Assessment of Distortion and Separation of New Rotary Ni-Ti Files under Clinical Standardized Simulation: A New Method

Abstract

Aim: A consideration was given in the present study to construct a device to minimize variables related to the instrument usage as speed, torque, time, and number of instrument usages. In addition, to evaluate the distortion/separation of two root canal instruments introduced with claims of improving their fracture resistant. A special device was constructed to standardize experimental variables in clinical simulation including speed, torque, time, and pressure. The testing device consists of two main parts: mechanical and electrical. A Dc Electric motor and two micro-switches connected to the mechanical and electrical components and an electric gear motor with a 1:16 reduction contra-angle hand piece. Materials and methods: Freshly extracted mandibular and maxillary molars with mature apex were collected n=180 root canals. Mesial root of mandibular molars and buccal roots of maxillary molars were separated using diamond disc under coolant. Dissection of the crown above cervical line to provide a standard working length from the apical end of root at 14-mm was maintained for all selected teeth. Size 15 stainless steel K- hand files; initial apical file (IAF), in reaming motion was used to initiate a glide path in all selected samples. File (IAF) was inserted in the canal, radiographed mesio-distally (buccal view) using RVG angle of curvature was estimated according to Schneider method. The roots were grouped according to curvature into two groups group A (15-25) and group B (26-35) degree of curvature. These two groups were equally subdivided into two subgroups each according to the rotary files to be tested; the RaCe files and TF fil