Gu Ying-xin, Zhu Ya-qin, DU Rong
Department of Oral Medicine, Ninth People's Hospital, School of Stomatology, Shanghai Second Medical University, Shanghai 200011, China.
Shanghai Kou Qiang Yi Xue. 2004 Oct;13(5):403-7.
To study the effect of coronal preflaring on the instrumentation of curved premolar canals.
Sixty extracted premolars, with the degree of root canal curvature from fifteen to thirty-five, were divided into fifteen sections in curvature sequence. After that, four canals of each section were randomly distributed to four different instrumentational groups. Two groups were coronally preflared with Gates Glidden drills first. Then they were instrumented by stainless steel or nickel titanium K-files from 15# to 40# with sequential preparation to working length. The other two groups were prepared directly with the above-mentioned two instruments. The standard digital radiographs were taken to record the position of the tip of the different sizes of instruments. At last, the curvature degrees were measured and the apical transportation indexes (ATI) were determined under stereomicroscope. t test or rank test for paired data was used for statistical analysis.
The curvature degree before and after instrumentation for each group was significantly different (P<0.01). The larger the files were, the greater the ATI became. The cases of root perforations in the stainless steel K-files group became fewer after coronal preflaring. The ATI of 30# for stainless steel K-files were much less after coronal preflaring, and were not significantly different with the ATI for nickel titanium instruments (P>0.05).
The effect of nickel titanium instruments was superior to that of stainless steel instruments by comparing the change of curvature degree and the ATI of preparing curved premolars root canals. Coronal preflaring should be performed first when the root canals were instrumented by stainless steel K-files or nickel titanium instruments with sequential preparation technique.
研究冠部预扩对弯曲前磨牙根管预备的影响。
60颗拔除的前磨牙，根管弯曲度为15°至35°，按弯曲度顺序分为15组。之后，每组的4个根管随机分配到4个不同的预备组。两组先用Gates Glidden钻进行冠部预扩。然后用15#至40#不锈钢或镍钛K锉按顺序预备至工作长度。另外两组直接用上述两种器械进行预备。拍摄标准数字化X线片记录不同型号器械尖端的位置。最后，在体视显微镜下测量弯曲度并确定根尖偏移指数（ATI）。采用配对数据的t检验或秩和检验进行统计学分析。
每组预备前后的弯曲度有显著差异（P<0.01）。器械型号越大，ATI越大。冠部预扩后，不锈钢K锉组的根管侧穿病例减少。不锈钢K锉30#在冠部预扩后的ATI明显减小，与镍钛器械的ATI无显著差异（P>0.05）。
通过比较弯曲前磨牙根管预备时弯曲度的变化和ATI，镍钛器械的效果优于不锈钢器械。当采用逐步预备技术用不锈钢K锉或镍钛器械进行根管预备时，应先进行冠部预扩。
