Recasting of Base Metal Alloys and its Effect on Metal Ceramic Bond Strength
ZC28-ZC32
Correspondence
Dr. Sandeep Garg,
Professor and Head, Department of Prosthodontics including Crown and Bridge, Maharishi Markandeshwar College of Dental Sciences and Research (MMCDSR), Mullana, Ambala-133207, Haryana, India.
E-mail: drsgargmmu@gmail.com
Introduction: A steep rise in the cost of noble metals leads to use of base metal alloys, due to their low cost, good mechanical properties and low density. It would be economically advisable to use fresh alloy in combination with reuse alloy, to reduce the cost of fixed partial dentures.
Aim: To evaluate the effect of recasting of Nickel-Chromium (Ni-Cr) and Cobalt-Chromium (Co-Cr) base metal alloys on the metal ceramic flexural bond strength.
Materials and Methods: This in-vitro study was conducted in the Department of Prosthodontics, Crown and Bridge of Maharishi Markandeshwar College of Dental Sciences and Research, Mullana, Ambala, Haryana, India in October 2020. A total of 60 specimens were fabricated using Ni-Cr and Co-Cr metal alloys (n=30). Different proportions of new and old Nickel-Chromium (Group A) and Cobalt-Chromium (Group B) base metal alloys were used to fabricate the specimens i.e., Control subgroup A0/ B0 (100% new alloy), subgroup A1/B1 (50% new alloy and 50% remnants from subgroup A0/B0), subgroup A2/B2 (50% new alloy and 50% remnants from subgroup A1/B1). Ceramic was applied in the centre of each prepared metal specimen in the dimension of 8×3×1 mm. All specimens were subjected to three point bending test in Universal Testing Machine (UTM) till failure occurred and values were recorded. Statistical analysis was carried out using Statistical Package for the Social Sciences (SPSS) software version 17.5. Data obtained was compiled and analysed using one-way Analysis of Variance (ANOVA), Post-hoc tukey’s and Student t-tests. The p-value <0.05 was considered as statistically significant.
Results: In Group A (Nickel-Chromium) and Group B (CobaltChromium), maximum flexural bond strength was observed in subgroup A0, B0 (control subgroup) followed by subgroup A1, B1 whereas minimum was observed in subgroup A2, B2. A highly significant difference (p-value <0.001) in flexural strength was observed among all the subgroups. Metal ceramic bond strength observed in Group A (Ni-Cr) was higher than the metal ceramic bond strength observed in Group B (Co-Cr) in all the subgroups. This difference was statistically significant in subgroup 0 and subgroup 1 equal variances assumed (p-value=0.023), whereas no significant difference was observed in subgroup 2 with equal variance assumed (p-value=0.058).
Conclusion:From the present study, it can be suggested that recasting of base metal alloys should be avoided, since it causes significant reduction in metal ceramic bond strength.