| ObjectiveRoot canal therapy is the most effective method of pulp and periapical disease. Since the nineteen eighties, root canal therapy has gradually developed into a theory system, standard operation procedures, standardization of equipment and the effect of constant a preserve teeth treatment. In the past20years, medical science research foundation of root canal therapy has great development, has been greatly improved and the method of preparation of root canal, root canal filling materials and methods to further improve, especially a variety of modern technology, such as the application of operation microscope, significantly expanded the scope of preservation of teeth, root canal therapy clinical success rate can be up to above95%. Although the root canal therapy is the most effective method of pulp and periapical disease, but there are still a few failure cases need further treatment.Post-treatment endodontic disease (PTED) refers to the affected tooth root canal treatment of periapical lesions did not heal or the emergence of new diseases, the main clinical manifestations with root canal treated pain persists or periapical lesion prolonged does not heal. Its incidence according to the different countries and regions show about endodontically treated teeth35%-65%. If the cause of treatment failure is the root canal infections, nonsurgical root canal therapy is recommended. The success rate of nonsurgical root canal therapy has been estimated vary between74%-98%. The majority of cases, retaining the teeth may be the most favorable choice. Root canal residual necrotic tissue and bacteria are the main causes of failure of periapical inflammation and treatment. During root canal retreatment, the removal of gutta-percha and sealer is essential to allow the endodontic irrigants to contact and reduce the bacteria contained in the root canal space and dentinal tubules. Mtwo R and R-endo are two kinds of nickel titanium files designed for removal root canal filling. Chloroform is an organic solvent widely used to solubilise the gutta percha. The use of chloroform in dentistry has been controversial for its toxicity. The purpose of this study was to evaluate the efficacy of two kinds of nickel-titanium rotary instrument system versus stainless steel hand files for gutta-percha removal in single straight root canal with or without chloroform.Methods:60extracted single-rooted mandibular premolars were prepared by step-back technique and obturated by laterally condensed gutta-percha using AH-Plus as the sealer.4weeks after obturation the teeth were divided into6groups randomly. Removal of gutta-percha was performed with hand files, R-endo and Mtwo R respectively. All techniques were used with and without chloroform respectively. Following data were recorded:time to reach the working length(T1), time required for the removal of gutta-percha(T2), the amount of debris apically extruded(DAE). Then the teeth were vertically split and the cleanliness of the root canal walls was evaluated by Betti LV method.Results:In the groups without chloroform T1and T2were the lest (P<0.05) in Mtwo R Group. With chloroform T1and T2were the lest in R-endo group (P<0.05). In Mtwo R and R-endo groups with chloroform T1and T2were less than those without chloroform (P<0.05). In hand file groups T1was less when chloroform was used (P<0.05) and T2was similar (P>0.05) to that without chloroform. In Mtwo R and R-endo groups with chloroform DAE was less than that without chloroform (P<0.05). The differences of cleanliness of the root canal walls were not significant in all groups with or without chloroform.Conclusion: Chloroform may speed up the time of removal of gutta-percha from root canal and to decrease the apically extruded debrids, but can not improve the canal cleanliness in the application of Mtwo R and R-endo retreatment instruments. All instruments with or without chloroform produced similarly clean canals. |
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