SHAPING ABILITY OF NT-ENGINE AND MCXIM-ROTARY NICKEL-TITANIUM INSTRUMENTS IN SIMULATED ROOT-CANALS .2.

The aim of this laboratory-based study was to determine the shaping ab ility of NT Engine and McXim nickel-titanium rotary instruments in sim ulated root canals, A total of 40 canals with four different shapes in terms of angle and position of curve were prepared with NT Engine and McXim instruments, using the technique recommended by the manufacture r., Part 2 of this report describes the efficacy of the instruments in terms of prevalence of canal aberrations, the amount and direction of canal transportation and overall postoperative shape. Pre-and postope rative images of the canals were taken using a video camera attached t o a computer with image analysis software. The pre-and postoperative v iews were superimposed to highlight the amount and position of materia l removed during preparation, No zips, elbows, perforations or danger zones were created during preparation, Forty-two per cent of canals ha d ledges on the outer aspect of the curve, the majority of which (16 o ut of 17) occurred in canals with short acute curves. There were signi ficant differences (P<0.001) between canal shapes in terms of the inci dence of ledges, There were highly significant differences (P<0.001) b etween the canal shapes in total canal width at specific points along the canal length and in the amount of resin removed from the inner and outer aspects of the curve, The direction of canal transportation at the endpoint of preparation was most frequently towards the outer aspe ct of the curve, especially in canals with 40 degrees curves, At the b eginning of the curve, transportation in the majority of canals was to wards the inner aspect of the curve, Mean absolute transportation was less than 0.03 mm throughout the curve and towards the endpoint, with significant differences between canal shapes occurring at the apex (P< 0.05) and at the beginning of the curve (P<0.001), Under the condition s of this study, NT Engine and McXim rotary nickel-titanium instrument s created no aberrations other than ledges and produced only minimal t ransportation, The overall shape of canals was good.