Influence of surface treatments and adhesive protocols on repair bond strength of glass-matrix and resin-matrix CAD/CAM ceramics

Objective: To specify the effects of self-etching ceramic primer, Monobond Etch and Prime (MEP), and universal adhesive (UA) on repair bond strength between CAD/CAM blocks and resin composite. Materials and Methods: Vita Mark II (VM), IPS e.max CAD (EMAX), Shofu Block HC (SHC), and Tetric CAD (TET) blocks were sliced and thermocycled. They were divided into four groups according to surface treatments (n = 24): control, sandblasting (AL), hydrofluoric acid etching (HF), and MEP application. SEM analysis assessed surface topography. Subdivided, specimens followed distinct adhesive protocols (n = 12): control (silane + adhesive [SA] or adhesive [A] only for MEP group) and UA. Microshear bond strength (mu SBS) was measured following resin composite repair. Data were analyzed using two-way ANOVA and Tukey tests (p < 0.05). Results: The mu SBS of CAD/CAM blocks was significantly influenced by surface treatment type and adhesive protocol. The highest mu SBS values for each block, considering surface treatment + adhesive protocol, were VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA. Conclusions: Except for EMAX, it was not the adhesive protocol that made the significant difference in bond strength for each CAD/CAM block, but the surface treatment. MEP + UA application on glass ceramics lowered mu SBS values significantly, so it is not recommended in clinical conditions. Clinical Significance: Repair is an essential therapeutic option, particularly in esthetic restorations, to swiftly repair the impaired esthetics caused by fracture. Repair protocol is dependent on the restorative material, and to have a reliable repair bond strength, the following surface treatment and adhesive protocol combinations are recommended for each CAD/CAM block: VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA.