Evaluation Of Altering X-ray Projection Angulation For Successful Twin Canal Diagnosis In Mandibular Incisors

Root canal therapy is considered as the most effective way of dealing with diseases of the tooth root, dental pulp, and surrounding tissue,which is also the basis of diseased teeth conservation,with the meaning of avoiding inflammation in production.Thorough cleansing and high-containment is on the premise of thorough knowledge with the root canal morphology..Most mandibular incisors are treated as one root with single canal in the past.Along with the research that carried out,the complexity of root canal anatomy,number and regional difference in mandibular incisor has come to clinician's knowledge.In recent years,several scholars researched the root canal morphology of mandibular incisors in partial Chinese population. However,their attention were focused on root canal curvature and sectional morphology.In addition,their research were restricted by regional limits Walkar(1988) showed that the incidence of twin canals in mandibular incisors was 27% in Guangdong province and Hongkong.Yue Baoli et al.(1993) concluded that the incidence of twin canals in mandibular incisors was 21.4% in Shandong province,and later Wang Keqin and Wang Huiming did research in mandibular separately with results of 25.6 % in Tibet Autonomous Region and 14.2 % in Fujian province.There is no research about incidence of twin canals in mandibular incisors in Jilin province..Most twin canals lie in labia-lingual direction and angulated radiograph can improve diagnostic yield obviously.There are few researches about the angulation at which has both best diagnostic yield and clinical feasibility.This research will investigate the incidence of twin canals in mandibular incisors in Jilin province and determine the most effective horizontal agulation for successful twin canals diagnosis in mandibular incisors with radiologic method. IN order to determine the most effective horizontal agulation for successful twin canals diagnosis in mandibular incisors,the X2 test was applied to assess the significandce of the changes in paired data.Methods:153 human mandibular incisors were collected and cleaned in the region on Jilin province.Firstly,the teeth were radiographed from mesiodistal direction.Image were obtained and the incidence of twin canals were stated.Secondely,mandibular incisors with single canal were grouped randomly.Groups of three single canlal teeth with a twin canal mandibular incisors were placed to simulate the natural arch form of lower incisors in wax retained by a stock tray.The grouping teeth were radiographed at different horizontal angles from 0°to 50°(both left and right) at 10°intervals.Results: Vertucci grouped the types of root canals in mandibular incisor to five types according to root canal orifice quantity and the number of the root canal.Five observers analysed the radiographs.One observer was restorative and endodontics dentists with 10 year endodontic experience and four were seven year dental students.The results is that the incidence of twin canals in mandibular incisors in the region on Jilin province is 22.22%,and most of which is TypeⅢ(1-2-1). Five obervers analysed radiographs after angulated radiograph.The result is as follows: the greatest number were identified with a 30°left and 20°right angulation.The X2 test was applied to assess the significance of the changes in paired data.The test was applied to the following datas: 0°& 30°left and 0°& 20°right respectively.In 34 obervavations ,22 were incorrectly observed as single canal at the 30°left view. At the same time,12 were correctly observed as having tiwn canals at the 30°left view whilist being observed with a mean of 0.4 at the 0°view.The test gave a X2 of 6.80(P﹤0.05),which indicated that the 30°left view was highly significantly better than the 0°view.Similarly,the X2 value obtained from the data for 20°right was 6.07(P﹤0.05), which indicated that 20°right view was highly significantly better than the 0°view.Conclusions:There is a high incidence of twin canal with complex grouping and variance in mandibular incisors.It is necessary for clinicians to understand morphology of root canal in mandibular incisors completely before the root canal therapy.Angulated radiograph can improve twin canals diagnostic yield markedly.