Impact of Self-Etch Adhesives Increased Application Time on Dental Bond Strength: A Systematic Review and Meta-Analysis

In this systematic review and meta-analysis, it was intended to determine whether increasing the application time of self-etch adhesives and universal adhesives could increase the bond strength between composite resin and enamel/dentin. Electronic databases, such as MEDLINE via PubMed, ISI (Web of Science), and Scopus, were thoroughly searched based on the PICOS strategy in order to gather in vitro articles in English with no publication year limit. Studies assessing the bond strength between enamel/dentin and composite resin were selected and further evaluated using self-etch or universal adhesives. Meta-analysis was performed using a random-effect model to determine the difference in the bond value between the specimens that underwent longer adhesive application and the control groups. Amongst 123 gathered studies, 59 were selected for full-text analysis, and 26 were chosen for inclusion in this review. Overall, 14 studies were included in the meta-analysis, and a random-model effect was used for all but one analysis dependent on the heterogeneity percentage. The meta-analysis demonstrated a significant increase in bond strength subsequent to increasing the application time of the aforementioned bonding systems to an extent. Doubling the application time increased the bond strength to both enamel and dentin. However, tripling the application time seemed to be only beneficial to bond strength between enamel and self-etch/universal adhesive systems. The one-component adhesive systems were more impacted by the increased application time than two-component systems. However, not enough data existed on the effect of the pH level of adhesive systems on bond strength value to draw a reach conclusion. Under the limitations of this review, it was concluded that increasing the application time of self-etch and universal adhesives to a certain extent could increase bond strength to both ground dentin and enamel under in vitro conditions.