Efeito do bisel e do material restaurador sobre a resistência à fratura coronária em pré-molares inferiores com restaura es cervicais

The aim of this study was to evaluate the fracture strength of lower premolars with cervical restorations, with and without marginal bevel. It was made 64 extracted teeth, that had received cervical standardized preparing, divided in the following groups: Group 1 - sound teeth; Group 2 - teeth only prepared (no restoration); Group 3 - restored teeth with microfi lled composite resin (A110, 3M Espe); Group 4 - prepared teeth with marginal bevel and restored with microfi lledcomposite resin (A110); Group 5 - restored teeth with microhybrid composite resin (Z250, 3M Espe); Group 6 - prepared teeth with marginal bevel and restored with microhybrid composite resin (Z250); Group 7 -restored teeth with low viscosity composite resin (FLOW, 3M Espe); Group 8 - prepared teeth with marginal bevel and restored with low viscosity composite resin (FLOW). For accomplishment of the resistance test, the specimens had been placed individually in a metallic matrix, where the tooth was in a 45° angle in relation to the ground, being exerted a compressive force on the premolar crown in a 0,5 mm/min cross-speed. Data were statistically analysed by ANOVA test (a=0,05) and TUKEY, which had shown that the groups 3 and 4 (A110 without and with bevel, respectively) didn′t show any statistically signifi cant difference in relation to group 1 (sound teeth). Group 2 (prepared teeth) statistically showed signifi cant reduction in the fracture strength in relation to group 1 (sound teeth). The other groups 5, 6, 7 and 8 (Z250 and FLOW, without and with bevel, (respectively) had statistically presented signifi cant differences in relation to group 1 (sound teeth) and had not differed among themselves. Then, it was conclude that the microfi lled composite resin A110 was the only restorative material capable to return the fracture strength lost with the cervical preparation, becoming it similar to sound teeth, and the use of the bevel for cervical restorations did not show benefi ts in relation to the fracture strength.