobtained earlier with nonprecious alloyst4,” seem to demonstrate the importance of laboratory procedures.

SUMMARY

Fig. 2. Fractured surfaces after bond strength test. Fracture line is located inside porcelain (Ceragold 4).

AND

CONCLUSION

The bond strength of porcelain to the four gold alloys and the three nonprecious alloys was tested with a simplified pull test method, having wide test surfaces. The testsshowedthat all gold alloys testedwere suitable for fusing porcelain. The bond strength in nonprecious alloys was somewhat lower and the location of the fracture lines was more variable. It seemsthat nonprecious alloys are more sensitiveto laboratory procedures. The bond strength and the location of the fracture line had a good correlation in all metal alloys. REFERENCES 1. 2.

3. 4.

Fig. 3. Fracture line is partly juncticn (Rx Biocast).

located

at metal-ceramic

5.

6.

or lessexposed after the shear test (Fig. 3). The bond strength and the location of the fracture line correlated well in both alloys.

7.

DISCUSSION

8.

Because of differences in the direction of shear strength and in the shape, size, and thickness of the porcelain layer usedin the test, the results are not easily comparable with those obtained by other test meth&

10.

1,13,19,21

The test seemedto show real bond strength and maximum power was measuredwhen the fracture line was completely located in the porcelain. The results were affected by the large size of the test surfaces comparedwith the thicknessof the porcelain layer. The location of the fracture lines always varied according to the alloy, but in general correlated well with the bond strength. Standard deviations of the results were rela-

28

9.

11.

12.

13.

14.

Shell JS, Nielsen JP: Study of the bond between gold alloys and porcelain. J Dent Res 41:1424, 1962. Leone EF, Fairhurst CW: Bond strength and mechanical properties of dental porcelain enamels. J PR~STHET DENT 18:155, 1967. Lautenschlager EP, Greener EH, Elkington WE: Microprobe analyses of gold-porcelain bonding. J Dent Res 42:1206, 1969. Vickery RC, Badinelli LA: Nature of attachment forces in porcelain-gold system. J Dent Res 47:683, 1968. Anthony DH, Burnett AP, Smith DL, Brooks MS: Shear test for measuring bonding in cast gold alloy-porcelain composites. J Dent Res 49:27, 1970. Goeller I, Meyer JM, Nally JN: Comparative study of three coating agents and their influence on bond strength of porcelainfused-to-gold alloys. J PROSTHET DENT 28~504, 1972. Nally JN, Meyer JM: Recherche exfierimentale sur la nature de la liaison &ram+metallique. Schweiz Monatsschr Zahnheilkd 80:250, 1970. Meyer MJ, Nally NK: Chemical bonding in the porcelainbaked-to-metal technique. J Dent Res 50:760, 1971. Espevik S, @lo G, Lodding A: Oxidation of noble metal alloys for porcelain veneer crowns. Acta Odontol Stand 37:323, 1979. Dent JR, Preston JD, Moffa JP, Caputo A: Effect of oxidation on ceramo-metal bond strength. J PROSTHET DENT 4759, 1982. Asgar K, Giday Z: Behavior of ceramic noble metals containing no silver with porcelain. J Dent Res 58 (Special issue) A:688, 1979. Johansson B, Espevik S: Microstructure and chemical composition of noble alloys for porcelain veneering. Swed Dent J 2:35, 1978. @lo G, Johansson B, Syverud M: Bond strength of porcelain to dental alloys-An evaluation of two test methods. Stand J Dent Res 89:289, 1981. Moffa JP, Lugassy AA, Gucks AD, Gettelman L: An evaluation

JANUARY

1987

VOLUME

57

NUMBER

1

BONDING

15.

16. 17. 18. 19.

