Root canal preparation with the NiTi systems K3, Mtwo and ProTaper.

The aim of this paper was to examine the result of rotary root canal preparation with the nickel-titanium (NiTi) systems K3, ProTaper and Mtwo. One hundred and fifty curved artificial root canals and 60 mesial canals of human mandibular molars were selected. In the group of curved artificial canals, all canals were prepared to size 35/0.04 taper with the three systems. In the group of human mandibular molars, the teeth with mature root canals were radiographed with silver points inserted in bucco-lingual and in mesio-distal positions. In the artificial root group, one K3 instrument separated. Mtwo (20%) showed significantly (P = 0.003) less zips than K3 (46.9%) or ProTaper (50%). There were no significant differences in ledge and elbow formation. K3 and Mtwo had the lowest percentage of canal transportation. There was no significant difference regarding the preparation length or the condition of the apical foramina following the preparation. Canals prepared with K3 (26.5%) were significantly (P < 0.001) less tapered than ProTaper (62%) and Mtwo (82%). In the human mandibular molar group, one Mtwo and one ProTaper instrument separated. No significant differences were found in the preparation length, transportation or taper. The three systems tested, K3, Mtwo and ProTaper, achieved good preparation results.