Effect of Thermal Cycling on the Marginal Fit of Provisional Restorations Fabricated Using Three Different Materials: An In Vitro Study

Abstract

Aim and objective: This study aimed to evaluate and compare the marginal fit of different provisional restorations before and after thermal cycling. Materials and methods: The study consisted of three main groups of provisional materials, i.e., bisphenol A-glycidyl methacrylate (Bis-GMA) resin (Protemp II), polymethylmethacrylate (PMMA) self-cure tooth-colored resin, and computer-aided design/computer-aided manufacturing (CAD/CAM) PMMA resin. The groups were further subdivided into 2 subgroups with each having 10 specimens. A typhodont mandibular right first molar was prepared for a full veneer restoration and was cast in a base metal alloy. Polyvinyl siloxane putty index of the master die was prepared and poured with die stone. The provisional crowns were fabricated on these dies and cemented. Conditioning of the specimens was done by storing them in artificial saliva for 10 days. Thermal cycling of the experimental group was done by immersing the samples in two temperature-controlled water baths; 5°C (cold bath) and 55°C (hot bath). The samples were tested by stereomicroscope to find the marginal discrepancies. Paired t-test was done to evaluate the change between baseline to follow-up. Intergroup comparison was analyzed using one-way ANOVA followed by post hoc Tukey's test to compare the mean of measurements. Results: The mean marginal discrepancies were Protemp II (21.8750 ± 3.30 μm), CAD/CAM resin (16.6500 ± 8.14 μm), and self-cure tooth-colored resin (24.2250 ± 3.26 μm) for the provisional crowns. A significant difference was seen in the mean marginal discrepancy of crowns fabricated with Protemp II, CAD-CAM resin, and self-cure tooth molding powder (p = 0.013). Conclusion: The types of materials and the thermal cycling process had a significant effect on the marginal gap of interim restorations. The Bis-GMA resin and CAD/CAM PMMA resin exhibited better marginal adaptability than the PMMA self-cure tooth-colored resin groups, both before and after thermal cycling.