Influence of ferrule preparation and the length of fiber post on fracture resistance of endodontically treated teeth

Objective: To evaluate the effect of ferrule preparation and the length of fiber post on the fracture resistance of endodontically treated teeth. Methods: Eighty recently extracted human mandibular premolar were endodontically treated and randomly divided into 8 groups with 10 specimens in each group: Group A1: ferrule and no post; Group A2: ferrule and 5mm post; Group A3: ferrule and 7mm post; Group A4: ferrule and 9mm post; Group B1: no ferrule and no post;Group B2: no Ferrule and 5mm post; Group B3: no Ferrule and 7mm post; Group B4: no ferrule and 9mm post. All specimens were restored with composite resin core and PFM crown. Specimens were subjected to fracture resistance testing in a universal testing machine. The data were analyzed with SPSS 13.0 software. Result: Significantly higher fracture resistance was found in the groups with ferrule(P 0.05). The range of fracture resistance in group A from high to low was A4A3A1A2, but there was no significant difference between any two groups(P 0.05). The range in group B was B4B3B2B1, and the pairwise comparison was significant different except between group B1 and B2, group B3 and B4.Conclusion: Avoiding extra-removal of tooth structure can protect endodontically treated teeth against catastrophic failure.However, when any ferrule can be preserved, increasing the length of fiber post may improve the retention and fatigue resistance of the restoration.