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The Endodontic Glidepath: “Se cret to Ro ta ry Safe ty”

INTRODUCTION is to serve as a reference guide for endodon - WHAT IS A GLIDEPATH? You will do it 5,000 times in your career. tic Glidepath preparation and answer the The endodontic Glidepath is a smooth radic - Give or take a few… following questions: What is it? Why is it ular tunnel from canal orifice to physiologic The ADA estimates that most important? How do you predictably prepare terminus (foraminal constriction). Its mini - treat an average of 2 endodontic teeth per the Glidepath? mal size should be a “super loose No. 10” week. If we assume there are at least 2 canals endondontic file. The Glidepath must be dis - per tooth, 47 treatment weeks per year for STARTING WITH THE ANSWER covered if already present in the endodontic 25 years, then most dentists will attempt The purpose of endodontics is to prevent anatomy or prepared if it is not present. The John D. West, approximately 5,000 Glidepaths in their or heal lesions of endodontic origin. 1 In Glidepath can be short or long, narrow or DDS, MSD career: 2 root canals per week x 2 canals per order to achieve this purpose, the root wide, essentially straight or curved (Figure 2). tooth x 47 weeks x 25 years = approximately canal system must be successfully obturat - 5,000 Glidepath attempts. ed. In order to be obturated, the WHY IS THE ENDODONTIC GLIDEPATH The amazing fact is that the subject of system has to be successfully 3-dimension - IMPORTANT? Glidepath has no formal training in the ally (3-D) cleaned and rotary shaped. In First, without the endodontic Glidepath, the endodontic curricula of most dental order to be 3-D cleaned and rotary shaped, rationale of endodontics cannot be achieved. schools. In fact, a PubMed Central search of a Glidepath has to be successfully pre - The rationale states that “any endodontically Glidepath and endodontics reveals 300 ref - pared (Figure 1). And so the Glidepath is diseased tooth can be predictably saved if the erences. However, none of them actually the answer. It is the starting point of radic - root canal system can be nonsurgically or describe how to prepare a Glidepath. Most of ular preparations. Without it, cleaning surgically sealed, the tooth is periodontally the references say something like, “Of and shaping become unpredictable or sound or can be made so, and the tooth is course you must first make a Glidepath.” impossible because there is no guide for restorable.” 1 A nonsurgical seal requires first That’s all. And so the purpose of this article endodontic mechanics. the creation of a radicular path that can be cleaned of viable and nonviable bacteria, vital 1. What size hand file do you prefer for your Glide Path? (Choose one) and nonvital tissue,

A. Size #10______biofilm, and smear layer; B. Size #15______C. Size #20______then shaped to a continu - D. Larger______ously tapering funnel that 2. Do you use straight manual files or do you curve them? (Choose one) can be predictably and eas -

A. Straight______ily obturated. B. Curved______Second, the Glidepath 3. Do you “go to length immediately” if you can or do you “do early coronal enlargement” is necessary for quality first? control. Sustainable excel - A. Immediately if I can_____ B. Early coronal enlargement______lent endodontic obtura - Figure 1. Glidepath is key to Rotary Shaping. 4. When making the Glide Path, what is your preferred irrigation solution? (Choose one) tions are not possible Pretreatment image (left) shows apparent apical calci - without it. fication. Post-treatment image (right) reveals proper A. Sodium hypochlorite______B. EDTA______apical shaping and obuturation made possible by suc - C. Viscous chelator such as ProLube, Glide, or RC Prep______cessful Glidepath preparation. D. Combination of the above______HOW DOES THE

5. How do you determine your Glide Path length? (Choose one) PREDICTABLY PRE - A. Apex locator______B. Radiographic terminus______PARE THE GLIDEPATH? C. Both of the above______In order to answer this

