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Written by Richard Mounce, DDS Friday, 01 June 2007 00:00
Stopping 15 feet below the surface for 3 minutes—known as a safety stop—is a cardinal rule in recreational scuba diving. A safety stop is the endodontic equivalent of giving a patient local anesthetic or using a rubber dam. It is an essential component of the dive. Recently I was on a dive in Micronesia in which the guide did not have the group perform the safety stop. After I made my stop away from the group, I questioned the guide. The conversation that followed amounted to, “It works for me,” and “I’ve never had a problem.”
“It works for me” is not a suitable strategy for safety while diving, nor is it a suitable strategy for cleansing, shaping, and packing root canal systems. Empirical clinical solutions are often hopeful strategies based upon opinion without extensive clinical experience or independent, university-based research. Interestingly, endodontic products are available today that have no research of any kind in the refereed journals. These products are often justified by an “it works for me” from their creators. While endodontic treatment has one goal (the 3-dimensional cleansing, shaping, and obturation of the root canal system from the orifice of the canal to the minor constriction [MC] of the apical foramen), the means to achieve this end could not be more diverse around the globe. Some utilize cold methods of obturation; others may use carriers. Some instrument by hand; others use rotary Ni-Ti files (RNT). Such a list could go on indefinitely; as a matter of fact, it is likely that no 2 clinicians anywhere perform the procedure exactly the same way.
What follows are my suggested methods to achieve the goal of endodontic treatment, collectively based on the endodontic literature, experience, and in some measure, my failures. While some nuances may be different, these are methods that many endodontists around the world share in large measure. Presented as a numbered series of steps, this paper will review key principles that can ultimately make the process more predictable, enjoyable, and profitable for the clinician.
SERIES OF STEPS
(1) Carefully assess the patient to determine the level of personal compatibility and trust between doctor and patient. If this relationship is not ideal, then the patient should be referred. Delivering care in an environment that lacks trust and cooperation is counterproductive. Profitable and, more importantly, predictable results occur from smooth and flowing treatment. The converse is also true.
(2) Carefully assess the tooth for restorability. Endodontic treatment is meaningless if later the tooth is extracted because of a vertical fracture or because the tooth cannot be properly restored. Approximately 10% to 20% of the teeth referred to me are not restorable or need some form of periodontal treatment to make them restorable. Most often the patient has no idea that such periodontal treatment is needed at the time of his or her initial examination in my office.
(3) A comprehensive examination of the patient’s chief complaint is essential. First determining if the pain is odontogenic, and if so, which tooth is the inflamed or necrotic one (in a systematic manner) is the correct order of treatment. While a comprehensive discussion of the needed elements of such an examination is beyond the scope of this paper, at its essence, there must be incontrovertible evidence that the suspected tooth is the one causing the pain. Unless such evidence exists, ideally the patient should be referred or treatment delayed until a diagnosis can be made with certainty. Never take a patient’s word about which tooth is the problem. The patient’s chief complaint must be reproduced through objective testing.
For example, if the patient claims to have pain from chewing on tooth No. 30 and sensitivity to hot and cold, all of the teeth in the lower right side should be tested to percussion and cold (in addition to palpation, mobility, and probing, aside from the other needed diagnostic tests). Tooth No. 30 should be unusually responsive to cold (which most often will be very sharp relative to the others and most likely linger as well) and be sensitive to percussion. In summary, a conclusive diagnosis must be made before treatment is started, and it must be based on incontrovertible evidence that reproduces the patient’s chief complaint.
As a brief aside, using digital radiography is a huge help in getting the best radiographic view of the tooth’s anatomy as well as the surrounding anatomic structures. I favor DEXIS digital radiography for its ease of use, software tools, cost-effective platform, and reliability. While a diagnosis is never based on the radiograph, it can obviously be helpful to see a widened periodontal ligament or obvious apical pathology to help direct the examination. Caution is advised; the absence of any remarkable findings on a radiograph does not mean that pathology is not present. The radiograph is always secondary relative to the objective examination, and, of course, the patient’s history.
