Effect of Different Surface Treatments and Manufacturing Methods on the Shear Bond Strength of Repaired Resin‐Based Restorations

OBJECTIVE: The aim of this in vitro study was to evaluate the effects of different surface treatments on the shear bond strength of repaired milled and 3D-printed resin restorations. MATERIALS AND METHODS: A total of 84 resin specimens (8 mm diameter, 5 mm height) fabricated using two different methods such as milling (Grandio Disc) and 3D-printing (Saremco Crowntec) were subjected to three surface treatments: silane (control), air abrasion + silane, and laser irradiation + silane. All specimens were subjected to thermocycling (5000 cycles each) before and after the repair protocol which was conducted with a flowable composite, and the shear bond strengths were measured. SEM images were obtained to evaluate the type of failures. Data were analyzed using IBM SPSS V23, and two-way ANOVA analysis was used for comparisons between surface treatments and samples (p < 0.05). RESULTS: Laser irradiation yielded the highest bond strength (7.61 ± 1.94 MPa), showing a statistically significant difference (p = 0.001). The 3D-printed resin group exhibited significantly higher bond strengths after all surface treatments compared to the milled group (p = 0.028). Representative SEM observations revealed increased surface irregularity and fracture-surface complexity in laser-treated specimens. CONCLUSION: Laser irradiation is an effective method for improving the bond strength in the repair of both milled and 3D-printed resin restorations. Particularly, 3D-printed resins showed superior repair bond strengths. Silane alone is insufficient; additional micromechanical surface treatments are required for reliable adhesion. CLINICAL SIGNIFICANCE: Mechanical complications can occur with milled and 3D-printed resin restorations, which are increasingly used in indirect restorations, and intraoral repair protocols are becoming a crucial consideration. Determining the most appropriate repair protocol and surface treatment is crucial for the successful repair of these new-generation resin restorations.