In vitro biological and adhesive properties of universal adhesive systems on sound and caries-affected dentine: 18 months

The present study aims to evaluate antimicrobial activity, cytotoxicity, as well as resin-dentine microtensile bond strength, nanoleakage and degree of conversion of six universal adhesives, on sound and caries-affected dentine after 18 months. The adhesives Prime&Bond Active (PBA), Scotchbond Universal (SBU), Tetric N-Bond Universal (TNU), Ambar Universal (AMU), Clearfil Universal Bond Quick (CUQ) and One Coat 7 Universal (OCU) were used. Antimicrobial activity was evaluated against Streptococcus mutans. For cytotoxicity, methyltetrazolium assay was used, after 24 h exposure of osteoblast-like cells line to the adhesive`s dilution of 1, 0.1, and 0.01 v/v%. After, the adhesives were applied in etch-and-rinse or self-etch strategies on sound or caries-affected dentine surfaces, resin composites restorations were constructed. Then, the specimens were sectioned to obtain sticks to be evaluated in microtensile bond strength and nanoleakage after 24 h and 18 months, and degree of conversion after 24 h. ANOVA and Tukey`s test were applied (α = 0.05). For antimicrobial activity, CUQ showed higher values than all adhesives. For cytotoxicity, the PBA, AMU, CUQ and OCU adhesives presented cytotoxicity in different dilutions. For microtensile bond strength , OCU presented the lowest values, regardless of time, dentine or strategy. For nanoleakage , differences were observed among adhesives depending on time, dentine or strategy. For degree of conversion , TNU presented the highest values, while PBA and OCU presented the lowest values. Worst values of microtensile bond strength and nanoleakage were always obtained in caries-affected dentine after 18 months. Thus, not all universal adhesives behave the same in terms of antimicrobial activity and cytotoxicity. However, the majority showed worst results when applied in caries-affected dentine, mainly after 18 months. Clinical relevance. Universal adhesive systems may have differences in their biological and adhesive properties, both on sound, but mainly in caries-affected dentine after 18 months.