Residual dentin thickness at the apical third of mandibular first molar mesial root instrumented by nickel-titanium rotary and manual files with different tapers

Aim: The residual root dentin thickness (RDT) in endodontically treated teeth is a major factor affecting their longevity. This study aimed to assess and compare the RDT in teeth instrumented with hand files and also with Dia-PT, Edge Taper Platinum (ETP), and Mani-Silk rotary instruments with different tapers.

Materials and Methods: Sixty-eight extracted human mandibular first molars with separate mesial and distal roots were evaluated. The teeth were mounted in Speedex putty and underwent cone-beam computed tomography (CBCT). The primary thickness of the mesial and distal root canal walls was measured at 1, 2, and 3 mm from the apex. The teeth were divided into four groups (n=17) for instrumentation of the mesiobuccal canal with Dia-PT with 0.09 taper, ETP with 0.08 taper, Mani-Silk with 0.04 taper, and stainless steel K files with 0.02 taper. They were then placed back in the putty in their previous position and underwent CBCT again. The RDT was measured at 1, 2, and 3 mm from the apex in the mesial and distal surfaces, and compared with the baseline values. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests using SPSS version 20 at P<0.05 level of significance.

Results: In the mesial surface, hand files yielded the maximum RDT. Mani-Silk and Dia-PT showed comparable RDT at all levels from the apex lower than the values yielded by hand files, except at 3 mm from the apex, where Mani-Silk yielded RDT comparable to hand files. In the distal surface, hand files and Mani-Silk yielded maximum RDT at all levels from the apex, except at 1 mm, where Mani-Silk showed significantly lower RDT. RDT in ETP and Dia-PT groups was almost similar, and significantly lower than other groups at all levels, except at 1 mm where RDT in ETP group was similar to that in Mani-Silk and hand file groups.

Conclusions: Use of hand files resulted in maximum RDT at all three levels from the apex. Files with greater taper removed greater amount of dentin from the distal surface.