Does Preheating Matter? A 36‐Month Randomized Controlled Trial of Non‐Carious Cervical Lesion Restorations Performed With Preheated and Non‐Preheated Composite Resins

OBJECTIVES: This split-mouth randomized equivalence-controlled trial compared the survival rate, based on material fracture and retention, of a preheated thermo-viscous composite resin (PH) and a non-heated composite resin (NH) for non-carious cervical lesions (NCCLs). MATERIALS AND METHODS: Sixty adult participants in good general and oral health, with at least two comparable NCCLs and 20 teeth under occlusion, were eligible for the study. A total of 120 NCCLs were restored, half with VisCalor Bulk, Voco (PH), preheated to 68°C using a bench heater, and half with Admira Fusion, Voco (NH), used at room temperature. A universal adhesive was applied with a selective enamel etching approach before placement of the composite resin. Restorations were evaluated for 36 months according to the FDI World Dental Federation criteria. Survival was analyzed using Kaplan-Meier and equivalence tests, with Hazard ratios (HRs) and 95% confidence intervals (CIs) estimated by Cox models. Secondary FDI outcomes were analyzed using the chi-square test or Fisher's exact test (α = 0.05). RESULTS: After 36 months, the recall rate was 90%. Ten restorations failed, with five losses in the PH group and five in the NH group (p = 0.95). The material fracture and retention rates, with 95% CIs, were equivalent at 90.7% (83.3-98.8) for both the PH and NH groups (p < 0.001). Cox regression analysis showed no significant difference in failure risk between PH and NH (HR = 0.96; 95% CI: 0.28-3.33). No significant difference was observed in the other secondary outcomes, and all remained clinically acceptable. CONCLUSION: Preheating makes no difference, since both composite resins showed high and equivalent survival rates above 90% after 36 months of clinical service. CLINICAL SIGNIFICANCE: Preheating did not provide additional benefits regarding fracture, retention, or other clinical outcomes.