How the Repair Bonding Strength of Hybrid Ceramic CAD/CAM Blocks Is Influenced by the Use of Surface Treatments and Universal Adhesives

Abstract

We examined how different methods of surface treatment and different universal adhesives with or without extra silane affected the repair bonding strength of hybrid ceramic CAD/CAM restorations. Cerasmart specimens (n=320) were subjected to thermocycling and assigned to the following surface pretreatment protocols: control, diamond bur (DB), hydrofluoric acid (HF), and tribochemical silica coating (TSC). Half the specimens received a coating of silane, followed by application of the universal adhesives Futurabond M+ (FMU), Tokuyama Universal Bond (TUB), Single Bond Universal (SBU), or Clearfil Universal Bond Quick (CUQ) (n=10). A hybrid composite resin was used to simulate repair; then the specimens underwent further thermocycling. Shear bond strength (SBS) was determined and modes of failure were examined. The TSC-CUQ silane (-) group showed the highest SBS values. The best repairs were obtained when the surface was treated with TSC, with the exception of the DB-TUB silane (-) group. TUB increased SBS more than the other adhesives. Additional silane decreased SBS in the HF-TUB and TSC-CUQ groups, while increasing it in the TSC-TUB and DB-FMU groups (p<0.05).