Effect of Averrhoa bilimbi L. extract gel as a natural enamel etching agent on the tensile bond strength of composite resin: an in vitro study

Abstract

Introduction: Composite resin is a restorative material that bonds to tooth structure through micromechanical interlocking. Etching removes the smear layer and creates microporosities, enhancing mechanical retention. Although 37% phosphoric acid is the gold standard, it may cause inflammatory cell infiltration. Averrhoa bilimbi L. contains citric, oxalic, and lactic acids, which may serve as a natural alternative etching agent for enamel. This study aimed to analyze the effect of Averrhoa bilimbi L. extract gel as a natural enamel etching agent on the tensile bond strength of composite resin restorations. Methods: This was an in vitro laboratory true experimental study that employed a post-test-only control group design. Twenty-eight extracted human premolars were divided into four groups (n = 7): three experimental groups etched with 2.5%, 5%, and 7.5% Averrhoa bilimbi L. extract gel, and one control group etched with 37% phosphoric acid. After etching, bonding agent and microhybrid composite resin were applied. Tensile bond strength was tested using a Universal Testing Machine, and data were analyzed using the Shapiro–Wilk, Levene’s, and Kruskal–Wallis tests. Results: The highest mean tensile bond strength was observed in the 37% phosphoric acid group (7.56 ± 3.87 MPa), followed by 7.5% (6.71 ± 1.71 MPa), 5% (6.17 ± 1.39 MPa), and 2.5% (6.04 ± 3.01 MPa) Averrhoa bilimbi L. extract groups. The Kruskal-Wallis test showed p=0.874, indicating no statistically significant difference between the groups. Conclusion: Averrhoa bilimbi L. extract gel demonstrated a tensile bond strength comparable to that of 37% phosphoric acid. The extract gel demonstrated promising potential as a natural etching agent; however, further laboratory and clinical studies are required before it can be recommended for clinical application.