Korean J Orthod.  2025 Jan;55(1):15-25. 10.4041/kjod24.073.

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

• Rodríguez-Chávez JA
• Flores-Ruiz HM
• Flores-Ledesma A
• García-Pérez A
• Bazán-Diaz L

• KMID: 2565025
• DOI: http://doi.org/10.4041/kjod24.073

Abstract

Objective
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.
Methods
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.
Results
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).
Conclusions
This study suggested that the shape of bracket meshes influenced shear bond strength.

Keyword

Bracket; Adhesive; Shear bond strength; Scanning electron microscopy

Figure

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  Figure 1 Mesh images of the different metallic brackets. G1, Alexander; G2, Mini Sprint® Brackets; G3, In-Ovation R CCO; G4, Gemini SL Self-Ligating Brackets; G5, Classic mini 2G Stylus®; and G6, Gemini Metal Brackets. In G4A, a magnification of G4 at 90×, it is observed that a greater detail of the failure in the union of its rods is in the center of the bracket. In G5A, a magnification of G5 at 100×, the failure in the union of the rods can be seen.

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  Figure 2 Mesh images of the different aesthetic brackets. In G7, ClarityTM Advanced, it is possible to see a defect, where G7A, at a higher magnification of 80×, shows it; meanwhile, in G7B, at 160×, the size of the aggregate can be seen. In G8, Crystall-Ize®, it is observed that the aggregates are not homogeneous, and G8A at 160× shows them in detail. Finally, in G9, Ceramic Series Flexx 2G®, the mesh without defects can be observed.

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  Figure 3 Adhesive remnant index by bracket group.

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  Figure 4 Percentage of bracket meshes with or absence of tooth enamel, namely percentage of teeth with or absence of enamel loss, respectively.

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  Figure 5 Mesh images at 25× and 30× of metallic brackets after debonding. G1, Alexander; G2, Mini Sprint® Brackets; G3, In-Ovation R CCO; G4, Gemini SL Self-Ligating Brackets; G5, Classic mini 2G Stylus® and G6, Gemini Metal Brackets. In G3A, a higher magnification (250×) of figure G3 is marked with a circle highlighting a fragment of tooth enamel (enamel loss), where the presence of enamel prisms is visible. In image G5A, a 250× magnification of figure G5 shows the failure in the union of the rods.

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  Figure 6 Mesh images at 25× of aesthetic brackets. G7, ClarityTM Advanced; G8, Crystall-Ize®; and G9, Ceramic Series Flexx 2G®. G7 shows the bracket mesh with the absence of tooth enamel. G8 and G9 show a tooth enamel fragment marked in a yellow circle, and then in G8A and G9A, which are magnifications of G8 and G9 at 250×, the presence of tooth enamel prisms can be observed.

Reference

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