The clinical performance of dental resin composite repeatedly preheated: A randomized controlled clinical trial

Objectives: To assess the clinical performance of class II restorations performed by repeatedly preheated resin composite "RC" at 68 degrees C up to ten times. Methods: 105 patients were selected and randomized into three groups, each comprising 35 patients. Each patient was provided with a single class II Bulk-fill resin composite "BF-RC" posterior restoration based on the number of preheating cycles; group I (H0): The BF-RC was packed non-heated, group II (H1): BF-RC preheated once, and group III(H10): BF-RC preheated ten cycles. These restorations were evaluated at 1, 3,6, and 12 months, using the modified United States Public Health Service "USPHS". Statistical analysis was performed using KruskalWallis test, Mann Whitney U test, and Friedmann test, where p = 0.05. Results: All the 105 restorations did not suffer from any clinical situation that recommended replacement regarding retention, fracture, secondary caries, or anatomical form. Although all performed restorations did have Alpha and Bravo scores with good clinical performance, the non-preheated RC restorations"" suffered from relatively inferior clinical performance through the follow-up period regarding marginal adaptation, marginal discoloration, and color matching when compared to preheated groups. One and ten times of preheating conducted better clinical performance. Conclusions: After 12-months follow-up, although no restoration needed replacement or repair in the 3 tested groups, restorations with single and ten times of preheating aided in better clinical performance of RC restorations compared to the non-preheated restorations. Preheating of RC for 10 times could be used safely with good clinical performance of restorations. Clinical Significance: By continually preheating RC syringe up to ten times, the dentist will not only benefit from the enhanced clinical performance and easiness of application but also will use preheated RC syringes without hesitation, relying on the absence of drawbacks related to multiple preheating cycles.