Wet vs. Dry Dentin Bonding: A Systematic Review and Meta-Analysis of Adhesive Performance and Hybrid Layer Integrity

Abstract

Objective: This systematic review and meta-analysis aimed to evaluate the effects of moisture control strategies (including wet-bonding techniques, universal adhesives, and etching type) on dentin bonding performance in restorative dentistry. Methods: A comprehensive literature search was conducted across PubMed, Scopus, and Google Scholar, following PRISMA guidelines. Only in vitro and ex vivo studies comparing wet- and dry-bonding protocols, using human dentin substrates, and reporting microtensile bond strength (μTBS) were included. The data were synthesized using a random-effects meta-analysis and the methodological quality was assessed using the MINORS tool. Certainty of evidence was evaluated using the GRADE framework. Results: Nine studies met the inclusion criteria, eight of which were included in this meta-analysis. The moisture control strategies significantly influenced the bonding outcomes, with ethanol and acetone wet bonding yielding higher μTBS and enhanced hybrid layer morphology. The universal adhesives performed effectively under both moist and dry conditions, although their performance varied by the adhesive composition and solvent system. The meta-analysis revealed a statistically significant advantage for hydrated dentin (SMD = +1.20; 95% CI: 0.52 to 1.86; p < 0.001), with the moist and ethanol-treated substrates outperforming the dry and over-wet surfaces. The long-term durability was better preserved with ethanol and acetone pretreatments and the adjunctive use of chlorhexidine. Conclusions: Moisture conditions influence dentin bond strength, but modern universal adhesives show consistent bonding performance across different moisture conditions. Solvent-wet-bonding protocols, particularly with ethanol or acetone, enhance the immediate and long-term performance. While the current evidence is limited by the in vitro designs and heterogeneity, the findings demonstrate protocol flexibility and highlight strategies to optimize adhesion in clinical practice. Future clinical trials are necessary to validate these approaches under real-world conditions.