Evaluation of the fracture resistance of remaining thin-walled roots restored with different post systems

Abstract

The purpose of this work was evaluating the fracture strength of bovine roots weakened experimentally, restored with two different techniques: internal reinforcement of root canal walls with composite resin and a cast metal post and core or anatomic post (glass fiber post associated with composite resin). Thirty bovine lower central incisive were selected and transversally sectioned, remaining 14 mm of root in order to approximate to the human maxillary central incisive.  A sequence of standardized wear was used to weak the root until the walls remaining achieved from 0.5 to 0.7 mm of thickness at the cervical edge. Two groups were separated randomly (n=15) in order to test the roots reinforced with composite resin associated with cast metal post and core (CMP), or roots restored with composite resin associated to the glass fiber post (GFP). The test were applied in a Universal Test Machine (EMIC) with tangential compressive loading focused on the lingual face of core in an angle of 135° with the long axis of the tooth at a crosshead speed of 0.5 mm/min until failure occurred. The results showed that the fracture strength of remaining roots with weakened walls was influenced by the restorative technique, and the higher values of strength fractures were observed in the group of roots reinforced by composite resin associated with CMP (p<0.001) when compared to the group of roots restored with anatomic post.