The use of rotary instruments as auxiliary aids to root canal preparation of molars

One hundred adult extracted molars (292 canals) were apportioned into four groups of 25 teeth each. Group 1 was prepared using K-type files. Group 2 was prepared to size no. 25 with K-type files, followed by a no. 1 Peeso reamer, which enlarged the cervical third. The canal preparation was then completed with K-type files. Group 3 was identical to group 2 except that a no. 1 Gates-Glidden drill was used instead of a no. 1 Peeso reamer. In group 4, canals were prepared with the Giromatic method. All teeth were enlarged to size no. 30 to 35 in curved roots and size 40 in straight roots, at the apical stop level. Accurate silicone models were made of the preparations. A panel of seven endodontists rated the results according to the specific criteria of apical design, aberration removal, flow, taper, uniformity, and smoothness of preparation. The combination of K-type file and Peeso reamer or Gates-Glidden reamer preparations (groups 2 and 3) favorably met the foregoing criteria. Hand instrumentation and the Giromatic technique produced less favorable results.