Evaluation of Shear Bond Strength and Surface Morphology (via SEM) of Different Provisional Crowns and Surface Treatments to PMMA

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.