Shear Bond Strength of Metallic Brackets: An In Vitro Study

Objective: To evaluate in vitro the shear bond strength of metallic brackets. Material and Methods: Forty premolars were divided into four groups (n = 10) according to the type of brackets used (G1: Morelli (R) Light; G2: Morelli (R) Standard; G3: Morelli (R) Max; G4: Abzil (R) Agile). For bonding, Transbond XT (R) (3M Unitek) resin was used in all groups. Teeth were embedded in 3/4 inch PVC tubes with special plaster stone, perpendicular to the ground. Brackets were fixed on the geometric centers of the exposed crowns. After bonding, teeth were stored in distilled water, incubated at 37 degrees C for 24 hours and submitted to 500 thermal cycles for 30 seconds in each bath (5 degrees C and 55 degrees C), respectively. The bond strength test was performed on the Instron (R) mechanical testing machine with 3kg load cell at speed of 0.5mm/min. Data were submitted to statistical analysis through the Statistica (R) software, version 5.0, by Kruscal Wallis test, ANOVA and Tukey (p< 0.05). Results: There was no statistically significant difference in the ARI scores; whereas for shear resistance, this difference was significant (Averages: G1 - Light: 17.53MPa; G2 - Standard: 18.11MPa; G3 - Max: 29.33MPa; G4 - Agile: 11.37MPa) and G3 showed better performance, compared to the others. All other groups showed similar behavior among themselves. Conclusion: Max bracket had the highest shear strength. Further studies should be conducted to investigate the meshes of brackets tested in this study.