Repairability of an alkasite composite: Shear bond strength after different surface treatments

This study aimed to assess both the repairability of an alkasite composite (base material) and the suitability of an alkasite composite for repairs (repair material) compared to a universal composite used as base and repair material. Different mechanical surface treatments (simulated diamond bur abrasion, air abrasion, silica coating) with or without the additional use of a universal primer were performed. Surface roughness, shear bond strength, and failure modes were assessed. Statistical analysis was performed using ANOVAs, Weibull analysis, and Chi 2 -tests (p < 0.05). The base material and the mechanical surface treatment impacted surface roughness (both p < 0.001). The base material did not impact repair bond strength (p = 0.129). For both base materials, air abrasion and silica coating resulted in increased surface roughness compared to control (p ≤ 0.014). Only the mechanical surface treatment, the use of a universal primer, and the applied repair material impacted repair bond strength (all p < 0.001). Overall, mechanical surface treatment by air abrasion or silica coating, application of a universal primer, and repairs using the alkasite composite had a beneficial effect on shear bond strength. The base material, the mechanical surface treatment, and the use of a universal primer impacted the distribution of failure modes (all p < 0.001). For both base materials, most cohesive failures were identified after air abrasion or silica coating. Also, the application of a universal primer led to a higher proportion of cohesive failures. Within the limitations of the study, alkasite composite restorations are suitable for repairs using an alkasite composite or a universal composite. • Repair of alkasite composite restorations is possible. • Mechanical treatment (air abrasion or silica coating) is recommended. • Application of a universal primer is recommended.