Abstract:

Objective

To evaluate the effect of different ferrule lengths on the fracture resistance of residual roots restored with carbon fiber post-and-core system.

Methods

24 extracted， intact mandibular first premolars were endodontically-treated， and sectioned 1.0 mm coronal to the buccal cementoenamel junction （CEJ） for the preparation of the residual-root model. The simulated forced eruption method was done for the ferrule design in the cervical tooth structure. All the residual root models were randomly divided into three groups according to the ferrule length from 0 mm to 2.0 mm with 1.0 mm interval each （group A， B and C）. After restoration with prefabricated carbon fiber postand-core system， each specimen was embedded in a self-curing acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown， then loaded at 150 degrees from the long axis in a universal testing machine at the crosshead speed of 1.0 mm/min until fracture. Data were recorded and analyzed using ANOVA and Tukey HSD tests， and Fisher's exact test.

Results

Mean failure loads （kN） for A，B， C groups were： 1.13 （S.D. 0.15）， 1.63 （0.14） and 1.92 （0.19）. Significant differences were shown for the effect of ferrule design （F=48.437， P＜0.001）， and among the three groups （P＜0.05）.

Conclusion

The design of an 1.0 to 2.0 mm long ferrule placement on the apical crown margin resulted in a significant increase in fracture resistance of residual roots.

Key words: Forced eruption, Ferrule, Carbon fiber post, Residual root, Fracture resistance