Weibull parameters of composite resin bond strengths to porcelain and noble alloy using the Rocatec system

Objective: The aim of the study was to determine the Weibull distribution parameters S0 and m of the tensile bond strength of a composite resin sandwiched between a noble metal alloy and a feldspathic porcelain using the Rocatec system. Methods: Specimens were prepared either as Au-Pt-Pd alloy cylinders alone or as alloy cylinders and a feldspathic porcelain. Surface treatments included 110 μm Al2O3 sandblasting (Rocatec Pre), tribochemical silica coating (Rocatec Plus) and silane application (ESPE-Sil) prior to composite bonding. The tensile bond strengths of ceramic-resin-ceramic and metal-resin-metal specimens were determined before and after thermocycling at 5–60°C for 1000 cycles. Statistical analyses were conducted using two parameter Weibull distributions determined by the characteristic strength (S0) at the 63% probability of failure, the Weibull modulus (m) and the 95% confidence intervals. Results: With respect to the control group (no Rocatec) (7.5 MPa), the Rocatec system significantly augmented the characteristic tensile bond strength S0 of metal (17–18 MPa) and porcelain (20–28 MPa) groups. Thermocycling had no effect on the tensile bond strength of the metal samples and increased (not significant) the bond of the porcelain group. The Weibull modulus m for all groups ranged from 2.8 to 3.7. Significance: This study confirmed the efficacy of the Rocatec system for bonding composite resin to metal or ceramic substrates. However, the variability of the strength of the bond is shown in the low Weibull modulus values obtained. This reflect the difficulties in controlling flaw formation and warrants research for future improvement.