Impact of Phosphoric Acid Etching Duration on the Bonding Performance of Universal Adhesives on Enamel: A Systematic Review of Laboratory Studies

Objective The optimal duration of phosphoric acid etching (PAE) for enamel bonding remains uncertain, particularly in the context of universal adhesives. The aim of this systematic review was to determine whether shortened etching times (< 15 s) provide comparable bond strength to conventional protocols. Materials and Methods Searches were conducted across four databases, including Embase, OpenGrey through DANS, PubMed, and Scopus. Laboratory studies on human or bovine enamel specimens, treated with varying PAE durations prior to the application of universal adhesives, were included. Data regarding etching protocols, adhesive types, substrate preparation (ground vs. unground enamel), and bond strength outcomes were analyzed. Risk of bias was evaluated using the RoBDEMAT tool. Results Of 762 records screened, eight laboratory studies met inclusion criteria. Etching times of 3–15 s achieved bond strengths that were statistically non‐inferior to conventional durations, with no added benefit from prolonged etching. Ground enamel consistently showed enhanced bond strength with PAE, whereas unground enamel exhibited similar bonding trends. The risk of bias was most often due to inadequate sample size justification, deficiencies in randomization, and absence of blinding. Conclusions Short‐duration PAE (3–15 s) appears sufficient for effective bonding of universal adhesives to enamel, while minimizing potential risk of over‐etching of adjacent dentin. Future research should focus on tailoring etching protocols based on cavity‐specific characteristics and exploring alternative pretreatment methods to enhance bonding performance. Clinical Significance This review suggests that abbreviated phosphoric acid etching (3–15 s) provides enamel bond strengths equivalent to conventional durations when universal adhesives are used. This approach may reduce the risk of inadvertent dentin over‐etching in mixed‐substrate cavities while maintaining optimal adhesive performance.