不同镍钛根管预备系统对牙本质裂纹形成的影响

目的 探讨不同镍钛旋转预备系统ProTaper Universal（PU）、ProTaper Next（PN）和X+File（X+）对牙本质微裂纹形成的影响。方法 将100颗下颌前磨牙随机分为4组（n=25）。组1为对照组（不做根管预备）；组2为PU预备组（SX预备根管口，S1、S2、F1、F2预备直达工作长度）；组3为PN预备组（Protaper Universal SX预备根管口，再用ProTaper Next X1、X2预备直达工作长度）。组4为X+预备组（Protaper Universal SX预备根管口，然后用X+File X1、X2预备直达工作长度）。预备完成后，所有离体牙在距根尖顶点3mm、6mm和9mm处垂直于牙体长轴做横切片，在根管显微镜下观察并记录裂纹形成情况。卡方检验对裂纹形成数目进行统计分析。结果 对照组未产生牙本质裂纹。镍钛旋转系统PU、PN和X+的牙本质裂纹发生率分别为60%，32%和24%（P<0.05）。仅PU组产生完全裂纹，且数目高于另外3组（P<0.05）。在根尖1/3处，PU组的不完全裂纹数高于另外3组（P<0.05）。PN组和X+组的牙本质裂纹发生率无明显差异（P>0.05）。结论 本研究中使用的3种镍钛根管预备系统均产生了牙本质裂纹。其中，X+File与ProTaper Next产生的牙本质裂纹较少，这可能与镍钛金属结构、尖端设计以及中心定位能力有关。

Effects of different nickel-titanium root canal preparation systems on the dentin crack formation

Objective The effects of different nickel-titanium rotary systems of ProTaper Universal (PU), ProTaper Next (PN) and X+File (X+) on dentin cracks formation were investigated.Methods One-hundred mandibular premolars were chosen and divided into 4 groups randomly (n=25). Gr 1 was as control group (no preparation); Gr 2 was as PU preparation group (the coronal one-thirds of the canals were prepared with Sx and S1, S2, F1 and F2 instruments were used for the working length); Gr 3 was as PN preparation group (the coronal one-thirds of the canals were prepared with Sx and X1, X2 were used for the working length); Gr 4 was as X+ preparation group (the coronal one-thirds of the canals were prepared with Sx and X1, X2 were used for the working length). All the prepared roots were horizontally sectioned at 3mm, 6mm and 9 mm from the apex. The cracks were observed by endodontic microscope. The cracks formation was recorded and analyzed with a Chi-square test.Results No dentin crack was observed in the control group. The incidences of dentin crack formation in different nickeltitanium rotating systems of PU,PN and X+ were 60%, 32% and 24% respectively. Only complete cracks were observed in PU group and the number was higher than that in three other groups (P<0.05). At 3mm level, the number of incomplete crack in PU group was higher than that in three other groups (P<0.05). There was no significant difference in the incidence of dentin crack formation between PN group and X+ group (P>0.05).Conclusion All three different nickel-titanium rotating systems of PU, PN and X+ used in this study caused dentin crack formation. Among them, X+File and ProTaper Next produced fewer dentin cracks. Nickel-titanium structure, tips design and central location capability may be the reason for the less dentin crack.