Nominal Size and Taper Analysis of Novel Metallurgy NiTi Files

The aim of this investigation was to assess the nominal tip diameter, taper and true pilot tip length of three nickel-titanium (NiTi) rotary files before and after use.

Three brands of NiTi files of size 25.08 were evaluated: ProTaper Uni-versal (Dentsply Tulsa Specialties, Tulsa, USA), Channels PT (Insight Endo for Henry Schein, Melville, NY) and ProTaper Gold (Dentsply Tulsa Specialties), with ten files from each brand (total n=30). Scanning electron microscope (SEM) images of the files at 50x magnification were acquired before and after the files were used on endodontic training blocks, and the images were analysed by two independent investigators using ImageJ software. The nominal tip diameter (D0), taper and true pilot tip length (measured as the distance from the advertised diameter size of the file to the tip of the file) were recorded for each file and were analysed for statistical differences using repeated measures of analysis of variance (r-ANOVA) and Tukey's post-hoc test (P<0.05).

The marginal means of the nominal size showed statistically significant differences between brands of the same size; statistically significant differences were also observed between the advertised sizes and the actual sizes (P<0.001). The mean taper values showed statistically significant differences from the advertised (p<0.001) sizes, except for the ProTaper Gold (P=0.023) group. The changes in the true pilot tip length before and after use were not statistically significant (P>0.05). The pilot tip lengths varied between brands.

All nominal tip diameters and most taper sizes of the analysed brands show statistically significant differences from the nominal sizes advertised by the manufacturers. The differences in true pilot tip lengths between brands indicate a current lack of standardization.