Comparison of universal adhesives used in different etching modes on dentin bond strength: a systematic review and network meta-analysis

BACKGROUND: This study aimed to compare the bond strength of universal adhesives to dentin before and after ageing using a network meta-analysis. METHODOLOGY: A comprehensive literature search was conducted in the Web of Science, Scopus, and PubMed databases. In vitro studies evaluating the bond strength of universal adhesives to sound dentin in self-etch or etch-and-rinse modes, both before and after ageing, were included. Studies were required to include at least one control group (Scotchbond Universal). Data were analyzed using a Bayesian network meta-analysis, and adhesive performance was ranked using SUCRA (Surface Under the Cumulative Ranking) values. Two reviewers independently evaluated the risk of bias in the included studies using the QUIN tool. Reporting/publication bias in the network meta-analysis was further examined with the ROB-MEN tool, and the results were incorporated into the CINeMA framework. RESULTS: Out of 1677 identified studies, 82 met the inclusion criteria for quantitative synthesis. Most studies were assessed as having a low risk of bias (52.4%), followed by a moderate risk (46.4%) and a high risk (1.2%). Twenty-two universal adhesives were included in the network meta-analyses. According to SUCRA rankings, G2-Bond Universal (GC, Japan), OptiBond Universal (Kerr, USA), and Scotchbond Universal (3 M ESPE, USA) showed the highest bonding potential in self-etch mode before ageing. After ageing, G2-Bond Universal, Zipbond Universal (SDI, Australia), and Scotchbond Universal remained the top-performing adhesives in self-etch mode. In the etch-and-rinse mode, Zipbond Universal consistently demonstrated the highest performance both before and after ageing. Overall, most comparisons showed high certainty of evidence. CONCLUSIONS: The bond strength of universal adhesives appears to be determined primarily by their application strategy and material composition, rather than by the presence of specific functional monomers. However, this observation should be interpreted with caution, as further clinical validation is needed to confirm these findings.