Influence of glass fiber post adaptation in the root canal on the tensile strength

Abstract

This study investigated the tensile strength of glass fibre posts and the failure pattern occurring according to the degree of adaptation of posts in the root canal. Forty human canines were selected, with a medium of ninety days of extraction. Before and during the experiment, the teeth were storaged in humid enviroment (physiological sodium chloride solution). After the root canal treatment, the crown of these teeth was sectioned for standardization of the root remaining (medium length of 15 mm, mesiodistal diameter of 5 a 5,5 mm and buccolingual diameter of 7 a 7,5 mm). The root were separated in four groups (n = 10): in Group 1, the entire root canal was prepared with a Largo bur No. 4; in Group 2, the root canal was prepared as for Group 1, followed by widening of the cervical third with a diamond bur No. 1016 HL; in Group 3, after initial preparation as for Group 1, the cervical and middle thirds were widened with a diamond bur No. 1016 HL; in Group 4, the entire root canal was widened with a diamond bur No. 1016 HL. The root canals were prepared to a depth of 9mm, and posts Reforpost nº 2® were luted with ScotchBond Multi- Purpose Plus and resin cement RelyX CRA. The coronal portion of the post was constructed with composite resin Filtek Z250. After storage for 24 hours, the specimens were submitted to tensile strength tests in a universal testing machine Kratos model K-2000MP®, at the speed of 0,5mm/min. The following values were found: Group 1 -47.67 kgf (± 12.80); Group 2 - 40.92 kgf (± 9.94); Group 3 - 43.63 kgf (± 9.30); Group 4 - 37.57 kgf (± 8.62). There was no statistically significant difference between groups (p < 0.05). In Groups 1, 2 and 3, the most common failure pattern was adhesive (dentin/cement interface), whereas in Group 4 there were 50% of adhesive failures and 40% of combined failures.