Comparative Study of Four Endodontic File Systems to Assess Changes in Working Length during Root Canal Instrumentation and the Effect of Canal Curvature on Working Length Change.

ABSTRACT

INTRODUCTION: The aim of this study was to compare a reduction in working length and area of canal enlargement resulting from instrumentation with Hedström (Kerr Dental, Orange, CA), K (Kerr Dental), ProTaper Next (Dentsply Sirona, York, PA), and TF Adaptive (Kerr Dental) files. The effect of the canal curvature on the working length and area of canal enlargement was also assessed. METHODS: A total of 80 plastic canal models were used, 40 with a canal curvature of 10° and another 40 with a canal curvature of 30°. Instrumentation of 10 models with a 10° canal curvature and 10 models with a 30° canal curvature was performed using each of the file systems up to size 25. Working length measurements were taken before and after instrumentation with each file type and size. Twenty composite images were made from superimposition of pre- and postpreparation photographs, and the difference in area was calculated using ImageJ software (National Institutes of Health, Bethesda, MD). RESULTS: ProTaper Next rotary files and TF Adaptive files produced the smallest reduction in the working length and the least canal enlargement followed by Hedström files and K files, respectively. The degree of canal curvature increased the working length reduction by a significant amount when K files and ProTaper Next rotary files were used, and the degree of curvature increased canal enlargement by a significant amount when K files were used. CONCLUSIONS: Nickel-titanium rotary files produced more favorable results than stainless steel hand files in terms of maintaining a consistent working length and producing minimal canal enlargement. Hedström files performed significantly better than K files in terms of working length reduction and canal enlargement.