SHAPING ABILITY OF LIGHTSPEED ROTARY NICKEL-TITANIUM INSTRUMENTS IN SIMULATED ROOT CANALS. 2

The aim of this laboratory based study was to determine the shaping ab ility of Lightspeed nickel-titanium rotary instruments in simulated ro ot canals. A total of 40 canals with four different shapes in terms of angle and position of curve were prepared with Lightspeed instruments using the stepback technique recommended by the manufacturer. This re port describes the efficacy of the instruments in terms of prevalence of canal aberrations, the amount and direction of canal transportation , and overall postoperative shape. Preoperative and postoperative imag es of the canals were taken using a video camera attached to a compute r with image analysis software. The preoperative and postoperative vie ws were superimposed to highlight the amount and position of material removed during preparation. Only one (2.5%) zip and one elbow were cre ated, with no ledges, perforations, danger zones, or blockages being p roduced. At specific points along the canal length there were highly s ignificant differences (p < 0.001) between the canal shapes in total c anal width and in the amount of resin removed from the inner and outer aspects of the curve. The direction of canal transportation at the en d point of preparation was most frequently toward the outer aspect of the curve; although in half of the canals, transportation was either d irected toward the inner aspect or not observed. At the apex of the cu rve, the beginning of the curve, and halfway to the orifice, transport ation was reversed with the majority of canals being transported towar d the inner aspect of the curve. Mean absolute transportation was smal l and was below 0.06 mm at every position except the orifice. Overall, Lightspeed rotary instruments prepared canals well and would appear t o be a valuable addition to the endodontic armamentarium.