Effects Of Different Root Canal Preparation Systems On The Formation Of Defects In Root Dentin

Endodontics and oral periapical diseases are common diseases, seriously harm to human oral health, affecting the normal function of the masticatory system. Now the preferred method is root canal therapy, the treatment process includes pulp open, root canal preparation, root canal disinfection and root canal filling. Among of them, the root canal preparation is the critical step of root canal therapy, success of root canal therapy largely depends on the quality of root canal preparation. Root canal preparation is to clean the tissue lesions and their decomposition products, bacteria and toxins of pulp. Expand the root canal and form the final shape, remove the infected dentin from surface of root canal wall and prepare the root canal as the shape which diameter of the root canal orifice is largest, dentino-cemental junction is smallest, smooth and tapered. Rinse the root canal, removing debris and residual material from the root canal. Today NiTi files with machine are used common in root canal preparation. NiTi files with machine can better remove infected dentin of root canal wall and microorganism, forming with high speed, but at the same time have an impact on dentin of root canal wall is a major concern in recent years. Researches of this issue are mostly foreign. Due to the differences between races and regions, resulting in different anatomy of teeth, foreign data of researches have less meaning to people in our country. In this study, we collected maxillary premolars with single root and double root canals. With four different root canal preparation systems, spiral CT scanning the teeth, and diamond inner circle slicer slicing method to observe the impact of dentin of root canal wall caused by different systems after the process of root canal preparation. Provide new ideas in selecting preparation system and methods in the course of clinical root preparation.Objective:Collected maxillary premolars of people from our country with a single root and double root canals. Use four different system files to prepare. Use spiral CT scan and diamond inner circle slicer to observe the differences between the four systems.Methods:â‘  Method of spiral CT:Select 100 maxillary premolars of people from our country with a single root and double root canals, randomly divided into five groups, each group with 20 teeth, labeled number. Every tooth was scanned by DISCOVER CT750 spiral CT, and the initial images were recorded. One dentist used four different systems files for root canal preparations. Spiral CT scanned teeth again, and recorded the images. Two dentists compared the images before and after root canal preparation. â‘¡Method of diamond inner circle slicer:Used diamond inner circle slicer incise 100 maxillary premolars which Spiral CT had scanned after root canal preparation at a level of 3mm,6mm,9mm from apical. Two dentists observed vitro teeth sections under the stereo microscope, recorded cracks and craze lines, analyzed data with statistical methods.Results:â‘  Observed the Spiral CT images of100 maxillary premolars with a single root and double root which the teeth has took root canal preparation of canals, the images of crack or other craze lines are not observed.â‘¡Overall, instrumentation with Reciproc Files was associated with significantly more cracks with HF, ProTaper and Oneshape(P=0.019). No significant differences were obtained between HF and ProTaper (P>.05). Oneshape has difference between HF, ProTaper, also has difference with Reciproc (P<0.05)â‘¢ In general level, there is a significan tdifference between four groups files. Reciproc generated more craze lines than HF, ProTaper and Oneshape at the level of apical 3mm(P<.001).At the level of 6mm, Reciproc and Oneshape generated more craze lines than HF and ProTaper.(P<.0024)At the level of 9mm, there is no difference between ProTaper, Oneshape and Reciproc (P=0.725)â‘£We did not find tooth with crack and craze line in the group of control and HF, but we found the teeth with crack and craze line in the group of ProTaper, Oneshape and Reciproc.Conclusion:In root canal preparation process, a single nickel titanium file system Reciproc causes more cracks and other craze lines at the level of apex than ProTaper and Oneshape with several files. In the clinical course of root canal operation, assessing the root canal anatomy system according to the X-ray, CT and other radiological means before treatment, select the appropriate files and means before root canal preparation. Get a better root canal preparation to improve the cure rate.