| Background:Root canal therapy is the most fundamental and effective treatment for pulp disease and periapical disease. In the impact factors of root canal filling, root canal preparation and shaping is the key point. The cleaning efficiency of root canal preparation instruments in the comparative research has been the focus of scholarly research. It is proved that the traditional preparation instruments such as K files need more time and require strenuous efforts. They may easily cause apical perforation and transportation, so the removals of infectious materials are not thoroughly, the root canal preparation is not satisfied. All of these lead to the recurrence of inflammation, which brings the failure of root canal therapy.In recent years, hand-used nickel-titanium (Ni-Ti) instruments and rotary Ni-Ti instrument system have been gradually used for enlarging root canals in root canal preparation. Protaper (Dentsply Company) is the typical Ni-Ti instrument. The Ni-Ti instruments can prepare root canals effectively and quickly. They can remove the residual infectious material in root canals, so the perfect root canal preparation arrive easily; meanwhile, the Ni-Ti instruments especially the rotary Protaper system can shape root canal quickly and efficiently, reduce fatigue of dentist. Therefore, lots of researches have been done on the effect of canal shaping and enlargements which were done by Ni-Ti instruments. However, seldoms of them pay enough attention to the influence on clinical assessment of filling canals shaped by Ni-Ti instruments.At present, periapical x-ray system has been the most widely used and practical detection, which reflects the sealing ability in filled canals. There are also many other methods to detect the sealing ability, such as microscopy, micro-CT (microcomputed tomography), periapical microleakage evaluation, oral computed tomography (CT). Because of high costs, ionizing radiation, difficult operation in clinic, the periapical x-ray system is still the most extensively evaluation method which detects the sealing ability of root canal obturation. The two-dimension periapical x-ray system evaluation cannot fully reflect the three dimension form of root canals, the sealing ability of filling canals which have the lateral root canals, oval root canals. In this study, the influence on sealing ability of filling canals shaped by hand-used Ni-Ti instruments and rotary Ni-Ti instrument system is explored. Meanwhile, the contrast study is carried out to discuss the consistency of sealing ability in filled canals detected by periapical x-ray system and CT, so that the quality of obturation in root canals shaped by Ni-Ti instruments can be more comprehensively understood and evaluated.Purpose:To detect the sealing ability, filling effect of root canals prepared by using Ni-Ti hand-used Protaper and Ni-Ti rotary Protaper system by x-ray and CT scan, and comparing the influences and the differences in judgment of the two detection methods on sealing ability during root canal therapy.Methods:1. Experimental materials The subjects of this research are sixty-four anterior teeth or premolars with one root canal, all of which were extracted because of orthodontic demand or periodontal disease. The teeth were divided into two groups at random; each group has thirty-two teeth. The root canals preparation instruments were hand-used Protaper and rotary Protaper system. Cold gutta-percha lateral condensation filling technique was used for root canal obturation. After root canal filling, zinc was filled in each tooth, and finally, glass ionomer was put on the surface to complete the coronal restoration.2. Methods(1) Methods of root canal fillingIn this experiment, the procedure of root canal filling was conducted in accordance with the teaching materials--, which was the National Eleventh Five Year Plan of oral teaching undergraduate. The chief editor of the teaching materials was Wenming Fan. First, access cavity, use number 15 k-file to penetrate each root canal, and then get the working length, according to the assigned group, prepare root canals by different instruments, obturate the root canals with cold gutta-percha and AH-plus paste by lateral condensation technique.(2) Evaluation of the sealing ability of filling canalsEach tooth was marked with the hand-used group or rotary system group separately. Each filled teeth was screen by CT and shoot with periapical x-rays. We detected the sealing ability of filling root canals at the cross-sectional planes which had distances to apical foramen 3 millimeters,7millimeters,10 millimeters. (It delegates one third apical canal, one third middle canal, one third coronal canal as well.) The results of apical x-ray system used the visual inspection. On the other hand,the results of CT were calculated by the software Ez3D2009 3D CD Viewer Ver.1.2.0.0. That software analyse the total area of voids in the percentage of whole root canal cross-sectional area. At last, we had all the data statistically analyzed and compared,that included the sealing ability of filling canals in every tooth's one third apical canal, one third middle canal, one third coronal canal of each group.Results:1. There was a significant difference in sealing ability of one third apical filling canals shaped by hand-used Protaper and rotary Protaper system(p<0.05); there were no significant difference in sealing ability of one third middle, one third coronal filling canals shaped by hand-used Protaper and rotary Protaper system(p>0.05). The Ni-Ti rotary Protaper system enlarged and shaped canals significantly better than the Ni-Ti hand-used Protaper in one third apical root canal; the Ni-Ti rotary Protaper system also can significantly improve the efficiency of root canal preparation, the sealing ability of apical filling canals,2. By the McNemar test, notable difference were seen between CT three-dimensional cross-section segment detection and visual apical x-ray system detection about the sensitivity of determination on the sealing ability of filling canals'apical third, middle third, coronal third section(p>0.05).CT detection can find the inadequate filled canals which were caused by lateral root canals, oval root canals, and canal internets in middle and apical third root canals. The performances in sealing ability of CT detection were much better than apical x-ray system.Conclusions:1. The Ni-Ti rotary Protaper system enlarged and shaped canals better than the Ni-Ti hand-used Protaper in one third point apical root canal; the root canals shaped by rotary Protaper system acquire better apical sealing than that shaped by hand-used Protaper. The rotary Protaper system were comparable to optimally enlarge root canals with minimal apical perforation and transportation, maintain the direction and curvature of root canals.2. CT detection was obviously more accurate than apical x-ray system in testing sealing ability of filling canals. The apical x-ray system has shortage in reflecting the sealing ability of filling root canals accurately. Sometimes, there were obvious deviations because of lateral canals, canal internets of apical and middle third root canals, manual apical perforation and transportation and so on. |
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