(4) The patient must give consent before treatment is started. Such consent must include (among other things) having a clear understanding of the procedure, alternatives, and risks; what other treatment ideally will be required to make the tooth restorable (periodontal procedures, for example, if applicable); and having questions answered. As a practical matter, when a tooth is crowned, if I were a general practitioner I would inform the patient of the possibility that the pulp may not respond well to the trauma of the procedure and that a given percentage of such teeth develop an irreversible pulpitis. In addition, I would always test any tooth that is going to have a crown or extensive restoration for sensation to cold before proceeding to determine the level of pulp vitality (comparing the cold test results relative to the contralateral tooth). If a tooth is nonvital or partially necrotic, then determining that the tooth needs endodontic treatment prior to providing the crown can avoid the later embarrassment of the patient who presented with no pain but now develops an irreversible pulpitis requiring violation of the new restoration. Being a prophet is always preferable to the alternative. Having recent radiographs of teeth to be crowned or bridged can, in addition to the aforementioned tests, help prevent situations where a tooth with a periapical lesion is crowned and the lesion is found after a new crown is placed. Regrettably, this happens more often than we care to admit.
(5) Anesthesia must be profound. Among other strategies, waiting long enough for anesthesia to work fully, and only injecting when the anatomic landmarks are clearly located (especially with low-er molar blocks) has been very effective, and has reduced for me the number of situations where intraosseous injections become needed. Always test the tooth to percussion and cold before beginning. If there is sensitivity of any kind, wait longer or give more solution as clinically appropriate. Starting treatment on a tooth where there is any sensitivity after anesthesia is virtually always problematic.
(6) Always use a rubber dam; it is the legal and ethical standard of care. Have the patient wear eye protection.
(7) Ideally, a surgical operating microscope (SOM) should be used during treatment. There is no substitute for the magnification, lighting, and visualization made possible through its use. I use Global surgical operating microscopes (Global Surgical). Using a SOM elevates the whole process immensely. If you can do it without a SOM, then you can do it better with a SOM. If speed matters, then one flies across the Atlantic. If comfort and speed matter, then one flies across the Atlantic in first class. Using a SOM is like flying across the Atlantic in first class. Using loupes is flying in economy
in the back row on a bumpy flight. Using the naked eye is going in an odorous fishing vessel without amenities. It can be done, but it’s much more difficult.
(8) Make an estimated working length (EWL) determination before entering the tooth to make access from the initial films. If the tooth looks about 21-mm long before starting, then it probably is. If the occlusion is reduced during access, then mentally adjust the EWL based on the amount of reduction. This EWL will become important in later determining if the electronic apex locator (EAL) is giving accurate readings.
(9) Make access as big as it needs to be. Restricted access that leaves the cervical dentinal triangle in place is unproductive at best and the precursor to a failed result at worst. Such restricted access diminishes the level of irrigation possible, places torque and cyclic fatigue forces on files unnecessarily, and ultimately leads to a greater amount of uncleaned and unfilled space within the root canal system; it also predisposes the tooth to iatrogenic events of all types. Restricted access is the leading cause of missed canals. There is a balance between opening the tooth adequately and possibly too much in coronal access. Using a SOM in access (among other uses) can go far toward directing the clinician to remove just enough tooth structure to perform treatment well, and it can minimize the chances of vertical fracture and furcal floor fracture, both catastrophic events.
(10) Visualize all orifices before attempting to enter any one canal. Look for asymmetries in the chamber. If there is a cusp, then there is a canal below it. Orifices that are not centered in the chamber are a clear sign that another canal exists, usually to the opposite side of the chamber, in line with the first orifice, under a cusp tip. Having the lighting, magnification, and visualization to locate these canals is easy if combined with proper access.
Before placing anything down a canal, take a moment to evaluate how open the existing canal is at the orifice. Is the canal open to the size of a No. 6 hand file or smaller? Is the canal visible on the radiograph? Is the canal wide open such that your largest orifice opener would slide easily down it? Does the canal bend sharply at mid root? Does the canal disappear mid root on the radiograph? A careful evaluation of the size of the canals from the orifice level and their curvature radiographically can go far toward avoiding ledging, perforations, debris blockages, broken files, etc. In addition, understanding the above anatomical complexities can guide the use of orifice openers to their greatest efficiency and function. While somewhat conservative, the safest manner with which to address all canals is to place hand files into the orifice and make certain that the canal is easily negotiable throughout its length to the MC, irrespective of the radiograph. A canal that resists a No. 6 hand file from the start can be a major clinical task with regard to achieving patency, creation of a glide path, and providing copious irrigation, among other challenges.
