The comparison of cyclic fatigue resistance of two different reciprocal files according to different access angles into the root canal

Aim: Root canal preparation is one of the most important steps of root canal treatment. Preparation procedure includes disinfection and shaping protocols. Ni-Ti rotary file systems are usually used for shaping. The biggest disadvantage of the usage of Ni-Ti rotary file systems is that the file gets broken during the treatment. There are many reasons for the breakage of files. One of the reasons may be the increase in the access angle. The purpose of this study is to compare the cyclic fatigue of reciprocating Reciproc and WaveOne Gold rotary systems according to different angles of accessing the root canal of Ni-Ti files. Methodology: In our study, 90 root canal files were used, 45 of which is Reciproc R25 (VDW GmbH, Munich, Germany) and the other 45 of which is WaveOne Gold Primary 25/07 (Dentsply, Maillefer, Ballaigues, Switzerland). Specially designed and manufactured stainless steel artificial roots whose curvature angle is 60° and curvature radius is 5 mm, which replicates the clinical conditions, were arranged. By enabling the files access the roots at 0°- 15°- 30° degrees, the lap numbers that they do till they break due to cyclic fatigue were examined. Results: When looking at the lap numbers that the Reciproc and WaveOne Gold root canal files do till they break, at accessing the roots at the same angles WaveOne Gold root canal file makes more lap numbers at all angles when compared with the Reciproc root canal file. Significant results were found when the groups were compared within one another and between groups and among all numeric data in the statistical analysis performed. It was also found that WaveOne Gold root canal file had more cyclic fatigue resistance. When the groups were compared within one another, it was found that the increase in the root access angle decreases the cyclic fatigue resistance of the files (p<0.05). No significant difference was found in the statistical analysis for comparison of the length of the broken file pieces (p=0.01). It was analyzed that when the broken files were examined via scanning electron microscope, file breakages occurred due to cyclic fatigue. Conclusion: Not only do the design features and production technology affect the breakage resistance due to cyclic fatigue of the root canal, the access angle to the roots affects the cyclic fatigue of the root canal files, as well.