Adhesive performance of permanent 3D-printed restorative materials and a CAD/CAM composite block following various surface treatments and resin cement strategies

The growing use of permanent 3D-printed restorative materials has increased the need for evidence-based bonding protocols. This study evaluated the bonding performance of three permanent three dimensional (3D)-printed restorative materials and a computer-aided design and computer-aided manufacturing (CAD/CAM) composite block following different surface treatment and cementation strategies. Three permanent 3D-printed restorative materials (Saremco Crowntec, VarseoSmile Crown Plus, and Formlabs Permanent Crown) and one CAD/CAM composite block material (Grandio CAD) were subjected to five surface treatment protocols: no treatment, hydrofluoric acid etching, laser irradiation, tribochemical silica coating (CoJet), and Al₂O₃ airborne-particle abrasion. Bonding was performed using either a light-cure resin cement (G-Cem Veneer-AD1) or a dual-cure resin cement (RelyX U200-AD2). Microtensile bond strength values were analyzed using 3-way ANOVA, Games-Howell test were used. (α = 0.05). Surface treatment, restorative material, and resin cement significantly affected µTBS (all p < 0.001). Significant interactions were observed for surface treatment × material ( p < 0.001), surface treatment × cement ( p = 0.003), and surface treatment × material × cement ( p < 0.001), whereas the material × cement interaction was not significant ( p = 0.710). The highest mean µTBS was observed for Formlabs treated with CoJet and bonded with AD1(42.07 ± 8.60 MPa), whereas the lowest was recorded for Formlabs treated with hydrofluoric acid and bonded with AD1 (11.93 ± 4.53 MPa). The effectiveness of surface treatment therefore varied according to the specific material–cement combination. Bond strength of digitally fabricated restorative materials was significantly influenced by surface treatment, manufacturing technique, and resin cement type. Mechanical surface treatments improved bonding performance; however, the optimal protocol was material dependent.