Internal and External Ferrule Effect on Anterior Endodontically Treated Teeth

Methods: A total of 72 extracted caries free maxillary central incisors were sectioned 2mm above the cemento-enamel junction and endodontically treated. The teeth were prepared with dentin shoulder for internal/external ferrule and divided into following groups: A,C,E, (0/0mm), B,D,F (0/2mm), G (2/0mm) and H (2/2mm). The specimens were restored using Y-TZP posts with e.max core/crown (A,B), composite core/e.max crown (E,F,G,H) and cast metal post-core/crown (C,D). The specimens (n=12/gr) were embedded in acrylic resin blocks, stored (37°C,24h), loaded until fracture (1mm/min) at angle of 45° and statistically analyzed (ANOVA, Tukey test, p<0.05). Failure patterns were analyzed using optical microscope.

Results: For groups A to H, the results (N) were as follows: 519.4±71.6, 664.6±49.1, 595.3±174.4, 701.9±217.7, 478.1±84.5, 638.6±164.6, 712.5±174.1, and 772.5±134.9. Significantly lower failure loads were measured for the groups with 0/0mm ferrule, compared to those with 0/2mm, 2/0mm and 2/2mm ferrule. Failure patterns within the groups A,B,E,F,G,H reveled catastrophic failure in 29,15,33,17,25,42% and 100% for groups C,D.

Conclusion: Within the limitations of this in vitro study, it can be concluded that the ferrule design increases the fracture resistance of endodonically treated central maxillary incisors. The teeth prepared with internal and external ferrule show highest value of fracture resistance. Therefore, it can be concluded that internal ferrule additionally increases the fracture resistance.