Three-dimensional Analysis of Cutting Behavior of Nickel-Titanium Rotary Instruments by Microcomputed Tomography

The cutting behavior of nickel-titanium rotary instruments with and without irrigation was evaluated in a bovine bone model. Six brands of NiTi rotary instruments were constrained into a curved trench. The tips of the instruments were bent to create a 1-mm long initial contact with the floor of the trench. After a series of 100, 200, 300, 400, and 500 (1,500 total) push-pull strokes on each rotating instrument, the grooves were scanned by microcomputed tomography. The volume of removed material and the maximum depth of the cut groove were measured. Irrigation increased the cutting efficiency of the instruments significantly, except for Liberator (Li). There was a significant correlation between the extracted volume and the maximum depth. The volume removal rate was highest with K3 and Li (dry) and with K3 and FlexMaster (FM) (irrigation group). The maximum cutting depth was highest with FM and K3 in both dry and irrigation groups. The cutting behavior of NiTi rotary instruments depends both on experimental setup, instrument design, and cutting condition.