The Clinical Application Of The Two Nickel-titanium Rotary System In Root Canal Therapy Of Molars

Pulpitis and periapical periodontitis are the commonly and frequently-occurring diseases in Stomatological Department, while the root canal therapy (RCT) is the preferred method to the treatment of pulpitis and periapical periodontitis.As an important step of root canal therapy(RCT), root canal preparation aims to clean and shape the root canal and to facilitate the filling. Root canal therapy included root canal preparation, root canal disinfection and root canal filling. Among them, root canal preparation is the most important ones. Whether root canal therapy succeed largely depends on the quality of root canal preparation. Modern concept of root canal preparation include clean-up and shaping of root canal. The goal for cleaning and shaping of the root canal system is to obtain a continuously tapering funnel from the coronal access (widest diameter) to the apex (narrowest diameter) that flows with the shape of the original canal. Preparation of the canal, especially the apical segment, without weakening the remaining dentin or perforating the root is essential to proper infection control and obturation and to long-term success. Stainless instruments, as the traditional instruments, have greater rigidity, the flexibility decrease with the increasing of the diameter of equipment, also it could lead to deviation of root canal easily and form the bench. The nickel-titanium device is a newly-rising root canal preparing system. It is efficient and well-shaping. It can shorten operating time and reduce tiredness,it also can get satisfied shaping and cleaning result in molar teeth canals.Objective:To evaluate clinical application of molar root canal preparation of the two Nickel-titanium rotary system:Mtwo and ProTaper. Methods:90molars from85patients fit for root canal treatment were divided into three groups, The A group used Pro Taper nickel-titanium rotary device and Crown-down technique for root canal preparing.The B group used Mtwo nickel-titanium rotary device and simultaneous technique.The C group used stainless steel K-files and the step-back technique. Three groups root canals were obturated by lateral condensation technique. The operating time was recorded. The efficiency of preparation was analyzed by radiographs before and after treatment. The incidence of instrument seperation and post-operative pain were recorded. All statistical analysis was performed using SPSS17.0software package. Data of root canal curvatures and preparation time was compared using analysis of variance. The incidence of complications of root canal treatment and postoperative pain and the efficiency of preparation and obturation were analyzed using Chi-square test.Results:The two Nickel-titanium rotary system could keep the curvature and flow of curved canals very well, and the continuously tapered root canal shape was achieved. There were no transportation, apical blockage, and ledge in all test groups. Post operative pain seldom occurred. Exact filling in the ProTaper and Mtwo groups were significantly higher than that in the stainless steel K-files group; The operative time of Mtwo was shorter than that of ProTaper. Five ProTaper rotary instruments fractured in canals. One Mtwo rotary instruments fractured in canals.Conclusion:ProTaper and Mtwo Nickel-titanium rotary system in root canal preparation can result in a very good maintenance of root canal anatomy and reduce postoperative pain, and it is time-saving and efficient.lt is worth of clinical application. Meanwhile, the problem of instrument fracture should be prevented.