The effect of ferrule on the fracture mode of endodontically treated canines restored with fibre posts and metal-ceramic or all-ceramic crowns.

Objectives: The aim of this study was to evaluate the fracture mode of endodontically treated canines (ETC) restored with glass-fibre posts (GFP) and either metal-ceramic (MC) or all-ceramic (AC) crowns, in the presence or absence of 2 mm ferrule height.

Methods: Fifty recently extracted human maxillary canines were endodontically treated and randomly divided into 5 groups of 10 specimens each. Four groups (with or without ferrule) were restored with GFP, composite cores and either MC or AC crowns. The fifth group with intact ETC served as control. Teeth were loaded to fracture at a 135° angle to their long axis, at a cross-head speed 0.5 mm/min. The fracture modes were divided through optical microscopy to repairable and irreparable. Statistical analysis was performed by means of the Fisher's Exact test.

Results: All groups presented brittle fracture following bending deformation. Irreparable root fractures were the primary fracture mode independently of ferrule. The percentages (%) of repairable fractures were not statistically significant different amongst the MC and AC restored teeth independently of ferrule. However the 2 mm ferrule was associated to a higher percentage of repairable fractures, especially in teeth restored with AC crowns.

Conclusions: The percentage (%) of repairable fractures was higher in all-ceramic compared to metal-ceramic ETC and in restorations with ferrule, although the differences were not statistically significant.

Clinical Significance: This in vitro study supports evidence that neither the type of crown restoration nor the presence of ferrule affects statistically significantly the mode of fracture of ETC restored with GFP.