Comparative evaluation of the effect of 37% orthophosphoric acid pre-etching on the microtensile enamel bond strength using universal adhesive and two-step self-etch adhesive systems - An in vitro study.

Abstract

The significance of enamel etching has been well-researched and established. Limited literature is available comparing the enamel bond strengths of the two-step self-etch adhesive system and the newly introduced universal adhesive (UA) system with prior acid etching. The aim of the study was to evaluate and compare the microtensile bond strength (μTBS) of composite to enamel with and without 37% orthophosphoric acid pre-etching using a recently introduced UA and a two-step self-etch adhesive. This in vitro, experimental study was conducted on 48 extracted human third molar teeth. Two enamel surface fragments were obtained per tooth, polished using 600-grit silicon carbide abrasive paper, and randomly divided into four groups-CLEARFIL SE BOND with and without acid pre-etching and G-Premio Bond with and without acid pre-etching. The samples were etched using 37% phosphoric acid gel for 30 s, followed by the bonding protocol. Composite resin blocks were built incrementally to a thickness of approximately 6 mm, and the restored samples were stored in distilled water for 24 h at 37°C. They were then sectioned, mounted, and subjected to a μTBS test using a universal testing machine. Statistical analysis of the data was performed using one-way ANOVA and Tukey's post hoc test using SPSS software version 22.0. Samples bonded with the UA subjected to prior acid etching protocol demonstrated the highest enamel μTBS. In contrast, those treated with the two-step self-etch adhesive without prior acid etching demonstrated the lowest enamel μTBS. Pre-etching with phosphoric acid significantly increased the enamel bond strength of both bonding agents, with the universal agent showing better results than the two-step adhesive system. Enamel etching with phosphoric acid significantly increases the bond strength of self-etch adhesives. UA with prior acid etching showed the maximum enamel μTBS. Two-step self-etch adhesive without prior acid etching yielded enamel μTBSs unacceptable for long-term, durable bonding.