Scanning electron microscopy analysis of metallic and aesthetic bracket meshes before and after debonding

To study the influence of bracket base meshes on shear bond strength and observe them using a scanning electron microscopy (SEM) before and after debonding.

Ninety brackets were divided into nine groups of 10 samples each: G1-Alexander, G2-Mini Sprint^® Brackets, G3-In-Ovation R CCO, G4-Gemini SL Self-Ligating Bracket, G5-Classic mini 2G Stylus^®, G6-Gemini Metal Brackets, G7-Clarity^TM Advanced, G8-Crystall-Ize^®, and G9-Ceramic Series Flexx 2G^®. Groups G1 to G6 and G7 to G9 consisted of metallic and aesthetic brackets, respectively. Initial photographs of all brackets were taken through SEM at 25X magnification. The brackets were then bonded to premolars using Transbond^TM XT, and a shear bond strength test was conducted after 24 hours using an Instron machine at 1 mm/min. After debonding, the bracket meshes were observed using SEM.

Before bonding, 72.22% of brackets didn't present mesh defects, while 27.77% did. SEM analysis revealed that G4 and G5 presented defects in 100%, G7 in 40%, and G8 in 10%. The average shear bond strength of 9.67 ± 2.84 MPa and 11.21 ± 4.99 MPa were obtained for both metallic and aesthetic brackets, respectively. A Pairwise-Wilcoxon test with Benjamini-Hochberg correction was conducted to determine specific statistical differences between the groups, revealing significant differences based on bracket type and shear bond strength (P < 0.009).

This study suggested that the shape of bracket meshes influenced shear bond strength.