OF DENTAL

PORCELAIN

TO CERAMIC-METAL

ALLOYS

of nonprecious alloys for use with porcelain veneers. Part 1. Physical properties. J PROSTHET DENT 30~424, 1973. Luhovich RP, Goodkind RJ: Bond strength studies of precious, semiprrcious and nonprecious ceramic-metal alloys with two porcelair,s J PRO~THET DENT 37~288, 1977. Yli-Urptl A: Investigation of a dental gold alloy and its ceramic bonding. .2cta Odontol Stand 33(suppl 69):59, 1975. Phillips RW: Skinner’s Science of Dental Materials, ed 8. Philadelphia. 1982, WB Saunders Co, pp 502-530. hla1hotr.t XfL. hlaichel LB: Shear bond strength in porcelainrnelai restorations J PROSTHET DENT 43:397, 1980. Nab) JN. Berm j J: Recherches experimentales sur les propri&t&s mec~niques des ciramiques cuites sur alliges. Monatsschr Zahnheilkd 75:93 1965.

Saliva contamination metal retainers Andrew

J. Cassidy, D.D.S.,*

Ft.

Tex.

Hood,

and David

*Major, U.S. )Irmy Dental Corps, Senior Resident, General Dentistry Residency; presently U.S. Army Dental Clinic, Bad Hersfeld. **Colonel, Uj. Army Dental Corps; Chief, Fixed Prosthetics.

OF PROSTHETIC

DENTISTRY

Reprint requests to: DR. V. P. LASSILA UNIVERSITY OF TURKU INSTITUTE OF DENTISTRY LEMMINKAISENKATU 20520 TURKU 52

2

FINLAND

of etched

Q. Storie, D.D.S.**

ne of the inconveniences of the “Maryland bridge technique” is the delay produced by the etching process after the try-in and before final insertion. When the laboratory etches the metal, three appointments are necessary for completion of an etched-metal resinretained fixed partial denture (FPD): (1) for tooth preparation and impression making, (2) for try-in and adjustment, and (3) for final insertion. If the etched metal surface could be protected from contamination during the try-in and adjustment period, many etchedmetal fixed partial dentures could be completed in two appointments. The most obvious method for protecting the etched-metal surface from contamination would be to apply the unfilled resin to the retainer and allow its complete polymerization before trying the fixed partial denture in the mouth. The retentive strength of the etched-metal FPD depends on three different bonds; (1) resin-to-enamel bond, (2) cohesive bond of the composite, and (3) resin-to-etched metal bond. Of these, the resin-to-enamel bond is the ‘
JOURNAL

21.

Nally JN: Chemico-physical analysis and mechanical tests of the ceramo-metallic complex. Int Dent J 18~309, 1968. Schmitz K, Schulmeyer H: Bestimmung der Haftfestigkeit dental metallkeramischer Verbundsysteme. Dent Labor 231416, 1975.

and resin bonding

0

THE

20.

mately 3960 psi.’ Exposing a layer of unfilled resin to saliva during the try-in before adding more composite (as in final insertion) would be testing the strongest link in the etched-metal resin-retained system. The purpose of this study was to evaluate the effect of preinsertion application of unfilled resin and subsequent saliva contamination on the retention of etched-metal retainers.

MATERIAL

AND

METHODS

Ninety 10 mm X 10 mm X 0.5 mm metal retainers were made with Lite Cast B (Williams Gold Refinning Co Inc., Buffalo, N.Y.). Each retainer was etched at 200 ma/cm2 for 6 minutes in 10% sulfuric acid with methanol by using a Time etch machine (Time Dental Products, Baltimore, Md.). Each retainer was then cleaned ultrasonically in 18% hydrochloric acid for 10 minutes, washed under tap water, and dried by air syringe. Retainers were examined at Xl0 under a phase contrast microscope (Unitron Scientific, Inc., Newton Highlands, Mass.) for quality of etch (Fig. 1). Retainers of poor quality were reetched. The 90 retainers were then randomly divided into three equal groups. Retainers in group No.1, numbers 1 to 30, had a thin layer of Comspan (L.D. Caulk Co., Milford, Del.) bonding agent applied to the etched metal surface with a fine nylon brush. Immediately a resin core was made by injecting Comspan paste (filled resin) from a syringe into

29