[Clinical effect of three kinds of rotary nickel-titanium instruments on root canal preparation of molars].

PURPOSE: To evaluate three kinds of nickel-titanium instruments applied to molar root canal preparation. METHODS: A total of 90 molars treated by root canal therapy were randomly assigned to three groups: ProTaper group. K3 group and Mtwo group. Crown-down technique was used in ProTaper and K3 group, while Mtwo group was treated with routine preparation technique. All teeth in 3 groups were filled by lateral condensation technique. Treatment effect of 3 groups was evaluated according to pre- and post-operative X-ray films. Wearing and tearing degree of equipment, preparation time and postoperative complications incidence of 3 groups were also compared. All statistical analysis was performed using SAS9.0 software package. Data of root canal curvatures and preparation time was compared using t test; the incidence of complications of root canal treatment and postoperative pain was analyzed using Chi-square test. RESULTS: In three groups, root canals had no deviation or no ledge, could maintain the root canal anatomy in early form, and achieved good preparation results. In this study, four ProTapers, three K3s and one Mtwo instrument were fractured. The average root canal preparation time of the Mtwo group was 3.94 min, significantly less than the ProTaper (4.71 min) group and the K3(4.58 min) group. CONCLUSIONS: Three rotary nickel-titanium systems tested in this study are effective in the molar root canal preparation. The Mtwo instrument is much easier and faster during preparation with routine preparation technique.Supported by Research Fund of Science and Technology Commission of Shanghai Municipality(Grant No.08DZ2271100).