ABSTRACT
Objective:To investigate the effect of degassing and peroxidation on metal-ceramic bonding strength of Pd-Ag alloy. Methods:The metal-ceramic interface of group A (peroxidation)and B (degassing)was investigated under scanning electronic micro-scope(SEM)and energy dispersive spectrum (EDS).The bond strength between metal and ceramics was measured using a three-point bend test according to ISO9693.Results:The formation of nodules on the surface of alloy specimens was observed in both groups by SEM.The nodules on the specimens of group A were more densely than those of group B.The diameter of nodules in group B was 1 .5μm approximately.The interface of the metal-ceramic specimens had a clear transition porcelain layer and no hole or slit was present. The mean bonding strength of group A and B was (45.97 ±3.92)MPa and (49.1 1 ±6.42)MPa respectively(P=0.031 ).Conclu-sion:Degassing can improve metal-ceramic bonding strength of Pd-Ag alloy significantly.
ABSTRACT
The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 oC-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14), VB2D (0.63), PI (1.84) and PD (2.62). Pearson's correlation test (r=0.17) was performed to evaluate of correlation between MCBS and CTE differences. Within the limitations of this study and based on the obtained results, there was no correlation between MCBS and CTE differences for the evaluated metal-ceramic pairs.