Enamel acid-etching times on the bond strength of adhesive systems to primary teeth: A systematic review

The aim of this study was to review and analyze the evidence on the enamel acid etching time when bonding to primary teeth. The research question was: Does the acid-etching time affect the bond strength to primary enamel? A systematic search across PubMed, Web of Science, Scopus and Google Scholar databases was conducted up to April 2024 to select studies that compared acid etching times on the bond strength values of adhesive systems to the primary tooth enamel. Studies evaluating other materials than adhesive systems, absence of bond strength values as mean and standard deviation, or ineligible comparison between intervention and control were excluded. Two reviewers screened studies for eligibility and assessed risk of bias. Bond strength data was the primary outcome. From 411 screened studies, 7 reports were assessed for eligibility, and 5 studies were included in the systematic review. Four studies had a high risk of bias and one study had a moderate risk of bias. Acid etching times range from 5 to 60 s. Three studies considered 15 s as a shorter acid etching time and the time of 30 or 60 s as a control. Two studies evaluated the effect of acid etching times on bond strength by comparing the 5, 20, 30, and 60 s groups. Only one study found statistically significant differences between the acid etching times. The main limitation of the study was the inclusion of only 5 studies with a high or moderate risk of bias. Longer acid etching times do not appear to improve the enamel bond strength in primary teeth. This is the first comprehensive review of enamel acid etching time on bonding to primary teeth. It may support the similar acid etching time for primary and permanent tooth enamel.