(11) Irrigation is copious and ideally done after every insertion of a file (as is recapitulation with a small hand file). Several irrigating solutions are used: 5.25% sodium hypochlorite (SH), 2% chlorhexidine (CHX) (Vista Dental), and SmearClear (Sybron-Endo). SH and CHX are never mixed, as doing so forms an undesirable precipitate that can be challenging to remove, especially from deeper canal levels. SH and CHX are used as antimicrobial agents, and SmearClear is used to remove the smear layer to allow the placement of a bonded obturation material, as will be described later. In an average molar case, anywhere from 90 to 150 cc of solution will be used to irrigate the tooth. Ultrasonic activation of the irrigant is possible and desirable, as is warming of the solutions. Irrigation is passive, gentle, and done using syringes with predrawn contents, with the contents clearly marked, and delivered via side venting needles. Care is always taken to avoid extrusion of irrigants beyond the MC. In the future, it is virtually certain that safer and more effective irrigants, combinations, and irrigation regimens will emerge, in addition to the long-term likelihood of economical laser energy to enhance chemical irrigation.
(12) Once a decision is made to enter the canal, such entry (with hand files or RNT) is always done passively, gently, progressively, and crown-down. Instrument the coronal third of the root entirely before proceeding to the middle third. Instrument the middle third before progressing to the apical third. Instrumenting the apical third last, after the upper two thirds, is ideal. Doing so, crown-down, is consistent with cleaner canals, less iatrogenic events, more efficient instrumentation, and simpler instrument sequencing. In practical terms, using RNT files from larger tapers to smaller, and from larger tip sizes to smaller, is inherently crown-down. I use K3 files (SybronEndo) for their durability, flexibility, tactile control, cutting ability, and fracture resistance. With K3, this recommendation will manifest as using the following sequence clinically:
After hand negotiation of a given canal third and glide path creation (the canal space is opened to at least a No. 15 hand file), the following sequence (the SybronEndo K3 Procedure Pack) is commonly employed for an average molar tooth:
(a) .10 K3 25
(b) .08 K3 25
(c) .06 K3 40
(d) .06 K3 35
(e) .06 K3 30
(f) .06 K3 25
The file insertions above are repeated until the first file reaches the EWL. Once this happens, the true working length (TWL) is determined. Electronic apex locators (EALs), combined with the small spot of moisture or hemorrhage at the tip of a paper point of an appropriate taper, are both highly accurate means to determine and confirm the TWL.
Figure 1. The TCM Endo III electric motor.
Figure 2. The ELECTROtorque TLC.
Several additional points can be made:
- For a smaller canal, .04 tapers might be utilized instead of .06 only. If a given .06-tapered K3 will not advance easily, then a .04-tapered K3 sequence can be used in its place.
- It is important to realize that not all of the files listed above may be needed. It is possible, for example, that the canal is open enough that only 3 of the 6 files listed in this sequence might be needed to allow one of the files to reach the EWL. Irrespective of how many files are needed to reach the EWL, once it happens, the clinician should take a TWL reading and then gauge the apex, as will be described. K3 comes in various tapers (.02, .04, .06, .08, .10, .12) and tip sizes (15 to 60); if clinicians want to create their own individual pack configuration, then they can do so.
Tapers can be varied by intention. For example, after the .12 and .10 No. 25 tip size orifice openers, a .06 30 can be followed by a .04 25, followed by a .06 20, and finally a .04 15. The rationale for such a sequence is that each successive file will experience less torque than its predecessor. Using a variable taper sequence is a matter of personal preference.
- Entry into vital canals is best made with a viscous EDTA gel like File-Eze (Ultradent Products). This gel can be used to keep the pulp in suspension and avoid canal blockages apically. File-Eze would continuously be applied into the chamber until the bulk of the pulp was removed from the canals. In practice, after the RNT is removed from the canal, the canal would be irrigated with either CHX or SH, recapitulation would occur, and the File-Eze reapplied.
- The sequence of files above is inherently crown-down; each successive file will be inserted further apically than the file before it.
