Introduction. Durability of the bond strength between the orthodontic bracket and the enamel is crucial to perform successful treatment with fixed appliance. Contemporary, apart from wide-spread and well-known metallic brackets, ceramic brackets become more popular in orthodontic practice. Aim of the study. The purpose of the current study was to calculate shear bond strength of metal, polycrystalline and monocrystalline orthodontic brackets bonded to bovine enamel with composite resin. Material and methods. Sixty bovine incisors with intact buccal surfaces were used in this study. The teeth were randomly divided into three equal groups. In group 1 stainless steel Victory Series (3M Unitek) brackets were bonded to the enamel. In group 2 polycrystalline Clarity (3M Unitek) brackets were used and in group 3 monocrystalline Radiance (American Orthodontics) brackets were used. Shear bond test was performed 24 hours after polymerization of Grengloo (Ormco) orthodontic adhesive. Results. The highest shear bond strength was found in Victory Series group (mean 10.65 MPa ± 5.2), followed by Clarity group (mean 9.15 MPa ± 1.91) and Radiance group (mean 6.65 MPa ± 1.71). Statistical analysis revealed significantly higher shear bond strength of Victory Series brackets and Clarity brackets in comparison with Radiance brackets. The difference between Victory Series brackets and Clarity brackets was not significant.

Key words: dental bonding, shear strength, orthodontic brackets, composite resins, bovine teeth.