Shear bond strength of provisional restoration materials repaired with light-cured resins

This study evaluated the repair bond strengths of light-cured resins to provisional restoration materials with different chemical compositions and polymerization techniques. Fifty discs (10 mm in diameter and 1.5 mm thick) were fabricated for each provisional resin base material, including a self-cured methacrylate (Alike), self-cured bis-acrylate (Protemp 3 Garant), light-cured bis-acrylate (Revotek LC) and a heat-cured methacrylate (Namilon). All specimens were stored in distilled water at 37 degrees C for seven days before undergoing repair with one of four light-cured resins, including AddOn, Revotek LC, Dyractflow and Unifast LC and a self-cured resin (Alike), according to the manufacturers' instructions, for a total of 200 specimens. After 24 hours of storage in 37 degrees C water, the shear bond strengths were measured with a universal testing machine and fracture surfaces were examined under a stereomicroscope. Two-way ANOVA revealed that provisional resin-base material (p<0.001), repair material (p<0.001) and their interactions (p<0.001) significantly affected the repair strength. Tukey's multiple comparisons showed that the lowest bonding strengths were found in specimens of heat-cured methacrylate resin materials repaired with bis-acryl resins, with their failure modes primarily being of the adhesive type. The highest bond strengths were recorded when the provisional resin-base materials and repairing resins had similar chemical components and the failure modes tended to be of the cohesive type.