Effect on Working Length in Curved Canals after Coronal Flaring Using Hand Stainless Steel and Rotary Ni-ti Files: An in vitro study

Effect on working length in curved canals

Abstract

Context: Maintaining the uniformity of working length measurement throughout the course of endodontic treatment is crucial to achieve the desired outcome of endodontic treatment and its long term success; in spite of various methods available to establish the correct working length. This is particularly critical in the instrumentation of curved canals.
Aims: Assessment of effect on working length in curved canals after the coronal flaring using hand stainless steel and rotary Ni-ti files.
Material and Methods: 40 extracted human maxillary and mandibular; first and second molar teeth were selected of which only the mesial root of mandibular molars and the mesiobuccal root of the maxillary molars were considered for the study. All the specimens were ranked by degree of maximum canal curvature and divided into two groups ranging from 20-45°. The roots demonstrating the smallest curve were assigned to group 1, the next smaller curve roots were assigned to group 2. The conditions compared were combinations of (a) early coronal flaring(flaring completed before WL determination) and late coronal flaring (flaring completed after WL determination) and (b) stainless steel hand files_Gates Glidden drills (SS) and nickel titanium rotary files (Ni-Ti).
Results: Results indicated that WL decreased for all canals as a result of canal preparation. The mean decrease in WL was significantly greater for the Stainless steel group than for the Ni-Ti groups. Less change in WL occurred in all groups when initial WL was determined after CF.
Conclusions: Results concludes that Ni-Ti rotary files can be expected to consistently produce a small decrease in WL, whereas the combination of G. G. Drills and stainless steel files causes more than twice as much decrease in WL.