The Endodontic Glidepath: “Secret to Rotary Safety”

[Anonymous]

GLIDEPATH TECHNIQUE
There are 4 skills that you need to know in order to produce consistent Glidepaths for safe rotary. First, find the canal. When beginning an endodontic procedure, it is useful to know the number of canals typical to a particular tooth.1 It is also useful to know the typical anatomic variations of the specific tooth you have scheduled to treat (ehuman.com/products/3d-tooth-atlas-6). When reviewing ToothAtlas teeth, the first realization is the typical root canal system anatomy of a specific tooth is not typical at all. None are the same and that is the lesson: always expect the unexpected; no 2 root canal systems are the same—root canal systems are literally like “banners in the breeze.” They are complicated and curved, their canal walls vary from smooth to rough, from wide to narrow, or from patent to clogged with pulp, necrotic debris, or calcifications. Once you know the typical number of canals for a particular tooth and you understand some of the anatomical possibilities, then magnification and illumination are essential to finding canals. Any dentist serious about endodontic treatment should be trained in the use of the operating microscope. With an aging population and therefore aging teeth with their root canal systems, normal calcific degeneration occurs and when these pulps become nonvital, the canals are smaller and more difficult to find without magnification and illumination (Figure 10).
Second, “follow” the canal to its radiographic terminus (RT). While the RT is always some distance past the physiologic terminus, the RT is the best default or home base position (Figure 11). By “following” to the RT, the clinician guarantees foraminal patency, which is prerequisite for a successful Glidepath. The technique is to clean to the RT and then shape inside using a wide variety of physiologic terminus location methods such as apex locator, paper point determination, different angle radiographs or digital images, and, finally, patient response to an endodontic file passing through the foraminal constriction where a lesion of endodontic origin exists and anesthesia is not being used or wearing off at the end of a visit.

Third, understand the 4 possible reasons (or a combination of these 4 reasons) why you may not be able to easily follow to the RT (Figure 12).3,4
1. The canal is clogged or seemingly blocked by dense collagen or necrotic debris. This is the fatal flaw of Glidepath preparation. Solution: irrigate thoroughly with sodium hypochlorite, make an abrupt apical curve on smallest file in your armamentarium (typically a size No. 6 or No. 8 file), imagine successfully reaching the RT (actually imagine seeing the file at the RT while examining the pretreatment radiograph or digital image), “follow” gently to and touch the blockage, remove the file, irrigate, re-curve the last millimeter of the file and repeat until the file moves deeper into the canal (Figure 13). Extreme restraint is required here and, at the same time, extreme intention. If you are patient and delicate enough, and if you do not put a time limit on this essential skill, I promise you that you will eventually “follow” successfully to the RT!
2. The angle of access and the angle of incidence are not the same. In other words, the file curvature and the canal curvature do not mimic each other. Solution: The key here is randomization. Rather than think “the canal goes left,” or “the canal is coming toward me,” instead simply allow the file to “follow” to the RT with little or no concern which direction it curves apically. Your only concern or outcome is to reach the RT. So, if you do not reach the RT with the first apical curve that you make, make a different curve and “follow” with that file. Then, if you do not reach the RT, make another different curve, and so on. Maybe multiple apical curves will be the answer. The guideline again is patience, restraint, and gentleness. NEVER FORCE OR PUSH! NEVER, EVER! Forcing is a natural response and must be resisted for Glidepath success. Being aware of the tendency and immediate normal reaction to push when you encounter resistance is the first step to overcoming making the “fatal flaw” worse. Relax; take your time. Once you successfully reach the RT, the rest is easy; simple mechanics. How you manage this moment in Glidepath preparation is the difference that makes the difference.
3. The diameter of the file is too wide for the canal that it is following. In other words, the file does not fit. Solution: Easy. Choose a smaller file. At no time do you know what solution will be the answer. You use all the solutions 1, 2, and 3 all at once. Be delicate. Change the curve. Go to a smaller file. You do not care what the solution is; you only care that you reach the RT.
4. The shaft of the file is too wide for the canal. In other words, the file cannot “follow” deeper into the canal because restrictive coronal dentin will not allow it. Remember, pulps not only inflame and necrose coronal-apically, they also calcify coronal-apically. Solution: Sometimes changing to a smaller file with a narrower coronal diameter will allow the file to “follow” deeper. A second method to remove restrictive dentin is to mechanically remove the restrictive dentin using Gates Glidden drills or nickel titanium rotary files short of the depth followed by the manual file. Historically, this approach has been referred to as early coronal enlargement. Progresssively tapered files (such as ProTaper Universal [DENTSLPY Tulsa Specialties]), used in a brushing motion, are particularly effective and efficient for restrictive dentin removal through the technique.5 A third method for restrictive dentin removal is the “envelope of motion” manual motion which is described below.

Seemingly, while all 4 Glidepath “following” skills are separate, they are not. Often combinations of the 4 conditions exist, requiring a combination of solutions. For example, a canal might be packed apically with necrotic debris, have restrictive dentin, and you may choose a file that is too wide. Without being delicate, removing restrictive dentin and choosing a narrower file all at the same time is a recipe for failure to follow to the RT, which is the critically essential step of a successful Glidepath.