چكيده لاتين :
Background & Aim: The purpose of this study was to compare the effect of sandblasting on shear bond strength of three metal brackets.
Methods & Materials: For this experimental study, 180 human maxillary and mandibular first and second premolars teeth obtained from orthodontic patients were cleaned and stored in 0.1% thymol solution. The teeth randomly assigned to either the control (n-90) or experimental (n=90) groups. Each group subdivided into three equal groups (n=30). In control groups, three different non -- sandblasted metal brackets (3M Uniteck, Dentaurum and Am orthod) were bonded with 3M (Unitek) no - mix resin. In the next stage of experiment, similar brackets were sandblasted and used. All samples pumiced and were etched with 37% phosphoric acid (3M unitek) for 15 seconds. The teeth were embedded in blocks of autopolymerization polymethyl methacrylate (2x2x3 cm), using a special device to make their slots parallel to horizontal plane. Samples were stored in distilled water at room temperature for 24 hours before testing. Testings were performed with an instron machine. The data were analyzed by ANOVA, LSD, Kruskal - wallis and Man - whitney tests.
Results: In non-sandblested groups, the results were analysed by ANOVA and LSD non-comparisons tests. In sandblasted groups non-parametric tests including Kruskal wallis and mann - whiteny used for statistical analysis. For evaluating each pair bracket type untreated and sandblasted, Levene and t - test analysis were used. Mean shear bond strength of untreated groups were 15.51, 16.60, and 18.58 Mpa for Am Orthod, Dentaurum, and 3M Unitek companies respectively. Mean shear bond strength of sandblasted groups were 15.18, 19.38, and 18.66 Mpa for Am Orthod, Dentaurum, and 3M Unitek companies respectively. Increase in shear bond strength of Dentaurum brackets was statistically significant, but was not significant for 3M brackets.
Conclusion: Sandblasting usually increase shear bond strength in metal brackets. In specific circumstances that, extra shear bond is needed, bracket sandblasting could be used according to the manufacturer instrumentation, combined with chemical adhesion promoters.
