Improved marginal adaptation of composite restorations by using different placement and light polymerization techniques.

Purpose: To verify the influence of placement and polymerization technique on the gap width between dentin and composite restoration.

Methods: Standardized cylindrical cavities (3 mm in diameter, 2 mm deep) with all margins in dentin were prepared on buccal and oral surfaces of 30 extracted human third molars. With regard to the different resin composite filling techniques used, the samples were randomly divided into three groups (n=20): bulk; incremental; pin. Each group was further subdivided into subgroups based on different light polymerization techniques): continuous (40 seconds); discontinuous (2 seconds of activation, followed by 10 seconds of dark interval, then light polymerization continued for 38 seconds). After finishing procedures, impressions were made using polyvinylsiloxane, and epoxy resin replicas were obtained and prepared for scanning electron microscopy. The percentage of the marginal gaps in relation to the whole margin was recorded and statistically analyzed (P)≤ 0.05).

Results: Marginal adaptation of composite restorations placed into the dentin cavities using pin and discontinuously light polymerized presented significantly better results than other two tested groups polymerized in the same manner.

Clinical Significance: The proposed modified incremental placement technique with a transparent glass pin reduces marginal leakage at the interface between composite restoration and dentin; leakage which can jeopardize the longevity of the restoration.