EFFECT OF PREPARATION DESIGN ON MECHANICAL PROPERTIES OF ENDODONTICALLY TREATED TEETH

This study is aimed to evaluate the effect of different tapers and restorative cavity designs on the fracture resistance of the endodontic retreated tooth. Sixty lower first premolar human extracted teeth from the teeth bank of faculty of dentistry, Ain Shams University have been used in this study and divided into 3 different groups. Group I: Access cavity class I preparation was made. Group II: Access cavity occluso-mesial cavity (OM) class II preparation was made. Group III: Access cavity mesio-occluso-distal (MOD) class II cavity preparation was made. These main groups were further sub divided into two sub groups, subgroup A: cleaning and shaping was done using Twisted File (TF) #25 taper 0.04, subgroup B: cleaning and shaping was done using Twisted File (TF) #25 taper 0.06. The fracture resistance of all groups had been evaluated & analyzed; results using Two-Way ANOVA showed that the cavity design had a significant effect on the fracture strength. On the other hand, neither the taper nor the interaction of the independent variables (taper and cavity design) had a significant effect on the fracture strength of teeth. It has been concluded that the remaining coronal tooth structure is the corner stone in weakening the tooth structure while the root canal geometry is not a mechanical cause of failure.