Adhesives Air-Drying and Bond Strength: A Systematic Review and Meta-Analysis

Abstract

Objectives: The objective of this review was to evaluate the effect of air-drying time on the bond strength of adhesives to dentin, in previously published studies and to conduct a meta-analysis to quantify the differences in the bond strength obtained after different air-drying times. Methods: An electronic search was performed using PubMed and Cochrane Library databases. A parallel hand search was performed in non-electronic relevant journals. The included studies were laboratory studies that investigated the effect of adhesive air-drying time on bonding of resin-based adhesives to coronal dentin. Studies which evaluated the bond strength of resin cement or indirect composite restoration were excluded. The methodological quality of included studies was assessed. Meta-analysis was performed using Comprehensive Meta-Analysis software, version 2.0 (Biostat, Englewood, NJ, USA). The results of the meta-analysis were subjected to a further one-way analysis of variance, followed by the Tukey post hoc multiple comparison using R-software, version 3.4.3 (R Foundation for Statistical Computing, Vienna, Austria). Results: Eleven studies fulfilled the inclusion criteria of this review, while only three studies were included in meta-analysis. The effect of adhesive air-drying time on the bond strength was significant in seven studies (64%), material-dependent in three studies (27%), and not significant in one study (9%). Eight studies (73%) presented a medium-risk of bias, and three studies (27%) showed a high-risk of bias. The analysis of micro-tensile bond strength (μTBS) of adhesives showed statistically significant difference between different air-drying times (p ≥ 0.05). The highest mean (μTBS) (37.76±1.5 MPa) was obtained after air-drying of adhesives for 25s, followed by 15s (35.75±2.5 MPa) and 10s (35.10±2.4 MPa) while the lowest mean (μTBS) (27.41±2.3 MPa) was obtained after 5s. Conclusions: Adhesives air-drying time is crucial to the bond strength to coronal dentin. Adhesive air-drying for 5s may be inadequate to obtain high bond strength.