Instrumentation of root canals in molar using the step-down technique

By Goerig AC, Michelich RJ, and Schultz HH

Date: 01/1989
Journal: JOE


Purpose: To describe a technique for preparation of molar root canals. 

After access to the canal orifices is obtained, the coronal portion of the canal is enlarged with a step-down technique, and the apical preparation is completed with a step-back technique. 


•First, coronal access and development of a straight line path is made. •Radicular access is made by opening and flaring the coronal half to two- thirds of the canal to eliminate dentinal irregularities and pulpal tissue with Hedstrom files & GG burs. 

•H file sizes 15, 20, and 25 were used to a depth approximates the junction of the middle and apical thirds.

•Instrumentation with the step-down technique of radicular access is accomplished by decreasing lengths as the instrument diameter is increased. 

•Once the coronal and radicular access is obtained, the apical third of the canal is prepared. 

•WL must be determined before the step-back filing is started. 

•The apical portion is debrided with a no. 15 or no. 20 K-file to the apical foramen. An apical seat is established with a no. 25 file, 0.5 to 1.0 mm short of the apical foramen. Step- back is accomplished using K-files used in a reaming action, decreasing the length of successively larger files by 0.5-1.0 mm.

  •The apical seat is further defined with a no. 30 K-file or no. 35 K-file. Enlargement of the apical seat facilitates the placement of the master cone  •The completed root canal preparation has a continuous conical form that tapers to the apical seat.

Clinical significance: 

This technique simplifies apical instrumentation because immediate direct-line access to the apical third of the tooth is used, which increases the operator’s speed and the predictability of the final endodontic fill.