Influence of Canal Geometry on the Mechanics of Nickel-Titanium Endodontic Rotary Instrumentation

• Main Authors: Fang-Yu Liao, 廖芳瑜
• Other Authors: Weng-Pin Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/11756070878800053236

碩士 === 中原大學 === 醫學工程研究所 === 95 === The important objectives of endodontic treatment are to achieve good canal shaping and cleaning. The goal of shaping is to attain a continuous taper from the coronal access to the apex. In recent years, Ni-Ti alloy has been used widely for endodontic instruments due to its bio-compatibility, high flexibility, and stronger in fatigue resistance than stainless steel in curved canal treatment. It is known that changes in the shape of instrumentation in curved canal may have a crucial influence on the success of root canal treatment and may cause instrument fracture. In clinical practice, many of the instrument fractures happen unexpectedly with no visible sign of permanent deformations. It is a serious concern in root canal preparation. Therefore, the purpose of this study was to investigate the influence of canal geometry on the mechanics of Ni-Ti endodontic rotary instrumentation by using finite element analysis and to provide suggestions for product designs. The current thesis was divided into three main parts. Part 1: The tip of ProTaper Universal System file was pressed down by a wedge-shaped block and the stress distributions were analyzed. Results indicated that ProTaper Universal System file has better bending-resistance ability than Protaper System file. Part 2: first, the stress distributions of files pushed into different types of 2-D curved routes were compared. Three different angles of curvature (20°, 40°, 60°) and three different radii of canal (5mm, 7.5m, 10mm) were considered, respectively. Second, we compared the effects of different canal geometries on the file stress distribution. Three different starting locations and extents of curved canal (coronal, middle and apical part) were considered. Also, different diameters of root canal orifice enlargement (1.3, 2, and 2.6mm) were taken into account. Results indicated that when under the condition of an increase in the radius of curvature, a decrease in the curvature extent, a decrease in the starting curved distance, and an increase in the root canal orifice diameter, it will lead to a decrease in the maximum principal stress of the file. The curvature of file was decreased when the staring curvature distance decreased from the root canal foramen. But the variation of curvature is not obvious when both the root canal orifice was enlarged and the staring curvature distance was decreased from the root canal foramen. Part 3: A new type of file was designed and analyzed. The smooth area of the file was replaced by a threaded and tapered part. The results revealed the stress was reduced and therefore it is suggested that sharp variation should be avoided when designing root canal files in order to reduce stress concentration.