| Curved root canal, especially severe curved root canal is not only important, but also difficult in root canal therapy. It is very easy to have the syndrome, such as instrument fracture, ledge, zipping, apical transportation, perforation because of the limitation of root canal morphology, endodontic instruments and root canal preparation methods. Endondontic failure may be the result of incomplete preparation and obturation, because the microorganisms and their metabolized substances penetrate through the gap between obturation materials and the wall of curved root canals.In view of specificity of curved root canal treatment, this study is to assess the sealing ability with different preparation methods, root canal sealers and obturation techniques by the quantitative methods using glucose(O-TB method) in vitro, which provides a theoretical guidance for clinical use.Objective:1. To evaluate the sealing ability of curved root canals prepared by different preparation methods2. To assess the sealing ability of gutta-percha points with lateral compaction technique, as used in conjunction with different root canal sealers.3. To assess the sealing ability of lateral compaction technique and vertical compaction technique using glucose penetration model.Methods:1. Sixty curved human maxillary anterior and premolar teeth were divided randomly into four experimental groups of twelve samples each and two control groups. The experimental groups were prepared by using the balanced force technique, ProTaper/crown-down technique, step-down technique, step-back technique and obturated by lateral compaction of cold gutta-percha with Cortisomol sealer. Control groups included six positive controls and six negative controls. Leakage along the root filling was measured by concentration of glucose in apical reservoir at thirty days with O-TB method.2. Sixty curved human maxillary anterior and premolar teeth were divided randomly into four experimental groups of twelve samples each and two control groups. The experimental groups were prepared by using ProTaper/crown-down technique and obturated by lateral compaction of cold gutta-percha with ZOE, Vitapex, Cortisomol, or AH-plus sealer. Control groups included six positive controls and six negative controls. Leakage along the root filling was measured by concentration of glucose in apical reservoir at thirty days with O-TB method.3. Sixty curved human maxillary anterior and premolar teeth were divided randomly into four experimental groups (A,B,C,D) of twelve samples each and two control groups. The group A and C were prepared by using ProTaper/crown-down technique. The group B and D were prepared by using step-down technique. The group A and B were obturated by lateral condensation with AH-plus sealer. C and D were obturated by Vertical condensation with AH-plus sealer. Control groups included six positive controls and six negative controls. Leakage along the root filling was measured by concentration of glucose in apical reservoir at thirty days with O-TB method.Results:1. Leakage was high in the positive controls and could not be detected in the negative controls. Mean the concentration of glucose for four experimental groups were(4.22±0.53), (4.51±0.70), (4.86±1.30) and (7.62±1.35) mmol/L respectively, there was significant difference between step-back technique group and balanced force technique, ProTaper/crown-down technique, step-down technique group (P< 0.05). The difference between balanced force technique group, ProTaper/crown-down technique and step-down technique group was not significant (P>0.05).2. Leakage was high in the positive controls and could not be detected in the negative controls. Mean the concentration of glucose for four experimental groups were(4.72±1.42),(4.07±0.89),(4.51±0.69)and(3.69±1.02)mmol/L respectively, there was significant difference between ZOE sealer group and AH-plus sealer group (P< 0.05). The difference between Vitapex, Cortisomol sealer group and AH-plus sealer group was not significant (P>0.05).3. Leakage was high in the positive controls and could not be detected in the negative controls. Mean the concentration of glucose for four experimental groups were(3.69±1.01),(4.59±0.98),(2.86±0.82)and (3.70±0.62)mmol/L respectively, there was significant difference between lateral condensation technique group and vertical condensation technique group (P<0.05). The difference between ProTaper/crown-down technique and step-down technique was significant when using different obturation techniques (P<0.05).Conclusion:1. The sealing ability of balanced force technique, ProTaper/crown-down technique and step-down technique is better than that of step-back technique in curved teeth in vitro.2. The sealing ability of AH-plus is better than ZOE, Vitapex, Cortisomol sealer in curved teeth in vitro at most observation time.3. The study showed that the sealing ability of vertical condensation technique is better than that of lateral at most observation time in vitro.
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