Repair of silorane composite—Using the same substrate or a methacrylate-based composite?

Objective The study aimed to analyze the shear bond strength of aged silorane composite repaired with the same substrate or a conventional methacrylate-based composite after different mechanical and adhesive surface treatments. Methods Silorane composite specimens were aged by thermal cycling (5000 cycles, 5-55 °C) and randomly assigned to different surface treatments (each group n=16): diamond bur abrasion, aluminum oxide sandblasting, silica coating, or hydrofluoric acid etching. Then, an adhesive system corresponding to the repair composite or a combination of silane agent and the respective adhesive was applied. Silorane composite or a nanofiller composite were adhered onto the conditioned surfaces. In the control group (n=16), silorane composite was adhered to fresh substrate (incremental build up). After further thermal cycling, shear bond strength was tested and failure modes were assessed. Data were analyzed by ANOVA/post hoc tests, Weibull statistics and Chi(2)-test (p≤0.05). Results Incremental shear bond strength (control group: 21.0±10.5 MPa) was achieved by all groups except those etched with hydrofluoric acid or samples abraded with diamond bur and repaired with the nanofiller composite without silane application. Generally, the application of the silane agent improved repair bond strength of the nanofiller but not of the silorane composite. Cohesive failure was observed more frequently than adhesive failure when the silane agent was applied or when silorane composite was used for repair. Significance Silorane composite can be repaired with either the same substrate or a methacrylate-based nanofiller composite but requires mechanical surface treatment and--in case of the methacrylate-based composite--silanization prior to adhesive application.