In vitro microleakage of class V restorations in human premolars prepared by Bur or Er, cr: YSGG laser using self-adhering flowable composites versus a flowable composite with self-etch adhesive.

Purpose This in vitro study evaluated the microleakage of four self-adhering flowable composites (SAFCs) and one flowable composite with a self-etch adhesive (S3MF, included as a comparative control group) in Class V cavities prepared by bur or Er, Cr: YSGG laser on human premolars. Materials and methods Fifty premolars were divided into five groups (n = 10). Buccal cavities were prepared with a diamond bur and palatinal cavities with an Er, Cr: YSGG laser. Restorations were placed according to manufacturers' instructions. After 2000 thermocycles, specimens were immersed in AgNO₃, and microleakage was evaluated using a 0-3 ordinal scale under a stereomicroscope and SEM. Data were analyzed with non-parametric tests (α = 0.05). Effect sizes (Cohen's d, η²) together with their 95% confidence intervals (CI) were calculated to indicate clinical relevance. Results Although all groups showed clinically acceptable microleakage scores (≤ 1), VF exhibited the lowest (0.1), while S3MF showed the highest (0.65). Differences were significant between S3MF and VF (p = 0.011), FLD (p = 0.017), and NCS (p = 0.017). Bur-prepared cavities demonstrated less microleakage than laser-prepared cavities (p < 0.001), and microleakage at occlusal margins showed lower scores than gingival margins (p < 0.001). Conclusions Within the limitations of this study, the sealing ability of SAFCs were better in bur-prepared restorations, presumably due to the presence of the smear layer. However, at enamel margins of laser-prepared cavities, microleakage scores were comparable with bur preparations. It can be concluded that both the preparation method and the surrounding tooth tissue should be carefully considered when deciding to use SAFCs to ensure optimal bonding. Further studies are needed to confirm these findings.