Canal shapes produced sequentially during instrumentation with Quantec LX rotary nickel-titanium instruments: a study in simulated canals

Aim The aim of this study was to determine the shaping ability of Quantec L X nickel-titanium rotary instruments in simulated root canals. Methodology Forty simulated canals consisting of four different shapes in t erms of angle and position of curvature were prepared with Quantec LX instr uments. Sequential still images were taken of the canals using a video came ra attached to a computer with image analysis software. Images were taken p reoperatively; after, instrument 7 (Size 25, 0.05 taper), instrument 8 (siz e 25, 0.06 taper), and instrument 10 (size 45, 0.02 taper) were taken to le ngth. Each sequential postoperative image was superimposed individually ove r the preoperative image in order to highlight the amount and position of m aterial removed during preparation. Intra-canal impressions after preparati on to size 10 were taken to evaluate three-dimensional canal form. Results Overall, the mean preparation time to size 10 was 4.7 min; canal sh ape did not have a significant effect on speed of preparation. No instrumen ts fractured within the canal, but 7 instruments separated from the latch g rip, and a further 3 instruments deformed. All canals remained patent. Foll owing preparation to size 10, 29 canals (72%) retained their length, 7 (17% ) lost length, and 4 gained length; the magnitude of the change in length w as always below 1 mm. Zips were created in 3 canals (7%) after use of size 10 instruments, but no perforations or danger zones were produced. Excess r emoval of material along the outer aspect of the curve between the beginnin g of the curve and the end-point (outer widening) was found in 22 canals (5 5%) after instrument 7, in 30 (75%) canals after size 8 and in 35 canals (8 8%) after size 10. There was a significant difference (P < 0.0001) between canal shapes for the incidence of this aberration at all sizes. Conclusions Under the conditions of the study, Quantec LX instruments tende d to remove excess material from the outside of the curve between the begin ning of the curve and the end-point. These aberrations increased in prevale nce and severity following the use of larger instruments when they were tak en to length. Size 8, 9 and 10 Quantec LX instruments should be used with c are and short of length, especially in severely curved canals.