Abstract
BACKGROUND: Preheating resin-based composites (RBC) has been shown to enhance their mechanical and bonding properties. Nevertheless, the effect of preheating RBCs on the performance of orthodontic lingual fixed retainers has been scarcely reported. OBJECTIVES: The aim of this in vitro study was to investigate the effect of preheating flowable RBCs and the types of RBC and wire on the load at failure. METHODS: A total of 64 blocks of resin-embedded pairs of lower incisors were divided into four groups according to RBC/wire types (Tetric N-Flow Bulk Fil restorative (TNF) vs. Transbond LR orthodontic (TRL) composites/Bond-A-Braid braided (B) vs. Ortho-Flex-Tech flexible (O) retainer wires). Each group was then subdivided into room temperature at 25°C (RT) and preheated temperature at 50°C (H) subgroups (N = 16, n = 8). After bonding the wires, the test blocks were subjected to load-to-failure testing, and the maximum load was recorded (Lmax). Statistical analysis using 3-way ANOVA with point-biserial correlations was completed (p < 0.05). RESULTS: Temperature significantly increased L(max) (p < 0.001). Mean L(max) of TRL/B was greater than TNF/O but was not statistically significant (p > 0.05). There was no statistically significant interaction between the variables: RBC, wires, and/or temperature (p > 0.05). CONCLUSION: The study shows preheating RBCs improves their load capacity, reducing lingual retainer adhesive debonding. Therefore, preheating flowable RBCs is effective for retention. Future research should explore different preheating temperatures and long-term outcome conditions.