Microleakage in Class II Composite Resin Restorations: Total Bonding and Open Sandwich Technique

The objective of this in vitro study was to evaluate gingival microleakage in Class II total bond resin restorations in comparison to open sandwich technique restorations using different materials. Forty-eight human molar teeth were disinfected and stored in a 0.9% saline solution. In each tooth, two standardized Class II cavities (3 mm x 6 mm x 2 mm) were prepared with the gingival cavosurface margins located 1 mm below the cementoenamel junction. The teeth were divided into 4 equally sized groups (n = 12), and the proximal boxes were treated as follows: in Group 1, no base material was used and the cavity was restored using Syntac Sprint (SS) and Tetric Ceram (TC); in Groups 2, 3, and 4 the gingival portion of the cavity was restored with different base materials (Group 2, Dyract; Group 3, Vitremer; Group 4, Chelon-fil) prior to the placement of the composite resin. After a storage time of 7 days, the restorations were finished and polished. Then, specimens were submitted to thermocycling (500 cycles, 5°C to 55°C, 15 s dwell time) and immersed in a 0.5% methylene blue solution for 24 h. After washing, they were sectioned in a mesio-distal direction. Each restoration was evaluated under a stereomicroscope at 20X by 2 examiners and scored on a 0 to 3 scale according to the marginal leakage. Kappa statistics were used to evaluate the agreement between the examiners. Given the ordinal nature of the scoring system, data were submitted to a nonparametric repeated measures ANOVA. The results were confirmed with a parametric repeated measures ANOVA. Significant differences (p 0.001) among the four groups with respect to dye penetration were detected, with the association Vitremer/Tetric showing the best results. The use of Vitremer in the open sandwich technique presents the lowest degree of microleakage among the treatments considered in this study.