Comparative Analysis of Enamel Conditioning Methods on Shear Bond Strength of Orthodontic Brackets: An In-Vitro Study

Background Conventional enamel conditioning with 37% phosphoric acid is commonly used for orthodontic bracket bonding but causes enamel demineralization. Erbium, chromium-doped yttrium scandium gallium garnet laser conditioning has been proposed as an alternative. This study compared the shear bond strength and adhesive remnant patterns of orthodontic brackets following three enamel-conditioning protocols. Methods Fifty-one extracted human premolars were randomly allocated to three groups (n = 17 per group). Enamel was conditioned with 37% phosphoric acid for 15 seconds in Group I, an erbium, chromium-doped yttrium scandium gallium garnet laser (2780 nm, 2 W, 25 Hz) for 10 seconds in Group II, or acid etching followed by laser irradiation in Group III. Stainless steel orthodontic brackets were bonded, and shear bond strength was measured using a universal testing machine. Adhesive remnants were assessed using the Adhesive Remnant Index and digital image analysis. Statistical significance was set at p < 0.05. Results Median shear bond strength was 13.70 MPa in the acid group, 11.55 MPa in the laser group, and 16.24 MPa in the combined group. No statistically significant difference was found among the groups (χ 2 [2] = 4.17, p = 0.229). Adhesive Remnant Index distributions differed significantly among the groups (χ 2 [6] = 18.17, p = 0.0008). Score 3, indicating that all adhesive remained on the enamel, was most frequent in the acid group. Score 0, indicating that no adhesive remained, was most frequent in the combined group. Conclusions All three conditioning protocols produced clinically acceptable shear bond strength. Combined acid and laser conditioning produced the highest median bond strength and less residual adhesive after debonding, although the difference in bond strength was not statistically significant.