Morphological comparative study between a fifth-generation adhesive system and a universal system in total-etch mode applied at the cervical region.

For both direct and indirect restorations at the cervical level, the preparation aims to ensure only enamel bonding, due to its proven performance over time. This study sought to evaluate the adhesion to the cervical tooth structure. The aim of the study was to morpho-structurally compare a two-step adhesive system with a universal system in total-etch mode, starting from the hypothesis of the presence of only enamel as the bonding substrate at the level of cavities prepared to the standard depth of 0.4 mm, located 2 mm coronal to the cementoenamel junction. Each adhesive system was assigned a batch of three tooth samples with standard prepared and filled cavities. From each tooth sample, three sections were cut in bucco-lingual direction at the level of the fillings. The sections were prepared for examination by scanning electron microscopy (SEM), using a specific protocol for demineralization and deproteinization. The fifth generation system presented well-represented enamel micro-retentions. Hiatuses were observed at the level of the dentin hybrid layer, despite the formation of intra-tubular resin plugs. The universal system presented less evident micro-retentions on enamel. The thickness of the adhesive layer of the universal system presented higher values compared to the fifth generation system, for both hard dental tissues. Minimal preparations may present dentin exposure, depending on the location of the cervical termination. Acid etching before applying the universal system increased its performance. In the case of enamel, the fifth generation system shows a more favorable adhesion, due to micro-mechanical retention.