Aim: To assess the shaping ability of ProTaper rotary nickel-titanium instruments in simulated canals. 

Methodology: A total of 40 simulated root canals consisting of four different shapes in terms of angle and position of curvature were prepared using the 'crown down' approach recommended by the manufacturer. Pre-operative images of each canal were recorded using an image analysis package, the simulated canals were prepared and post-operative images were taken following preparation to sizes F1, F2 and F3. The pre and post-operative images were then superimposed on the original images. Development of canal aberrations and transportations as a result of preparation were assessed together with a variety of other parameters including width measurements at standard positions along the canal length.

Results: Overall two instruments fractured (F1, F3) and 2 deformed (F3). None of the canals became blocked with debris. Five danger zones were produced, 3 after F1 and 2 after F2 and F3. Three perforations occurred (F3), 1 shoulder (F3), 3 ledges (F3) and 1 outer widening (F3). There were highly significant differences (p<0.0001) between canal types for total width measurements at standard positions along the canal length. There were highly significant differences (P<0.0001) between the canal types for the amount of resin removed from the outer aspect of the curve at the beginning of the curve, halfway to the orifice and at the orifice. There were highly significant differences (P<0.0001) between the canal types for the amount of resin removed from the inner aspect of the curve at the beginning of the curve and at the orifice. Following the use of F3 instrument, transportation toward the inner aspect of the canal occurred in 25 (64%) specimens at the beginning of the curve; all canals with 40º curves transported to the inner. Overall, transportation was towards the outer aspect of the canal except at the beginning of the curve.

Conclusions: Under the conditions of this study ProTaper instruments produced few aberrations following use of the F1 and F2 instruments. Further preparation up to the F3 instrument tends to straighten the canal and produce more aberrations.

Keywords: Pro-Taper; Canal Shape; Simulated Canals; Canal Aberrations; Nickel-Titanium; Rotary Instruments; Aberrations