两种镍钛器械预备根管后根管偏移的比较研究

目的：以锥束CT( CBCT)为研究工具评价TF和Pro-taper在预备离体牙弯曲根管中所产生的根管偏移。方法将按纳入标准收集的40个离体牙随机分为两组,用冠向下( crown-down)法预备,TF组预备至0．06/#25；Protaper组预备至F2。预备前后均用CBCT对离体牙近中、远中根管壁的厚度进行测量,然后利用Gambill 提出的公式进行根管偏移和轴中心率的计算。结果 TF组较Protaper组所需预备时间短,效率较高( P<0．05)；TF组和Protaper组器械在预备平均5个根管后都出现变形,无器械折断；在距根尖3、5、7 mm的内外侧壁所测得的根管偏移量比较中,TF组预备产生的根管偏移量小于Protaper组,而其轴中心率大于Protaper组,更接近于1。结论 TF在预备弯曲根管时能较好地维持根管原始形态,具有更高的效率；CBCT可在无创情况下评价预备器械对根管的成形能力。

A comparison between root canal deviations after root preparation using two kinds of nickel-titanium instruments

Objective To evaluate the root canal deviations in vitro teeth curved root with TF and Protaper instru-ments by cone beam computer tomography( CBCT) . Methods 40 teeth in vitro in the standard collection were ran-domly assigned to two groups, prepared with the crown-down method, the TF group ready to 0. 06/#25; the Pro-taper group ready to F2 . CBCT scans were taken to measure the mesial and distal thicknesses of the tube wall in vitro teeth before and after preparation. The root canal deviation and the rate of shaft center were measured with ref-erence to the formula proposed by Gambill. Results The TF group need less time in preparation and has more effi-ciency(P<0. 05) than the Protaper group; both TF and Protaper devices appeared deformation after 5 root canal preparations in average, no instruments broken. Comparing the offset of the internal and external wall of root canal in 3, 5, 7 mm from the apex, the root canal deviation prepared by the TF group was less than the Protaper group, and its rate of axis center was greater than the Protaper group, closer to 1. Conclusion TF can maintain original root canal morphology in preparing curved root canal, also has higher efficiency;under the noninvasive condition, the root canal forming ability of preparation instruments can be evaluated by CBCT.