- Power the files with an electric motor, ideally one that has auto reverse and torque control. Two excellent models are the TCM Endo III, a stand-alone corded motor (Sybron-Endo), and the ELECTRO-torque TLC (KaVo). The ELECTROtorque TLC is a three-in-one system consisting of an electric high-speed, low-speed, and endodontic motor that is attached to the dental unit. These are economical products that deliver the needed function with reliability (Figures 1 and 2).
(13) As mentioned previously, after the first RNT file reaches the EWL, an EAL confirms the TWL. I do not take an image of the file in the tooth, as a length of tooth measurement is far more susceptible to inaccuracy relative to the very accurate alternatives (EAL and bleeding point on the tip of a paper point in a patent canal). The key principle in TWL determination is that all the various methods should confirm one another, ie, the EWL should closely match the EAL reading and bleeding point determination (and radiographic length, if utilized).
(14) Instrumentation after the first determination of TWL will be undertaken to finalize the preparation. For example, if the first RNT file to reach the TWL is a .06 K3 No. 15, then at this stage it is helpful to gauge the apex. Gauging is simple. A hand K-file is taken to the TWL. The diameter of the first file that resists displacement through the MC is its diameter. This file diameter is the diameter of the MC. For example, if the MC gauges to a No. 30 hand K-file, then the canal is prepared to its final diameter. While there is no absolute proof of an ideal final prepared diameter, the endodontic literature is absolutely clear that larger final prepared apical diameters provide a cleaner canal than smaller ones. In essence, a No. 50 is cleaner than a No. 30, and a No. 40 is cleaner than a No. 20, etc.1-10 Providing an apical preparation to such a larger apical diameter is not only possible but is usually easily accomplished. It is more a matter of taking the time to do it than any inherent clinical challenges. This said, in some curved and significantly calcified roots, such apical sizing may be ill-advised, but these would be exceptional clinical cases. Achieving these larger apical diameters could be done with K3 alone or a combination of K3 and LightSpeed (Discus Dental Endodontics). K3 is available to a No. 45 in .02 taper and No. 60 in the .04 and .06 taper.
(15) After the canal is instrumented to its ideal apical size, a master cone is fit. This cone fits with apical tugback in which the cone is only binding in the apical 3 to 4 mm. The TWL is reverified an additional time with an EAL, then the canal is ready for its final obturation. I use System B obturation (SybronEndo) for its simplicity and lack of a carrier. (In some techniques a carrier is left in the tooth, which might later prove vexing to remove). In addition, I bond my obturation with Resilon technology (Resilon Research) in the form of RealSeal bonded obturation material (SybronEndo). I have bonded all my endodontic obturation since January of 2004. The material is simple, economical to use, and has been shown in the preponderance of multiple independent studies to provide a better seal than gutta-percha. While I have no inherent bias against gutta-percha, it has no ability to bond to canal walls, no ability to bond to any sealer, and is almost completely dependent on the coronal seal to achieve clinical results.11-15 RealSeal, to a statistically significant degree, diminishes microbial leakage in a coronal to apical direction. As time passes, the emerging literature is favorable to RealSeal, and its popularity is growing.
While System B does not have to be done under a SOM, it is made that much more predictable with its use, like all endodontic procedures. Obturating a 4-canal maxillary molar with System B with a delivery device such as the Elements Obturation Unit (SybronEndo) will take about 5 minutes, at most. Practice in extracted teeth can make such obturation as efficient as possible and give clinical confidence. For a step-by-step discussion of System B obturation, the reader is directed to http://oralhealthjournal.com/issues/ISarticle.asp?id=152890&story_id=23669151352&issue=07012004&PC=.
(16) Restoration of teeth coronally after endodontic treatment is a topic of significant debate: To post or not to post? Which kind of post is best? Is it necessary to post all posterior teeth? Many such questions could be asked. One fact is incontrovertible and vital to the success of endodontic treatment irrespective of whether gutta-percha or Real-Seal is used, and that is the vital importance of an early coronal seal after treatment. The endodontic literature is very clear that microbial leakage after treatment in an unsealed tooth not only happens quickly, but such leakage is a key factor in the long-term success or failure of endodontic treatment. It makes sense to place a coronal buildup at the time of treatment while the patient is still anesthetized and the rubber dam is still in place, especially under the SOM. As an aside, it does not make good clinical sense to have an endodontist place a rubber dam to do the endodontic procedure, and then later have a post or coronal buildup done without a rubber dam, with the high risk of salivary contamination. I use Core Paste (Den-Mat) for the majority of my coronal build-ups, bonded with OptiBond Solo Plus (Kerr). Under the SOM it is a relatively simple matter to remove the interproximal areas so that the restorative dentist needs to only place a finish line.
