SHAPING ABILITY OF MITY-ROTO 360-DEGREES AND NAVIFLEX ROTARY NICKEL-TITANIUM INSTRUMENTS IN SIMULATED ROOT CANALS - PART 2

The aim of this study was to determine the shaping ability of Mity Rot o 360 degrees and Naviflex rotary nickel-titanium instruments in simul ated canals. Forty simulated root canals made up of four different sha pes in terms of angle and position of curvature were prepared by both sets of instruments using a stepdown approach. This study describes th e efficacy of the instruments in terms of prevalence of canal aberrati ons, the amount and direction of canal transportation, and thus the ov erall postoperative shape. Pre- and postoperative images of the canals were taken using a videocamera attached to a computer with image anal ysis software. The pre- and postoperative views were superimposed to h ighlight the amount and position of material removed during preparatio n. Neither Mity Roto 360 degrees nor Naviflex instruments created any zips or elbows. Ledges were produced in 20 (50%) canals prepared with Mity instruments and in 29 (72%) canals prepared with Naviflex instrum ents. Statistically significant differences (p < 0.001) between canal shapes occurred in relation to the incidence of ledges with 40 degrees canals (35) associated with more aberrations than 20 degrees canals ( 14); the position of the beginning of the curve had no effect. The dis tance of ledges from the end point of preparation was also affected si gnificantly (p < 0.01) by canal shape. Neither instrument created any perforations or danger zones. At specific positions along the canal le ngth, canal shape had a significant influence on total width and the a mount of material removed from the inner and outer aspects of the cana l curve. The direction of canal transportation at the end point of pre paration was most frequently toward the outer aspect of the curve in c anals prepared with Naviflex instruments, whereas the Mity instruments produced a more balanced preparation. At the apex and beginning of th e curve, transportation with both instruments was generally toward the outer aspect of the curve. Overall, mean absolute transportation was small and was below 0.1 mm at every position except the orifice. Under the conditions of this study, Mity Roto 360 degrees and Naviflex rota ry instruments prepared canals with a high incidence of ledges. Howeve r, in the absence of other aberrations, both instruments would seem to be a valuable addition to the endodontic armamentarium.