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Root-canal shaping with manual and rotary Ni-Ti files performed by students Delschen, Stephan Aim: To investigate root-canal shaping with manual and rotary Ni-Ti files performed by students. Methodology: Thirty undergraduate dental students prepared 150 simulated curved root canals in resin blocks with manual Ni-Ti K-files with a stepback technique and 450 simulated curved canals with rotary Ni-Ti files with a crowndown technique. Canal shape, preparation length, preparation time and incidence of fracture were investigated. Questionnaires were then issued to the students for registration of their rating of the two preparation methods. Results: Zips and elbows occurre significantly (p < 0.001) less frequently with rotary than with manual preparation. The correct preparation length is achieved significantly (p < 0.05) more often with rotary files than with manual files. The mean time required for manual preparation is significantly (p < 0.001) longer than that required for rotary preparation. Prior experience with a hand preparation technique is not correlated in an improved quality of the subsequent rotary preparation. Fractures are recorded in only 1.3% of cases with both rotary and manual preparation. 83.3% of the students claime to have a greater sense of security in rotary than in manual preparation. Conclusions: Inexperienced operators achieve better canal preparations with rotary instruments than with manual files. However, no difference in fracture rate is recorded between the two systems.