6. When making the Glide Path, what hand motion(s) do you use? i.e.: “watch/wind,” question, I first surveyed “push/pull,” or other. the American Association of Endodontists (AAE) 7. When blocked, what do you do next? and reported my findings

at the AAE annual scien -

8. When you first notice a shelf starting, what do you do next? tific meeting in San Diego Figure 2. 2 Glidepaths occur in multiple widths, lengths, on April 16, 2010. The and curvatures. They can be long or short, wide or nar - title of my presentation row, curved or more curved. Root canal system anato - 9. If you were to design the ideal Glide Path file(S), what would you want as your most desired features or characteristics? Please be specific. (Optional) was “The Magic of Mas- my is often tortuous and in multiple planes not observed in 2-dimensional images. Glidepaths must tering the Glidepath: ultimately “follow” and replicate the original canal path What Every Endodontist Figure 3. in order to preserve the position of nature’s portal of Sample of Glidepath survey letter to endodontists. Answers to Nos. continued on page 88 exit locations. 1 through 6 are presented in Figures 4 to 9.

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The Endodontic Glidepath... Hand File Size Preference Straight or Curved File Preference Go to Length Immediately or Early continued from page 86 Coronal Enlargement

3% Size No. 10 Should Know .” I asked the following 6 Straight Immediately Size No. 15 questions (Figure 3). The survey 16% Curved Early Coronal 18% Size No. 20 Enlargement results speak for themselves. Larger 43% 1. What size hand file do you pre - 45% fer for your Glidepath (Figure 4)? 2. Do you use straight manual files 57% or do you curve them (Figure 5)? 84% 34% 3. Do you “go to length immedi - ately” or do you do “early coronal enlargement” (Figure 6)? Figure 4. Figure 5. Figure 6. 4. When making the Glidepath, Hand File Size Preference. More Straight or Curved File Preference. Go to Length Immediately or Early than one-half of endodontists prefer a rotary The only valid time to use a straight file is slid - Coronal Enlargement. Slightly more endodon - what is your preferred irrigating solu - Glidepath file size No. 15 or larger. As ing into the orifice where the angle of inci - tists prefer early coronal enlargement, primarily tion (Figure 7)? described in this article, the author prefers, dence is greater than the angle of access. due to the presence of restrictive dentin which 5. How do you determine your instead, a “super loose No. 10.” restricts finesse and mastery of the first Glidepath length (Figure 8)? Glidepath file. 6. When making the Glidepath, Irrigation Solution Preference Determination of Hand Motion Preference what hand motion do you use (ie, Glidepath Length Sodium Watch/Wind “watch/wind,” “push/pull,” or other) Hypochorite Apex Locator Push/Pull (Figure 9)? EDTA Radiographic 9% Both Viscous Terminus 32% Chelator 32% Both Other GLIDEPATH TECHNIQUE Combination There are 4 skills that you need to know 39% 23% in order to produce consistent Glide- 55% 58% paths for safe rotary. First, find the canal. When beginning an endodontic 6% 13% 10% procedure, it is useful to know the num - 23% ber of canals typical to a particular 1 tooth. It is also useful to know the typ - Figure 7. Figure 8. Figure 9. Irrigation Solution Preference. Determination of Glidepath Length. Hand Motion Preference. Most ical anatomic variations of the specific Sodium hypochlorite and a viscous chelator (or The apex locator, or a combination of apex endodontists prefer “watch/wind.” Only 9% tooth you have scheduled to treat (ehu - a combination of the 2) enable digestion of locator and radiographic terminus, is the clini - chose “other.” This article describes the critical man.com/products/3d-tooth-atlas-6). necrotic pulp and the ability to emulsify vital cian’s choice. Canal length accuracy is excel - distinctions of the manual motions of pulp. lent when both methods of length determina - Glidepath preparation. These 4 motions make When reviewing ToothAtlas teeth, the tion validate each other. The important thing to endodontic files efficient when the dentist first realization is the typical root canal remember is that the length is dynamic and learns how, when, and why to use what system anatomy of a specific tooth is not becomes