The Effect of Repair Materials and Surface Treatments on the Shear Bond Strength of 3D-Printed Provisional Restoration

Objective Despite the emergence of numerous three-dimensional (3D) printed provisional resin, there are no conclusive guidelines for repairing them. This study aims to investigate the effects of different repair materials and surface treatments on the shear bond strength of 3D-printed provisional resin. Materials and Methods A total of 180 3D-printed resin specimens underwent six surface treatments: no surface treatment (control), silicon carbide paper (SP), sandblasting with aluminum oxide (SB), SP followed by SB (SP + SB), SP with bonding agent (SP + BD), and SB with bonding agent (SB + BD). Each group was repaired with polymethyl methacrylate (PMMA), Bis-acryl, and flowable composite resin (FCR). The shear bond strength of the bonded specimens was tested using a universal testing machine and the mode of failure was examined with stereomicroscope. Statistical Analysis The Shapiro-Wilk test was used to assess normal distribution, and two-way analysis of variance (ANOVA; alpha = 0.05) was used to find the effect of independent variables on the shear bond strength. The post hoc test was achieved using the Tukey honest significant difference (HSD) test. Results Two-way ANOVA indicated a statistically significant interaction between repair materials and surface treatments in relation to the shear bond strength of 3D-printed resin ( p < 0.001). The three highest shear bond strengths overall were SB repaired with Bis-acryl (17.30 +/- 0.77 MPa), SB + BD repaired with FCR (17.20 +/- 0.29 MPa), and SB + BD repaired with PMMA (16.60 +/- 0.71 MPa), which were significantly higher than their control group ( p < 0.001). However, there were no significant differences between these groups. Notably the lowest shear bond strength in PMMA occurred in the control group (8.49 +/- 0.42 MPa), while the lowest shear bond strength in Bis-acryl and FCR was observed in the SP group (7.28 +/- 0.71 and 8.84 +/- 1.15 MPa, respectively). Conclusion Repair materials and surface treatments play an important role in repairing 3D-printed resin. PMMA and composite resin-based repair materials require both sandblast and a chemical bonding agent, while Bis-acryl-based repair materials only need sandblasting to improve the shear bond strength.