Effect of the Ferrule on Fracture Resistance of Teeth Restored with Prefabricted Posts and Composite Cores

Background: The ferrule effect in root treated teeth requiring cast posts and cores has been shown to greatly improve fracture resistance. Studies have also shown that in the case of a cast post and core, the longer the ferrule, the greater the fracture resistance. However few studies have considered the effect of different ferrule designs on prefabricated post and composite core systems.
Aim: This study investigated the effect of different ferrule designs on the fracture resistance of teeth incorporating prefabricated posts and composite cores. It also assessed the necessity of a post in the restoration of endodontically treated teeth.
Methodology: Sixty-two extracted maxillary incisors (centrals and laterals) and canines were randomly assigned into three groups and restored. Two groups had a prefabricated post and composite core with varying ferrule designs. A third group had a core with composite packed into the root canal but no post. An Instron universal testing machine was used to apply compressive loads until failure occurred.
Results: There was no significant difference amongst the three groups as regards fracture resistance. The two groups with prefabricated posts and composite core required a mean force of 931N, std–283 and 931N, Std –242 to fracture. The third with no post group required a mean force of 1036N, std –269 to fracture.
Conclusion: In the restoration of an anterior endodontically treated tooth with a prefabricated post and composite core and where there is at least 2 mm or more of remaining coronal dentine, a ferrule may not be necessary.

Keywords
Endodontically treated teeth, Fracture resistance, Preformed Post, Composite core, Ferrule design, Ferrule effect, Ferrule length, Shoulder, Bevel, Contra-bevel.