SHAPING ABILITY OF LIGHTSPEED ROTARY NICKEL-TITANIUM INSTRUMENTS IN SIMULATED ROOT CANALS .1.

The aim of this study was to determine the shaping ability of Lightspe ed nickel-titanium rotary instruments in simulated canals, Forty canal s consisting of four different shapes in terms of angle and position o f curvature were prepared by Lightspeed instruments using the techniqu e recommended by the manufacturer, This report describes the efficacy of the instruments in terms of preparation time, instrument failure, c anal blockages, loss of canal length, and three-dimensional canal form , Overall, the mean preparation time for all canals was 8.12 min with canal shape having no significant effect on the speed of preparation, No instruments deformed or separated during the study, and none of the canals became blocked with debris, Seventeen canals retained their or iginal working length, but 16 gained in length and 7 lost length. Ther e was no significant difference between the canal shapes in terms of t he mean loss of distance or category of distance change, Apical stops as judged from intracanal impressions were present in 23 of the canals but they were all judged to be of poor quality, The canals were found to be smooth in the apical half of the canal in 36 specimens and in t he coronal half of 24 specimens, All the canals had poor taper charact eristics, and only 16 specimens showed good flow characteristics. Unde r the conditions of this study, Lightspeed instruments prepared canals rapidly, with no fractures, canal blockages, and with minimal change in working length, The three dimensional form of the canals was compro mised as flow and taper were less than ideal, presumably as a result o f an ineffective stepback procedure, The results imply that either the stepback sequence should be modified or another instrument with incre ased taper should be used to refine the canal walls before obturation.