Fracture resistance of bonded fibre posts with different shape and taper: conventional versus conservative approach

Aim: To investigate in vitro the fracture resistance of two different post systems, a conventional one with post space preparation using a drill and an alternative one adapted to the canal shape. Methodology: After sample size calculation, the crowns of 26 single-rooted freshly-extracted teeth were removed with a disc 1 mm coronal to the cemento-enamel junction. The canals were shaped with Mtwo rotary files up to size 40, 0.06 tpaer and filled with the continuous wave of condensation technique leaving the coronal 9 mm of the canal unfilled. After the post space preparation by a dedicated drill, double-tapered fibre posts (DT Light-Post) were cemented in half of the roots (G1, n = 13). 0.06 tapered fibre posts (Tech S Endoshape) were trimmed to fit the canal of the remaining roots (G2, n = 13) and then cemented without post space preparation. A self- adhesive cement (RelyX Unicem) was used in both groups. The posts were cut 5 mm from the root coronal surface. The specimens were embedded in acrylic resin and the top of the post was loaded under continuous compressive force (45°, 0.75 mm/min) to measure the maximum breaking load (N). Data were statistically analyzed by using a Student’s t-test (α = 0.05). Results: The mean maximum breaking loads ±SD were G1 = 164.07 ±21.54 and G2 = 151.22 ±14.69. The difference was not statistically significant (P = 0.093). Only post fractures were detected, with all the roots remaining intact. Conclusions: Within the limitation of the study, conservative posts without post space preparation performed similarly to conventional ones. In order to avoid procedural errors during the post space preparation and to spare tooth structure a conservative approach seems advisable.