The influence of the methodological variables on the shear bond strength

Objectives: Evaluate the influence of several methodological variables on the shear bond strength of in vitro studies. Methods: 105 bovine incisors were sectioned at the cervical level. The coronary portion was included in PVC rings, fulfilled with auto polymerized acrylic resin, with its labial surfaces positioned upward. All the samples were prepared for bonding, cleaned and acid etched on the central area of the crowns. In this area, central incisors’ MorelliTM brackets were bonded with ConciseTM (3M/Unitek). Three testing groups were established, according to the studied variable: Group 1—storage previous to bonding (athymol 0.1%; bdistilled water; cfreezing); Group 2—crosshead speed of the universal testing machine (a0.5 mm/min; b1.0 mm/min; c2.00 mm/min) and Group 3—commercial brand of 37% phosphoric acid (a3M/Unitek; bAcid Gel; cAttack Tek). The shear bond strength test was performed at the Emic DL2000TM universal testing machine. Data was analyzed through the Student’s t test for independent samples. Results: In Group 1, the freezing group showed the higher values of shear bond strength when compared to the others, although no statistical difference was observed (p > 0.05). For Group 2, the higher the crosshead speed, the lower the shear bond strength, with no statistical difference. In Group 3, the 3M/Unitek brand showed the highest average of shear bond strength in MPa, but also no statistical difference was shown. Conclusions: The variable analyzed in this research had not presented enough influence to determine significant differences between the results. Abstract