Abstract
PURPOSE OF THE STUDY: To compare the shear bond strengths (SBSs) of different provisional crown materials with various surface treatments when relined with autopolymerizing polymethyl methacrylate (PMMA). MATERIALS AND METHODS: Part 1: Seventy-five specimens were divided into five groups: PMAC (autopolymerizing PMMA), PMAM (CAD/CAM system PMMA), PMAD (3D-printed PMMA), PLAI (injectable polylactic acid [PLA]), and PLAD (3D-printed PLA). All specimens were surface-treated by sandblasting followed by 180 s of MMA application, then relined with autopolymerizing PMMA. Part 2: Forty-five PLAD specimens were divided into three groups: PLAD (control), PLAD MC (methylene chloride treatment), and PLAD AT (acetone treatment), then relined with autopolymerizing PMMA. All samples underwent thermocycling before being evaluated for SBS with a universal testing machine (Shimadzu, Japan). Statistical analysis was performed using one-way ANOVA and Tukey's HSD at a significance level of p ≤ 0.05. Failure modes were examined using a stereomicroscope, and surface morphology was evaluated by scanning electron microscopy (SEM). RESULT: In Part 1, the mean SBS values in MPa were: PMAC (26.85 ± 1.31), PMAM (22.92 ± 1.20), PMAD (13.98 ± 1.20), PLAI (10.19 ± 1.59), and PLAD (8.44 ± 1.14). Significant differences were found between all groups (p ≤ 0.05). In Part 2, the mean SBS values in MPa were: PLAD (8.44 ± 1.14), PLAD MC (8.35 ± 0.84), and PLAD AT (7.83 ± 1.13). No significant differences were found between the three groups (p > 0.05). PMAC, PMAM, and PMAD exhibited mixed failure modes in 87.5%, 80%, and 73.3% at the fractured surfaces of the specimens, respectively. In contrast, PLAD and PLAI displayed 100% adhesive failure. PLAD, PLAD MC, and PLAD AT also showed 100% adhesive failure at fractured surfaces. CONCLUSION: The PMAC group achieved the highest SBS among all tested materials. Surface treatment of PLAD with methylene chloride or acetone did not significantly improve SBS compared to the untreated control.