Comparison of Two Post Preparation Methods in Mandibular Second Molars with a C-shaped Root Canal Configuration.

To compare the reduction of residual dentine thickness of two different post preparation methods on the mandibular second molars with a C-shaped root canal configuration.A total of 26 extracted right mandibular second molars with a C-shaped root canal configuration were selected and paired based on similar canal morphology. Each of the paired teeth was randomly allocated to the heat and ultrasonic instruments group (HU group) or Peeso Reamer (Mani, Utsonomiya, Japan) group (PR group) (n = 13) and received post preparation with different instruments after the same endodontic treatment. The reduction of residual dentine thickness and the minimal remaining dentine thickness at the apical sections at 4 or 7 mm below the cementoenamel junction (CEJ) were recorded. The data were analysed using an independent samples t test (α = 0.05).The reduction of residual dentine thickness for the HU group was less than that for the PR group in the two sections. Moreover, at the section 7 mm below the CEJ, the teeth reduction of the distolingual wall in the HU group (0.022 ± 0.007 mm) was significantly lower than that in the PR group (0.101 ± 0.013 mm) (P < 0.01).Using heat and ultrasonic instruments to perform post preparation could follow the original canal configuration to save more tooth structure in the remaining root canal wall, minimise the reduction of residual dentine thickness and decrease the incidence of root canal perforation.