The Endodontic Glidepath: “Secret to Rotary Safety”

[Anonymous]

The fourth skill for consistent Glidepath preparation is to understand and master the 4 manual motions to prepare the rotary Glidepath.
1. “Follow.” Identify the entrance to the canal and remove any dentin or enamel triangles that are preventing straight-line access. Irrigate thoroughly with sodium hypochlorite before gently “slipping and sliding” down the canal (Figure 14). If a plug of dentin covers the orifices that have been identified using ultasonics, high-speed burs, or Mueller burs, first agitate chamber sodium hypochlorite using EndoActivator (DENTSPLY Tulsa Specialties). Then dense orifice dentin will be removed or softened, and small files can penetrate easily and the “following” motion can begin. Take the smallest file that fits the canal easily, and slightly precurve the apical a few millimeters using metal cotton pliers. If you are using a microscope, hold the handle of file with cotton pliers so your fingers do not block the line of sight to the orifice. Once the file can stand upright in the canal on its own, “follow” the file down the canal. Allow it to go whatever direction it wants. Be intentional about reaching the RT but stop attempting to “follow” short of maximum resistance and implement the No. 3 motion called “Envelope” (described below). When following to the RT, use watchwords such as gentle, caress, slip and slide, stroke, trail, and restraint. If RT is reached easily with the first “follow,” identified with apex locator and validated with radiographic or digital image, then proceed with manual motion No. 2: “Smooth.”

2. “Smooth.” Once RT file position has been validated, make short amplitude vertical stokes until the file is loose. This may mean a half a dozen strokes or it may mean 100 strokes. Whatever it takes, do it. If the file is at first too tight to easily make short strokes, ie, the file is apparently binding against 2 or more walls, then wiggle the handle left and right without any up or down motion. This simple, safe nuance will wear away the small amount of restrictive dentin and free the file for the smoothing motion. The minimal Glidepath file size for safe rotary shaping is a loose No. 10 file. While many endodontists prefer a larger file (55%, as noted in my spring AAE 2010 survey), every increase in size while making a theoretically bigger pilot hole for rotary, also risks creating a shelf in the radicular dentin wall. Rotary files rarely glance over shelves or ledges and must be meticulously removed before proceeding.4 An excellent series of manual files for smooth and progressive Glidepath enlargement are the ProFile Series 29 invented by Schilder (DENTSPLY Tulsa Specialties) (Figure 15).
3. “Envelope.” If the file does not easily “follow” to the RT, stop short of maximum resistance. You now have 2 choices: force or remove. If you force, you may block or ledge. So, DO NOT FORCE or PUSH. The proper next step is to remove the file using the “envelope of motion.” The envelope will wear away restrictive dentin by withdrawing and carving to the right, or clockwise, direction. Envelope is the only motion of the 4 manual motions that removes dentin on the outstroke. The other 3 motions require that the file is moving in an apical motion in order to execute. This is a subtle motion and gives the impression that you are wasting your time because nothing is happening. But remember, endodontics is not a big job, it is a little job. The amount of tooth structure that is removed compared to coronal enamel and dentin preparations is minuscule. Endodontics is, however, a smart job. The “envelope motion” is a smart and efficient motion. Test it out yourself and experience that suddenly, effortlessly, and even miraculously the previous file “follows” deeper. You will experience a newfound freedom and control of the evolving radicular shape which, unfortunately, cannot be observed directly like all other restorative. Your unimpeded files are your eyes in endodontics. Now “follow” to the RT with your smallest file, smooth, and finish Glidepath. If you cannot “follow” to RT, you will almost always at least “follow” closer toward the RT. Envelope again and repeat until you reach RT, smooth, and finish the Glidepath.
4. “Balance.” Sometimes a file size larger than a super loose No. 10 is desired. The dentist may feel safer with a larger size or the walls may not feel as smooth as possible. If you want to have a smooth No. 15 as your Glidepath size, for example, then use balance motion. It is safe and predictable. Originally this motion was referred to as Balanced Force or the Roane Technique, named after Dr. James Roane, the first person to describe this manual motion.6 Simply put, turn the handle of the file clockwise, and then turn it counterclockwise using slight apical pressure so that the file will not “unscrew” its way out of the canal. During the clockwise motion, the file blades cut into the dentin; during the apical counterclockwise motion, the dentin is collected into the file’s flutes. This can be repeated several times as the file is “balanced” apically. The file is then turned clockwise and removed having carved a wider Glidepath. That same file is then used in a “smoothing” motion and the Glidepath is once again finished and ready for rotary shaping.
A new approach to increasing Glidepath size is mechanically vs. manually. One recent and successful method is the introduction of 3 PathFiles (DENTSPLY Tulsa Specialties) (Figure 16). When properly used, these robust and efficient rotary Glidepath files can take even further risk out of rotary shaping. As with every dental instrument, the dentist must precisely follow the manufacturer’s directions for use.

SUMMARY
The endodontic Glidepath is the secret to radicular rotary safety. This article has offered a definition of Glidepath, explained why it is important in producing optimum endodontic mechanics, and described how to prepare a Glidepath for radicular shaping. Four obstacles to Glidepath preparation have been identified along with the solution for each one. Four manual motions have been distinguished that, if used properly, will produce a safe rotary result and an endodontic experience that you truly control.