Microleakage of a microhybrid composite resin using three different adhesive placement techniques.

Purpose: To evaluate the efficacy of two adhesive systems in reducing microleakage when applied with three different adhesive placement techniques.

Materials And Methods: Sixty freshly extracted caries-free human premolars and molars were used. MO/DO Class II standardized preparations were performed with the gingival margin placed 1 mm above the CEJ. Teeth were randomly divided into 2 groups (group I: Prime& Bond NT, Dentsply/Caulk; group II: Single Bond, 3M Espe). Each group was divided into 3 subgroups: (A) application of 2 coats and one cure: IA-IIA; (B) 2 coats and 2 cures of each adhesive system: IB-IIB; and (C) one coat of each adhesive along with the manufacturers' B1 flowable resin (0.5-mm thick layer) cured together at once: IC-IIC. Each coat was cured for 20 s at 800 mW/cm2 using a quartz-tungsten halogen light (Elipar Trilight, 3M ESPE). Teeth were then restored using 2-mm increments of an A2 microhybrid composite (Esthet-X, Dentsply/Caulk). All teeth were stored in distilled water at 37 degrees C for 24 h, thermocycled (500x, 5 degrees to 55 degrees C, 30 s dwell) and then placed in a 0.5% methylene blue dye solution for 24 h at 37 degrees C. Samples were sectioned longitudinally and evaluated for microleakage at the gingival margin under a stereomicroscope at 20x magnification. Dye penetration was scored using an ordinal scoring system, where 0: no penetration; 1: enamel penetration; 2: gingival dentin penetration; 3: axial dentin penetration. Kruskal-Wallis and Mann-Whitney tests were used.

Results: A Mann-Whitney U-Test revealed no statistically significant difference between subgroups. Although not statistically significant, P&B NT (two coats and one cure) revealed the lowest microleakage scores.

Conclusion: In the experimental model adopted for this study, microleakage was not affected either by the adhesive or its placement technique.