The impact of extra hydrophobic resin applied over one-step universal adhesives on dentin bonding: A systematic review and meta-analysis

Abstract

This review assessed the effects of extra hydrophobic resin (EHR) application on the bond strength of universal adhesives (UAs) to sound dentin. A systematic search was performed by two independent researchers in Web of Science, SciELO, Cochrane Library, Scopus, and PubMed until February 2025. The eligibility criteria included in vitro studies that evaluated the immediate or aged bond strengths of one-step UAs to sound dentin with EHR in self-etch mode or etch-and-rinse mode. Clearfil SE Bond was considered as the positive control group. Meta-analyses were conducted using a random-effects model in the RevMan Manager program (p < 0.05). Confidence intervals were calculated using the Hartung-Knapp-Sidik-Jonkman method. Of the 22 relevant studies assessed in full-text, 9 were included in the meta-analysis. EHR application significantly increased the immediate or aged bond strength of UAs in both etching modes (p < 0.05), except for the immediate bond strength in the etch-and-rinse mode. The bond strength of UAs was reduced considerably by ageing, regardless of the application mode (p < 0.05). The EHR application improved the bonding durability of UAs, except for ultra-mild/mild universal adhesives in self-etch mode. UAs with EHR in the self-etch mode presented considerably lower performance than the positive control group, regardless of testing time. In the etch-and-rinse mode, those with EHR showed similar performance to the positive control group.