Effects of Oxide Layer on the Bonding Strength of Ni-Cr Alloys with Porcelain Ceramics.

The metal-ceramic crown restoration was the most actively used at esthetic restoration for its convenience of forming. Due to constant rise of gold price, non-precious metal such as Ni-Cr alloy have been widely used as metal-ceramic restorations. For easy casting and lower melting point Be was added as minor component to Ni-Cr for a long time, but the use of Be was regulated to deteriorate to human lung. In this study, Ni-Cr specimens containing Be (T-3, Ticonium, USA) and non-Be (Bellabond Plus, BEGO, Germany) were fabricated and by heat treatments at 800-1050 0C oxide layer was formed for subsequent bonding to porcelain ceramics. By heat treatment of the non-Be specimens at high temperature more thick oxide layer was formed and showed lower bonding strength due to the debonding at oxide layers. But in the Be-containing specimens debonding was occurred at porcelain layer so that they showed higher bonding strength. So by heat treatment of non-Be specimens at vacuum condition rather thinner oxide film could be formed so that showed higher coupling strength due to the debonding at porcelain layers than oxide layers.