Effect of Displacement of Bracket Position after Initial Placement on Shear Bond Strength: An In vitro Study

Displacement of bracket after initial placement on tooth surface in the precure phase of bonding influences the shear bond strength.

The aim of this study was to evaluate the influence of bracket displacement during the precure phase after initial placement on the tooth surface on shear bond strength of chemical cure and light cure composites.

In vitro experimental study.

Stainless steel orthodontic premolar brackets were bonded to the buccal surfaces of 88 maxillary 1^st premolar teeth. Teeth were divided into four groups: (1) Group 1 - Control group for light-cure composites, (2) Group 2 - Displacement group for light-cure composites, (3) Group 3 - Control group for chemical cure composites, and (4) Group 4 -Displacement group for chemical cure composites. In the control groups, the brackets were bonded with no precure bracket displacement. In the displacement groups, the brackets were bonded with 2 mm precure linear displacement. Photoactivation was carried out for light-cure composites. Shear bond strength tests were carried out using the universal testing machine. Statistical analysis used: Data were analyzed using the one-way analysis of variance test.

The mean shear bond strength of Groups 1, 2, 3, and 4 were observed to be 14.49 ± 0.75, 13.40 ± 0.61, 12.34 ± 0.53, and 11.55 ± 2.43MPa, respectively, with the displacement groups showing lower shear bond strength when compared to the control groups. Whether displaced or not, chemically cured composites showed lower bond strength when compared to light-cured composites.

Displacement of brackets during bracket placement seemed to reduce the enamel bond strength after the final positioning of the bracket.