Shear Bond Strength of Ceramic Orthodontic Brackets to CAD/CAM Provisional Materials: Influence of Surface Treatments and a Novel Adhesive System

Objective: To evaluate the effect of surface treatments and flash-free adhesive on the shear bond strength of ceramic orthodontic brackets to CAD/CAM provisional materials.
Materials and Methods: Specimens (n=160) from each provisional material (CAD-Temp and C-Temp) were categorized into four groups according to the surface treatment methods: C (no surface treatment), HP (37% H3PO4), DB (mechanical roughening by diamond bur) and SB (mechanical roughening by sandblasting). Half of the specimens in each group were bonded to one of the maxillary central incisor ceramic brackets according to the used adhesive system: (APC PLUS or APC Flash-free). All specimens were 5000-times thermocycled before the shear bond strength testing (SBS). Data were analyzed using three-way ANOVA, Tukey’s multiple comparison tests. The adhesive remnant index (ARI) was also evaluated. The level of significance was set at 5% for all statistical tests.
Results: C-Temp significantly recorded higher SBS than CAD-Temp (p<. 001). DB and SB groups utilizing flash-free adhesive significantly recorded higher SBS (P<. 05) compared to other groups in the tested materials. Higher ARI scores were recorded in CAD-Temp and flash-free adhesive.
Conclusions: Bonding of orthodontic brackets to provisional restorations is a challenge for orthodontists in adult comprehensive cases that could be improved by an appropriate material, surface treatments, and adhesive system. Mechanical surface treatments and flash-free adhesive would enhance SBS of ceramic orthodontic brackets to CAD/CAM provisional materials. The higher ARI scores reported with CAD-Temp and flash-free adhesive reduces chair time for excess removal.