| Root canal therapy is the basic and most optimal curing method of pulp diseases and apical diseases. As an important step of root canal treatment, root canal preparation aims to clean and shape the root canal and to facilitate the filling. The narrow and curved root canals bring about many difficulties during the process of the preparation clinically. Fortunately, the introduction of the nickel titanium device makes the preparation of root canal effective and efficient. Compared with the traditional stainless devices, the nickel titanium ones have the advantages of greater resistance to fatigue and fewer postoperative complications. It has been widely acknowledged that Profile brand is the best of its kind. Though there are reports about the clinical merits of Profile rotatory device, there has hardly been any paper available on its long term effect up to now. This study observed the change of curvature and shape in the simulated root canals after the preparation with Profile rotatory device, evaluated the safety factor and working time on the extracted molars, analyzed the cleaning effect of root canals by scanning electron microscope study, K file was used as control, and the work was carried on the self-made stainless model after the design of Hulsmann M, with the exception of the clinical observations. The aim of this work was to provide advice for dentists in the use of Profile rotatory device. The results of the study are as follows: 1. Effect of Profile rotatory device on the curved root canal (1) The analysis of root canal curvature and shape preparated with Profile rotatory device50 simulated curved root canals curving around 38?were equally and randomly divided into two groups, the experimental group and the control group. All samples were embedded in the stainless model with epoxy, and hardened in the 37 C, 100% humidity environment for 24 hours. The root canal curvatures were measured in the preoperative radiographs with a size 15 reamer inserted. The experimental group was prepared with Profile rotatory device up to size 30 using crown-down technique, while the control group was prepared with K file using the traditional technique up to size 40. The curvature of the postoperative root canals was measured in the radiographs with a gutta percha inserted. The analysis of the changes of the curvature and the shape with light microscoperesults tended to show that Profile rotatory device could maintain the curvature and shape of the root canal.(2) The analysis of the safety factor and efficiency of Profile rotatory device80 newly extracted mandible first and second molars with separated, curved mesial buccal and lingual root canals were embedded in stainless model with the method as described above. The curvature of the root canals was measured in radiographs with a 10 size K file inserted. 50 root canals with the curvature greater than 15 degrees were randomly divided into two groups. The preparing technique was the same as the experiment mentioned above. The working time and the ratio of the device fracture was recorded and statistically analyzed. The results showed that the Profile rotatory device worked more efficiently but had higher ratio of device fracture. It seamed to suggest that the operator should abide by the protocol strictly and the use of Profile rotatory device combined with K file might lead to better results.2. The SEM evaluation of root canal preparation using Profile rotatory device and K fileThe purpose of this part of the study was to compare the cleanliness of the root canal walls prepared by K file and Profile rotatory device by using scanning electron microscope. 4 extracted cariesless molars with curved root canals (curving around 15 degrees) for periodontal reasons were randomly divided into 2 groups of two samples each. All the samples were embedded in the self-mademodel after the design of Hulsmann M. One group was prepared with K file and the other with Profile rotatory device. After that, the root canals were cut longitudinally and processed f... |
