[Preparation of curved root canals using hand instruments and mechanical aids]

Root canal preparation in curved canals was performed with handinstruments and three automated devices (Enac-Ultrasonic, Canal-Finder-System, Endolift). Ten curved roots canals in extracted teeth and 10 simulated curved canals in resin blocks were prepared with each device. The extracted teeth were cracked and investigated under the scanning electron microscope. Preparation with the ultrasonic system showed the best results in cleaning the middle and coronal part of the canal walls. The Canal-Finder-System gave the best results in maintaining the curvature of the canal. Hand preparation resulted in the best apical preparation. The use of the Endolift led to fractures of the instruments in four cases and to the worst results in cleaning the walls. With no method the canal preparation was perfect in form and cleanliness. Hand preparation should remain the standard method of root canals preparation. Nevertheless the use of automated devices such as Ultrasonics or the Canal-Finder-System may be helpful in certain strongly limited cases.