关键词: 冠部预处理, 根尖偏移, 根管预备, 根管弯曲度

Abstract:

Objective    To study the effect of coronal preparing on the instrumentation of curved molar canals. Methods     Choose 121 patients who received treatment of extraction of the first and second molarsin 2006-2008 in Shenyang stomatology Hospital Oral Surgery due to periodontal disease（135 teeth， seventy-two extracted molars，with the degree of root canal curvature from12° to 35°）. According to Schneider measurement method of root canal curvatures they were divided into group of moderate bend （12  ~ 20°） and group ofsevere bend （21 ~ 35°）， each group of 36 root canals.Each group was then randomly divided into the test group and the control group， each group of 18 root canals. Test group： root canal crown was prepared with GG drill， conventional stainless steel of 10  ~ 35#. K for root canal preparation； control group：conventional method of root canal preparation. The standard digital radiographs were taken to record the position of the tip of the different sizes ， measure and compare the number of different groups filed after the apical preparation index （ATI） for statistical analysis. Results    Apical transportation  index of the test group of moderate group and severe curvature bending group by the coronal preparing was significantly less than the control group， the difference being statistically significant（P < 0.05）. The larger the files were， the greater the ATI became， and in the test group the cases of root perforations became less than in the control group. Conclusions    The effect of coronal preparing the root canals preparation for is much better than conventional treatment.

Key words: coronal preparing；apical transportation；root canal preparation；root canal curvature