Efficacy And Shaping Ability Of Different Rotary Nickel-titanium Instruments In Curved Root Canals

Objective To invesigate the shaping effects of two nickel-titanium rotary instruments on preparing curved canals in extracted molars.Methods 40 curved mesial canals of extracted lower milars, emveded in the Branmante models, were assigned to four groups:ProTaper difficult group, ProTaper general group, HERO 642 difficult group, HERO 642 general group . Apecal preparation was carried out till size 30. Straightening of canal curvature , the area of dentine removal, transportation of canal center, the change of shape factor, working time, file fractures were measured.Results the differences between the ProTaper groups and HERO 642 grounps in the pre- and post-instrument transportation of canal center are statistically significant. The area of dentine removed on coronal third, middle third cross section in ProTaper difficult group is bigger than in HERO 642 difficult group. There is no significance difference in the general groups. It is ststistically significant that the change of shape factor in ProTaper difficult group is bigger than HERO 642 general group.Conclusiohs The NiTi rotary instruments Hero 642 can be used for preparation of root canals effectively and safely, and is worth wide application.