Comparison of Shear Bond Strength:New Orthodontic Primer and Conventional Technique

Objectives:compare the shear bond strength of two kinds of commercially available light-cured and self-cured adhesive bonded to enamel with a conventional technique of etching with phosphoric acid, and a self-etching primer adhesive system. Methods: 80 extracted upper premolars were collected and equally divided into four groups of twenty teeth. The metal orthodontic brackets were bonded with two kinds of adhesive under the different tooth surface preparation, with the following in vitro protocols: Group 1 (n= 20): a conventional etching technique and bonded with Unite bonding adhesive; Group 2 (n= 20): a conventional etching technique and bonded with Transbond XT (3M Unitek); Group 3 (n= 20): Preparation of tooth surface with self-etching primer system and bonded with Unite bonding adhesive, Group 4 (n= 20): Preparation of tooth surface with self-etching primer system and bonded with Transbond XT (3M Unitek). All bonded specimens were stored in distilled water at 37 C for 24 hours and thermocycled at 1000 cycles at 4 – 55 C for 24 hours before debonding. An Instron universal testing machine was used to determine the shear bond strength at a crosshead speed of 0.5 mm/min. Results: the mean shear bond strength of group1, 2 and 4 were significantly greater than group 3, but there were no statistical differences (p> 0.05) among group 1, 2 and 4. Conclusions: the mean shear bond strength from Group 1 (Conventional etching technique + Unite), Group 2 (Conventional etching technique + Transbond XT), and Group 4 (Self-etching primer + Transbond XT) is clinically acceptable. However, Group 3 (Self-etching primer + Unite) has much less bond strength which may not be clinically acceptable