Comparison of canal transportation and centering ability of K-files the ProGlider file and G-file : a micro-computed tomography study of curved canals

Abstract

The aim of this in vitro study was to investigate the canal centering ability and apical root canal transportation of pre-curved stainless steel K-files, the ProGlider file and GFiles after glide path enlargement in curved root canals of extracted human mandibular molars using micro-CT scanning. The working times for the different glide path enlargement methods were also recorded. Ninety untreated curved root canals from extracted molars were randomly divided into three groups (n = 30). Group 1: manual glide path preparation with size 0.10 Kfile and enlargement with size 0.15 and 0.20 hand K-files; Group 2: manual glide path preparation with size 0.10 K-file and enlargement with NiTi rotary G-Files; and Group 3: manual glide path preparation with size 0.10 K-file and enlargement with the NiTi rotary ProGlider file (ISO tip size 16). Micro-computed tomography was used to scan the teeth before and after glide path enlargement. Three-dimensional images were reconstructed from the pre- and post-instrumentation scans to enable a comparison of the centring ability at three selected levels: 1 mm from the apical foramen (D1), at the point of maximum root curvature (Dmc) and 7 mm from the apical foramen (D7). Canal transportation was assessed at 1 mm from the apical foramen in eight directions (MB, B, DB, D, DL, L, ML, M). The time it took to enlarge the glide paths for each group was also calculated. One-way Analysis of Variance was performed to assess if significant differences existed between the three groups for the variables being compared (p<0.05). A Bonferroni adjusted p value of 0.016 was used for pairwise comparisons of centring ability. K-files displayed statistically significantly higher centering ratios than G-Files at D1. At all levels the ProGlider file exhibited statistically significantly lower centering ratios than K-files. At Dmc, the ProGlider file demonstrated statistically significantly lower centering ratios than G-Files. Ratios were significantly similar between K-files and GFiles at D7 as well as between G-Files and the ProGlider file at D7 (p<0.016). Apical canal transportation for K-files was significantly more than G-Files in five directions and the ProGlider file in six directions (p<0.05). Glide path enlargement time for Kfiles was significantly slower (74.92 s ± 2.60 s) than G-Files (41.87 s ± 20.19 s) and the ProGlider file (27.95 s ± 8.55 s)(p<0.05). There was no statistically significant difference between glide path enlargement times of G-Files and the ProGlider file. Findings suggest that NiTi rotary glide path files are suitable for safe glide path enlargement because they cause less apical canal transportation than stainless steel hand K-files. Of the two NiTi rotary glide path file groups, the ProGlider file showed an overall significantly better centering ability around the entirety of the original canals, particularly at the point of maximum curvature. Glide path enlargement with the NiTi rotary glide path file groups was significantly faster than Kfiles (p<0.05).