Effect of root canal preparation,type of endodontic post and mechanical cycling on root fracture strength

Objective: to evaluate the impact of the type of root canal preparation,intraradicular post and mechanical cycling on the fracture strength of roots. material and methods: eighty human single rooted teeth were divided into 8 groups according to the instruments used for root canal preparation (manual or rotary instruments),the type of intraradicular post (fiber posts- frc and cast post and core- cpc) and the use of mechanical cycling (mc) as follows: manual and frc; manual,frc and mc; manual and cpc; manual,cpc and mc; rotary and frc; rotary,frc and mc; rotary and cpc; rotary,cpc and mc. the filling was performed by lateral compactation. all root canals were prepared for a post with a 10 mm length,using the custom #2 bur of the glass fiber post system. for mechanical cycling,the protocol was applied as follows: an angle of incidence of 45°,37°c,88 n,4 hz,2 million pulses. all groups were submitted to fracture strength test in a 45° device with 1 mm/ min cross-head speed until failure occurred. results: the 3-way anova showed that the root canal preparation strategy (p<0.03) and post type (p<0.0001) affected the fracture strength results,while mechanical cycling (p=0.29) did not. conclusion: the root canal preparation strategy only influenced the root fracture strength when restoring with a fiber post and mechanical cycling,so it does not seem to be an important factor in this scenario.