Fracture resistance of structurally compromised root filled bovine teeth restored with accessory glass fibre posts

Aim To evaluate the mechanical behaviour of structurally compromised root filled bovine roots after restoration with accessory glass fibre posts. Methodology Fifty roots of bovine teeth received conventional post preparations with a cervical diameter of 3.5 mm. The roots were assigned to five groups (n = 10): group MP-cast metal post, group GP-glass fibre post and group AGP-glass fibre post plus accessory glass fibre posts. In groups GP-R and AGP-R (similar to groups GP and AGP), 2 mm of coronal tooth structure were left intact. All groups were subjected to an elastic limit assay and tested in an universal machine for fracture resistance. Repeated measures ANOVA were performed to examine differences in fracture resistance; fracture modes were analysed by Fischer's exact test. Results The mean fracture resistance values (kgf) were 61.8 ( MP), 63.1 ( GP), 55.5 ( AGP), 56 (GP-R) and (53.1) AGP-R. No statistically significant difference was found between groups. The Fisher's exact test indicated significant differences ( P < 0.05) in the fracture mode amongst groups MP, GP and AGP, indicating 100%, 50% and 10% of catastrophic fractures, respectivelly. Conclusions The use of accessory glass fibre posts affected the fracture mode favorably: 90% of fractures in group AGP were in the coronal third.