Metal ceramic bond after multiple castings of base metal alloy.
BACKGROUND
Remelting previously cast metal can produce a critical change in metal-oxide composition at the dental alloy surface.


OBJECTIVE
The purpose of this study was to evaluate the effect of multiple castings on bonding of a single selected base metal and a dental ceramic, and to compare results from shear bond and 3-point-bending tests.


METHODS
Three groups of dental alloy (Remanium CSe) were prepared by mixing 50% fresh alloy to alloy remnants from previous castings. The specimens in the first casting group used 100% fresh alloy and served as control (C0). The second group consisted of equal amounts of fresh alloy and alloy remnants cast only once (C1). The third and fourth groups contained 50% fresh alloy and alloy cast twice (C2) and 3 times (C3), respectively. The bond load (N) between alloy and dental porcelain (VMK 95 Metal Ceramic) was evaluated, using shear bond and 3-point bending tests. The fracture surfaces of the specimens subjected to testing were analyzed using a stereomicroscope and scanning electron microscope. One-way ANOVA followed by the Tukey multiple comparison test was used for analysis of bond data (alpha=.01).


RESULTS
The mean shear bond load (SD) of C0 (738.0 (77.1) N) was significantly higher than that of C1 (577.8(139.4) N), C2 (494.8 (77.6) N), and C3 (480.5 (60.9) N). Mean peak load for the 3-point-bending test of specimens cast from C0 (39.8 (1.79) N) was significantly higher than for other groups (P<.01). No significant difference was found between C1 (24.4 (5.60) N), C2 (23.2 (4.03) N), and C3 (22.8 (1.79) N) in terms of the shear bond test and the 3-point bending test.


CONCLUSIONS
In general, there was agreement between the 2 bond strength tests to indicate that including re cast base alloy with fresh alloy for metal decreases metal-to-ceramic bond strengths. (J Prosthet Dent 2009;102:165-171)
Ucar
Yurdanur
Y
Department of Prosthetic Dentistry, College of Dentistry, Cukurova University, Adana, Turkey. ysanli@cu.edu.tr and yurdanursanli@yahoo.com
Aksahin
Zafer
Z
Kurtoglu
Cem
C
D003722:Dental Alloys / Q000737:chemistry*; D001840:Dental Bonding; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000295:instrumentation / Q000379:methods; D017743:Equipment Reuse; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D033081:Shear Strength
D003722:Dental Alloys; D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys