Метод оценки вероятности поломки никель-титанового инструмента в зависимости от продолжительности его работы в условиях искривленного канала

• Format: Article
• Language: Russian
• Published: LLC "Endo Press" 2020-04-01
• Series: Эндодонтия Today
• Subjects: niti instruments; cyclic loading; breakage under cyclic loading; probability of breakage
• Online Access: https://www.endodont.ru/jour/article/view/759

The breakage of endodontic instruments during root canal treatment is a challenging problem which became even more critical after the introduction of NiTi instruments into clinical practice. The primary reasons of instrument breakage are torsion overloading and cyclic fatigue. In this article the results of experimental investigation under cyclic overloading are represented. Cyclic fatigue testing was performed using the glass models of the root canals corresponding to the curvature angle of 45° and the radius of curvature about 5 mm. The artificial canal models have been made of transparent glass tubes which allowed measuring the above mentioned parameters. The experiments have been accomplished on FlexMaster 25/.04 instruments for two configurations: 17 mm of working length and 2 mm pitch into curved part of canal, and 19 mm length and 5 mm pitch. 50 instruments were used for each case. Rotation time in the tube until the breakage at 300 rpm and the length of separated fragments were measured. These results allowed plotting the frequency distribution function of the time and then the probability value as the function of working time at the cyclic loading. It was shown for example that with a probability of 10% the working time is 53 sec for the 1-st experimental configuration (17 mm/ pitch 2 mm) and 67 sec for the 2-nd configuration (19 mm/ pitch 5 mm).