Influence of the bonder on the adhesion of porcelain to machined titanium as determined by the strain energy release rate.

OBJECTIVE: To determine the adhesion at the titanium-porcelain interface using a fracture mechanics approach, and to investigate the bonding mechanism using SEM. METHODS: Specimens of five different titanium-porcelain and one base metal-porcelain bonding systems were prepared for a four-point bending interfacial delaminating test on a universal testing machine. The pre-cracked specimen was subjected to load and the strain energy release rate (G, J/m(2)) was calculated from the critical load to induce stable crack extension in each system. The interface for the various materials was investigated in an SEM and compared. RESULTS: The titanium-porcelain with Gold Bonder showed the highest G-value (72.39+/-13.21J/m(2)) among the groups whilst titanium-porcelain with cross-cut-bur preparation showed the lowest (5.78+/-1.39J/m(2)). The former was significantly higher than that of Wiron 99 (base-metal, BEGO, Germany) porcelain (40.01+/-6.67J/m(2)), a clinically accepted bonding system for many years. The G-values of porcelain fused to titanium-Rocatec, titanium-sandblasted and/or titanium-GC-Bonder were 10.81+/-1.49, 12.64+/-3.01 and 35.74+/-5.20J/m(2), respectively. SEM images of the interface fracture crack path for the different bonders enabled the mechanisms responsible for the differences in strain energy release rates to be appreciated. CONCLUSION: The strain energy release rate (G) of titanium-porcelain with a Gold Bonder interface layer was highest among the five different systems.