| Background Root canal preparation as one of the key procedure which decide whether the root canal treatment will success or not.Usually preparing in the tap root canal system is ready to achieve satisfactory effect, but when prepare curved root canal, due to the complexity of root canal system, the physical properties of cutting equipment and operation technique of performer, easy to exist root canal wall perforation, steps formation, root canal deviation, the apex, root canal excursion to the bend side, and other complications affect curative effect.In recent years,nickel titanium tube apparatus with good flexibility, forming ability and unique memory performance and other significant advantages, is developing rapidly.Many studies have shown that, the use of nickel-titanium instrument in preparing root canal, can obtain more perfect taper, fewer tooth root canal perforation, more teeth retention and higher efficiency.And engine driven nickel-titanium alloy instruments which have been proven in keeping the root canal initial anatomical shapes is superior than stainless steel equipment, can shorten the operation time, reduce the performer’s fatigue.At present, the cone beam computed tomography is gradually applied in oral clinical, its advantages relative to the periapical film and panoramic radiographs technology gradually emerged, according to the specific area of scanning and digital processing, the area can be observed by non-invasive way to the mandible and maxillary, teeth, and the relationship with the surrounding anatomical structures, normal and diseased tissue through three dimensional image display, it can reflect the anatomical structure, guide the clinical treatment and prognosis more intuitively and clearly.Purpose Engine driven Twisted File(TF) and Pro Taper nickel-titanium root canal instruments can be used in root canal preparation, preparation were proved to have good consequence in mild-to-moderate curved root canal.In this experiment, using cone beam CT(CBCT) as a research tool, measure the change of root canal wall inside and outside after TF and Protaper prepared in vitro teeth moderately severe curved root canal, calculate the root canal deviation emerged after TF and Protaper preparing in vitro teeth moderately severe curved root canal, evaluate the forming ability of TF and Protaper in preparing curved root canal,aim for guiding the clinical application.Methods This study collected the mandibular premolar and molar teeth pulled for orthodontic or periodontal disease between September 2013 and February 2014 in our hospital. 40 teeth in vitro in the standard collection were randomly assigned to two groups(the TF proup and the Protaper group), prepared with the crown- down method, the TF group ready to 0.06 / # 25; the PT group ready to F2. CBCT scans were taken to measure the mesial and distal thicknesses of the tube wall in vitro teeth before and after preparation. The root canal deviation and the rate of shaft center were measured with reference to the formula proposed by Gambill.Result 1. The time of root canal preparation and the deformation and broken of root canal preparation instruments The TF group need less time in preparation and has more efficiency(P < 0.05) than the Protaper group; Both TF and Protaper devices appeared deformation after 5 root canal preparations in average, no instruments broken. 2. Comparing the root canal deviation and the rate of shaft center of the two groups Comparing the offset of the internal and external wall of root canal in 3, 5, 7 mmfrom the apex, the root canal deviation prepared by the TF group was less than the Protaper group, and its rate of axis center was greater than the Protaper group, closer to 1. 3. Comparing the root canal deviation in different sections of the two groups In the TF group, the average of internal dentine removal was slightly smaller than the average of external in the section 3 mm and 7 mm distant from the root apex, and the average of internal dentine removal was slightly bigger than the average of external in the section 5 mm distant from the root apex, no statistically significant difference were observed in the comparison between the two groups;In the Protaper group, the average of internal dentine removal was slightly smaller than the average of external in the section 3 mm and 7 mm distant from the root apex, and the average of internal dentine removal was slightly bigger than the average of external in the section 5 mm distant from the root apex, the difference in the comparison of the section 3 mm and 7 mm distant from the root apex was statistically significant(P < 0.05).Conclusion TF can maintain original root canal morphology in preparing curved root canal, also has higher efficiency; under the noninvasive condition, the root canal forming ability of preparation instruments can be evaluated by CBCT. |
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