Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 23 0 2026 04 27 4407 4407 Farzaneh Shirani Dental Materials Research Center, Department of Operative Dentistry, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran Niloufar Jafari Department of Restorative Dentistry, School of Dentistry, Rafsanjan University of Medical Sciences, Rafsanjan, Iran Zahra Alipouriani Department of Pediatric Dentistry, School of Dentistry, Lorestan University of Medical Sciences, Khorramabad, Iran Maryam Adhami School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran 2022 02 25 2024 12 22 Objectives: This study assessed the impact of rinsing water temperature on microleakage of dental composite restorations. Materials and Methods: This in vitro study was conducted on 72 extracted premolars. Buccal and lingual Class V cavities were prepared with gingival margins 1mm beneath the cementoenamel junction (CEJ) and occlusal margins 2mm above the CEJ. The specimens were classified into three groups (n=24) for rinsing with water at 23°C, 4°C, and 45°C before the bonding procedure. Lingual cavities were bonded with a self-etch adhesive, and buccal cavities were bonded with a total-etch adhesive. After composite restoration, the specimens underwent 1000 thermal cycles between 5-55°C. They were then divided into two groups for storage for either 24 hours or 2 months. Optical and electron microscopic assessments were performed to score microleakage at the occlusal and gingival margins of the specimens. The Kruskal-Wallis, Mann-Whitney, and Wilcoxon tests were run to analyze the data (alpha=0.05). Results: Regardless of the bonding system and storage time, microleakage was significantly higher in the 4°C rinsing water group (P<0.05). Gingival margins bonded with the total-etch adhesive had a significantly higher microleakage than the occlusal margins in both 23°C and 45°C groups (P<0.05), but the self-etch adhesive showed no significant difference (P>0.05). Conclusion: According to the results of this in vitro study, rinsing the cavity with warm water (23°C and 45°C) appears to be an effective method to reduce the rate of microleakage. https://fid.tums.ac.ir/index.php/fid/article/view/4407 https://fid.tums.ac.ir/index.php/fid/article/download/4407/2206