shorter, especially in the early stages motion. Glidepath demands that the dentist of rotary shaping, due to canal shortening. “thinks” and is “deeply present,” resisting all typical at all. None are the same and that distractions. is the lesson: always expect the unexpect - ed ; no 2 root canal systems are the out magnification and illumination Third, understand the 4 possible words, the file curvature and the canal same—root canal systems are literally (Figure 10). reasons (or a combination of these 4 curvature do not mimic each other. like “banners in the breeze.” They are Second, “ follow ” the canal to its radi - reasons) why you may not be able to Solution : The key here is randomization. complicated and curved, their canal ographic terminus (RT). While the RT is easily follow to the RT (Figure 12). 3,4 Rather than think “the canal goes left,” walls vary from smooth to rough, from always some distance past the physio - 1. The canal is clogged or seemingly or “the canal is coming toward me,” wide to narrow, or from patent to logic terminus, the RT is the best default blocked by dense collagen or necrotic instead simply allow the file to “follow” clogged with pulp, necrotic debris, or or home base position (Figure 11). By debris . This is the fatal flaw of Glide- to the RT with little or no concern path preparation. Solution : irrigate which direction it curves apically. Your thoroughly with sodium hypochlorite, only concern or outcome is to reach the Rather than think “the canal goes left,” or “the canal is coming make an abrupt apical curve on small - RT. So, if you do not reach the RT with toward me,” instead simply allow the file to “follow” to the RT est file in your armamentarium (typi - the first apical curve that you make, cally a size No. 6 or No. 8 file), imagine make a different curve and “follow” with little or no concern which direction it curves apically. successfully reaching the RT (actually with that file. Then, if you do not reach imagine seeing the file at the RT while the RT, make another different curve, examining the pretreatment radi - and so on. Maybe multiple apical calcifications. Once you know the typi - “following” to the RT, the clinician guar - ograph or digital image), “follow” gen - curves will be the answer. The guide - cal number of canals for a particular antees foraminal patency, which is pre - tly to and touch the blockage, remove line again is patience, restraint, and tooth and you understand some of the requisite for a successful Glidepath. The the file, irrigate, re-curve the last mil - gentleness. NEVER FORCE OR PUSH! anatomical possibilities, then magnifi - technique is to clean to the RT and then limeter of the file and repeat until the NEVER, EVER! Forcing is a natural cation and illumination are essential to shape inside using a wide variety of phys - file moves deeper into the canal (Fig- response and must be resisted for Glide- finding canals. Any dentist serious iologic terminus location methods such ure 13). Extreme restraint is required path success. Being aware of the ten - about endodontic treatment should be as apex locator, paper point determina - here and, at the same time, extreme dency and immediate normal reaction trained in the use of the operating tion, different angle radiographs or digi - intention. If you are patient and deli - to push when you encounter resistance . With an aging population tal images, and, finally, patient response cate enough, and if you do not put a is the first step to overcoming making and therefore aging teeth with their to an endodontic file passing through time limit on this essential skill, I the “fatal flaw” worse. Relax; take your root canal systems, normal calcific the foraminal constriction where a promise you that you will eventually time. Once you successfully reach the degeneration occurs and when these lesion of endodontic origin exists and “follow” successfully to the RT! RT, the rest is easy; simple mechanics. pulps become nonvital, the canals are anesthesia is not being used or wearing 2. The angle of access and the angle of How you manage this moment in smaller and more difficult to find with - off at the end of a visit. incidence are not the same . In other continued on page 90

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The Endodontic Glidepath... continued from page 88

