[SEM investigation of composite restoration adaptation to enamel after use of total etch and self etch adhesive system].

Introduction: Quality and durability of enamel/composite interface essentially depend on an adhesive restorative system.

Objective: The aim of this study was to evaluate the quality of marginal adaptation of composite adhesive systems to enamel by scanning electron microscopy (SEM), and to analyse the morphology of the enamel surface along margins of composite restorations, following exposure to cariogenic solution.

Methods: The study material included 56 extracted human third molars. Class V cavities were prepared with margins at enamel. Cavities were restored with Single Bond/Z250 and Single Bond/Filtek flow, using the total etch adhesive system, and Prompt-L-Pop/Z250 and Prompt-L-Pop/Filtek flow, using the self etch adhesive system. After the restorative procedure, the restorations were submitted to demineralization during 7 and 28 days. Samples were stored in a cariogenic solution (lactic acid, pH 4.5; 0.1 M) at 37 degrees C or in deionized water (the control group). The margins of restorations and perimarginal enamel were examined by scanning electron microscope (SEM). The gap formations around restoration were measured on cervical, occlusal and approximate margins.

Results: The usage of the total etch adhesive system showed statistically significant lower marginal gap width around composite restoration, compared with the self etch system (p < 0.01). The SEM examination also showed perimarginal enamel zones presenting several signs of demineralization and erosion (alteration of rods, porosities) after acting of a cariogenic solution, in both adhesive methods. Less alteration was found on the enamel surfaces not included in the perimarginal zone.

Conclusion: Treating the cavity with 35% phosphoric acid in the total etch system significantly improved the adaptation of the composite resins to enamel, compared with the self etch treatment. Stronger demineralization of the perimarginal enamel in a cariogenic solution was observed around all restorations in both adhesive systems.