The Effect of Cementation Load, Unload Time, and Storage Time on Film Thickness and Microtensile Bond Strength Durability of Dual-Cure Resin Cements: An In Vitro Study

This article aims to evaluate the effect of load weight, unload time, and storage duration on microtensile bond strength (µTBS) of dual-cure resin cement to CAD/CAM composite. Forty-eight composite blocks (Grandio Blocs, n = 24 shade A1, and n = 24 shade A4) were randomly assigned to eight groups (n = 3 shade A1, and n = 3 shade A4) based on load weight (1, 3, 5, and 15 kg), and unload time (immediately before light curing or 10 minutes during/after light curing). Bonded blocks (n = 3/group) were sectioned into multiple sticks. Half of the sticks (n = 21) were tested after 24 hours, while the remaining 21 were stored in distilled water at 37°C and tested after 6 months. Sticks for film thickness were evaluated using a stereomicroscope (60 × ). However, the sticks for µTBS were pulled in tension at a 0.5-mm/min crosshead speed. Data were analyzed using ANOVA and the Games–Howell post hoc test (α = 0.05). There was no correlation between µTBS and FT (r = 0.035; p = 0.737). For the FT, only “unload time” had a significant effect (p < 0.001). For µTBS, “load weight,” and “unload time” had no significant impact (p = 0.948 and p = 0.948, respectively). However, “storage time” significantly influenced the results (p < 0.001). Adhesive mode was significantly predominant (56.85%). Unload time is a crucial factor controlling the film thickness of the dual-cure resin cement. However, it does not affect the resin cement µTBS to CAD/CAM composite. Excessive seating load should be avoided when positioning CAD/CAM composite restorations, while a controlled short time may assist in preventing restoration rebound.