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 Figure 11. Physiologic Terminus may actually not care what the solution is; you only Figure 10. Severely calcified canal (left) can be successfully “followed” using microscope and have different lengths. The walls of the canal care that you reach the RT. color differentiations. Note canal patency (right) did not occur until a few millimeters from the on the left are the same, while the walls of the 4. The shaft of the file is too wide for the canal terminus and yet the procedure was entirely safe and minimal tooth structure was removed. canal on the right have a longer one and a canal . In other words, the file cannot shorter one. Canal length determination is not an exact science; it is an art form. What the “follow” deeper into the canal because Solution : Sometimes changing to a remove the restrictive dentin using rationale of endodontics requires is the entire restrictive coronal dentin will not smaller file with a narrower coronal Gates Glidden drills or nickel titanium length of the root canal system be cleaned and allow it. Remember, pulps not only diameter will allow the file to “follow” rotary files short of the depth followed shaped. Glidepath is perquisite to this mechan - ical objective. inflame and necrose coronal-apically, deeper. A second method to remove by the manual file. Historically, this they also calcify coronal-apically. restrictive dentin is to mechanically approach has been referred to as early

Figure 12. Four reasons a file will not “follow” to its terminus: (1) Canal is blocked (2) File curvature does not replicate canal curvature (3) Diameter of file is too wide at its tip (4) Diameter of file is too wide in its shaft. (Often, a combination of reasons one to 4, or all 4 are the situation.) coronal enlargement. Progresssively tapered files (such as ProTaper Uni- versal [DENTSLPY Tulsa Specialties]), used in a brushing motion, are particu - larly effective and efficient for restric - tive dentin removal through the tech - nique. 5 A third method for restrictive dentin removal is the “envelope of mo- tion” manual motion which is de- scribed below. Seemingly, while all 4 Glidepath “following” skills are separate, they are not . Often combinations of the 4 conditions exist, requiring a combina - tion of solutions. For example, a canal might be packed apically with necrot - ic debris, have restrictive dentin, and you may choose a file that is too wide. Without being delicate, removing restrictive dentin and choosing a nar - rower 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. 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 thorough - ly 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 hypo- chlorite using EndoActivator (DENTSPLY Tulsa Specialties). Then dense ori - fice dentin will be removed or softened, and small files can penetrate easily and the “fol - lowing” motion can begin. Take the smallest file that fits the canal easily, and slightly precurve the apical a few mil - limeters using metal cotton pliers. If you are using a mi- croscope, 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

Four manual motions have been distinguished that, if used properly, will produce a safe rotary result.... 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 bind - ing against 2 or more walls, then wiggle the handle left and right without any up or 92 ENDODONTICS

Figure 13. Figure 14. “Follow” files are more effective when curved. First squeeze cotton pliers against file Glidepath “following” requires optimum tactile sense. Loose gloves do not enable the shaft at right angles and sweep the cotton pliers toward the tip (left). The resulting file (right) has dentist to feel the file handle (left). Gloves must fit tight so that the balls of the fingers together a gentle and continuous curve to and through its tip. allow the finest possible touch and delicacy (right). down motion. This simple, safe nuance theoretically bigger pilot hole for rotary, (DENTSPLY Tulsa Specialties) (Figure lope of motion.” The envelope will will wear away the small amount of also risks creating a shelf in the radicu - 15). wear away restrictive dentin by with - restrictive dentin and free the file for lar dentin wall. Rotary files rarely 3. “Envelope.” If the file does not drawing and carving to the right, or the smoothing motion. The minimal glance over shelves or ledges and must easily “follow” to the RT, stop short of clockwise, direction. Envelope is the Glidepath file size for safe rotary shap - be meticulously removed before pro - maximum resistance. You now have 2 only motion of the 4 manual motions ing is a loose No. 10 file. While many ceeding. 4 An excellent series of manual choices: force or remove. If you force, that removes dentin on the outstroke. endodontists prefer a larger file (55%, as files for smooth and progressive you may block or ledge. So, DO NOT The other 3 motions require that the noted in my spring AAE 2010 survey), Glidepath enlargement are the ProFile FORCE or PUSH . The proper next step file is moving in an apical motion in every increase in size while making a Series 29 invented by Schilder is to remove the file using the “enve - order to execute. This is a subtle motion and gives the impression that you are wasting your time because nothing is happening. But remember, endodon - tics 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, effort - lessly, and even miraculously the previ - ous file “follows” deeper. You will expe - rience 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 endo- dontics. 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 counter - clockwise using slight apical pressure so that the file will not “unscrew” its way out of the canal. During the clock - wise motion, the file blades cut into the dentin; during the apical counterclock - wise motion, the dentin is collected into the file’s flutes. This can be repeat - 93 ENDODONTICS

