根管冠部预处理对前磨牙弯曲根管预备效果的影响

目的:研究根管冠部预处理对预备弯曲前磨牙根管时根尖偏移的影响。方法:将60个15°～35°的弯曲前磨牙根管按弯曲度排序后分成15个区组,每区组4个根管,再随机分配至4个不同处理组。其中2组根管冠部用GG钻预处理后,分别用不锈钢和镍钛合金K锉行常规法预备根管;另2个对照组直接行常规法根管预备;记录各组根管预备至不同锉号时的根管影像及器械尖端所在位置。最后,测量比较根管预备前后弯曲度的变化和不同锉根管预备后的根尖偏移指数(ATI)。采用t检验或配对资料的符号秩和检验进行统计学处理。结果:各组根管预备前后的弯曲度之间均有显著差异(P<0.01),ATI均随锉号的增大而增大。用不锈钢锉预备根管,经过冠部预处理,根管侧穿数目明显少于对照组,且30#锉所致的根尖偏移显著低于对照组(P<0.01),与同型镍钛合金K锉所产生的根尖偏移无差异(P>0.05)。结论:对于前磨牙弯曲根管,用镍钛合金锉预备,其效果优于不锈钢锉;不论是镍钛合金K锉还是不锈钢K锉,在用常规法预备弯曲前磨牙根管时,均应进行根管冠部预处理。

Effect of coronal preflaring on the instrumentation of curved premolar canals

PURPOSE: To study the effect of coronal preflaring on the instrumentation of curved premolar canals. METHODS: 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. RESULTS: 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). CONCLUSION: 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.