Bond strength of orthodontic direct-bonding cement-plastic bracket systems in vitro.

Tensile bond strength and failure location were used to evaluate in vitro the effectiveness of commercial bracket primers for bonding diacrylate cements to plastic brackets. Also, the bond strengths of three two-paste, diacrylate cements were compared with those of three one-step diacrylate cements and an acrylic cement for bonding to three commercial plastic brackets. Bond strength of three diacrylate cements to three plastic brackets ranged from 0.03 to 0.34 kg/mm2 without bracket primer and from 0.51 to 0.85 kg/mm2 with bracket primer. Most failures (83%) occurred within the bracket when the primers were used. For the seven cements tested, bond strengths were highly dependent on the bracket. Bracket T had the highest values of bond strength, followed by bracket L and then R. For brackets L and T, values of bond strength for the one-step cements were equal to or slightly greater than values for the two-paste cements and the acrylic cement.