This study is an attempt to evaluate surface changes and incidence of fracture of different single file systems (One shape and Neoniti) after root canal preparations of lower permenant molars, under different torques, using SEM.
Material and methods: - Total 26 files were used, 2 Control (one from each system),Group I (12 oneshape file) and Group II (12 Neolix files), each was further divided into Sub group A(low Torque) and Sub group B (High Torque)respectively. Results showed that even the new files suffered from surface defects.. No used instruments free of surface defects even under high or low torque. Different torques cause statistical significant difference between One shape and Neolix files in terms of disrubtion of cutting edge and metal flash only.
Conclusion Clinicians should be aware because all files are predisposed to wear and fatigue, so small files should have improved quality control by the manufacturer as they are highly prone to failure especially in curved canals or under high torque or single use.