Canal System” in Cohen and Burns’ 1994 and PathFiles for Mechanical GlidePath 1998 Pathways of the Pulp . He recently authored “Endodontic Predictability” in Dr. Michael Cohen’s 2008 Quintessence text Interdisciplinary Treat- ment Planning: Principles, Design, Implementa- tion . He is a thought leader for Kodak Digital Den- tal Systems and serves on the editorial advisory boards for The Journal of Advanced Esthetics and Interdisciplinary , The Journal of Es- thetic and , Practical Proce- dures and Aesthetic Dentistry , and The Journal of Microscope Enhanced Dentistry . He can be reached at (800) 900-7668 or at john - [email protected].

Figure 16. Figure 15. New PathFile rotary Glidepath files (DENTSPLY Tulsa Specialties). These robust files, Watch for 2 more articles on the ProFile Series 29 files (DENTSPLY when used properly, can prepare a Glidepath that is safe and precise. While a manual Glidepath is topic of Glidepath by Dr. West in Tulsa Specialties). These files offer the finest still recommended, the PathFile is an excellent way to increase rotary shaping safety. manual transition between Glidepath files future issues of Dentistry Today : because of their constant and appropriate size Pathways of the Pulp . 7th ed. St. Louis, MO: endodontics at the Boston University Henry M. "Manual Versus Mechanical increases. Mosby Year-Book; 1998:203-257. Goldman School of Dental Medicine in 1975. He has presented more than 400 days of CE inter - Glidepath: When and ed several times as the file is “balanced” nationally while maintaining a private practice in How Do You Do What?” apically. The file is then turned clock - Dr. West is the founder and director of the Center Tacoma, Wash. He co-authored “Obturation of and “Implementing the the Radicular Space” with Dr. John Ingle in Ingle’s wise and removed having carved a for Endodontics. He received his DDS from the Endodontic Glidepath: University of Washington in 1971 and his MSD in 1994 and 2002 editions of Endodontics and was wider Glidepath. That same file is then senior author of “Cleaning and Shaping the Root What Are Your Action Steps?” 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 Special- ties) (Figure 16). When properly used, these robust and efficient rotary Glidepath files can take even further risk out of rotary shaping. As with every , the dentist must precisely follow the manufac - turer’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 pro - ducing optimum endodontic mechan - ics, 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 experi - ence that you truly control. !

References 1. West JD. Endodontic predictability—“Restore or remove: how do I choose?” In: Cohen M, ed. Interdisciplinary Treatment Planning: Principles, Design, Implementation . Chicago, IL: Quintes- sence Publishing Co; 2008:123-164. 2. West J. The Magic of Mastering the Glidepath: What Every Endodontist Should Know. Paper presented at: American Association of Endo- dontists Annual Session; April 16, 2010; San Diego, CA. 3. West J. Endodontic update 2006. J Esthet Restor Dent . 2006;18:280-300. 4. West JD. Perforations, blocks, ledges, and trans - portations: overcoming barriers to endodontic finishing. Dent Today . 2005;24:68-73. 5. West J. Endodontic brushing: the secret to mas - tering rotary safety. Dental Economics . August 2010. In Press. 6. West J, Roane J. Cleaning and shaping of the root canal system. In: Cohen S, Burns RC.