Figures 3 to 5. Clinical cases performed in the manner described using patency, copious irrigation, and recapitulation as key principles. Instrumentation with K3 and obturation with RealSeal via System B and the Elements Obturation Unit (all materials SybronEndo), delivered under the surgical operating microscope.
TWO COMMON QUESTIONS
(1) What about teeth with open apices? How do I handle those?
Unless the clinician has extensive experience with such teeth, the materials and methods of treatment, a clear understanding of the endo-dontic literature with regard to these conditions, a surgical microscope, and the time required to treat these cases, they are best referred.
(2) I use a different RNT system. How does this change what I do?
The general principles are the same; hand instrumentation first for negotiation and glide path creation is almost always desirable before RNT use. In principle, using larger tapers and tip sizes first, followed by smaller, is inherently crown-down, and if the tactile use of the files is correct (slow, gentle, and passive, minimizing engagement of the file flutes against the canal walls), then efficient use of most RNT systems irrespective of brand is ensured (Figures 3 to 5).
“It works for me” is neither a suitable dive plan nor a justification for performing endodontic therapy. A logical and literature-based means to provide nonsurgical endodontic treatment has been provided to general practitioners. The methods provided have been used extensively and honed over years of practice, and blended with the evolving endodontic literature. These are methods and principles that largely mirror a significant number of endodontists in specialty practice. I welcome your questions and feedback.
- Parris J, Wilcox L, Walton R. Effectiveness of apical clearing: histological and radiographical evaluation. J Endod. 1994;20:219-224.
- Card SJ, Sigurdsson A, Orstavik D, et al. The effectiveness of increased apical enlargement in reducing intracanal bacteria. J Endod. 2002;28:779-783.
- Rollison S, Barnett F, Stevens RH. Efficacy of bacterial removal from instrumented root canals in vitro related to instrumentation technique and size. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2002;94:366-371.
- Tan BT, Messer HH. The quality of apical canal preparation using hand and rotary instruments with specific criteria for enlargement based on initial apical file size. J Endod. 2002;28:658-664.
- Falk KW, Sedgley CM. The influence of preparation size on the mechanical efficacy of root canal irrigation in vitro. J Endod. 2005;31:742-745.
- Dalton BC, Orstavik D, Phillips C, et al. Bacterial reduction with nickel-titanium rotary instrumentation. J Endod. 1998;24:763-767.
- Siqueira JF Jr, Lima KC, Magalhaes FA, et al. Mechanical reduction of the bacterial population in the root canal by three instrumentation techniques. J Endod. 1999;25:332-335.
- Shuping GB, Orstavik D, Sigurdsson A, et al. Reduction of intracanal bacteria using nickel-titanium rotary instrumentation and various medications. J Endod. 2000;26:751-755.
- Usman N, Baumgartner JC, Marshall JG. Influence of instrument size on root canal debridement. J Endod. 2004;30:110-112.
- Ram Z. Effectiveness of root canal irrigation. Oral Surg Oral Med Oral Pathol. 1977;44:306-312.
- Barrieshi KM, Walton RE, Johnson WT, et al. Coronal leakage of mixed anaerobic bacteria after obturation and post space preparation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1997;84:310-314.
- Torabinejad M, Ung B, Kettering JD. In vitro bacterial penetration of coronally unsealed endodontically treated teeth. J Endod. 1990;16:566-569.
- Saunders WP, Saunders EM. Assessment of leakage in the restored pulp chamber of endodontically treated multirooted teeth. Int Endod J. 1990;23:28-33.
- Chailertvanitkul P, Saunders WP, Saunders EM, et al. An evaluation of microbial coronal leakage in the restored pulp chamber of root-canal treated multirooted teeth. Int Endod J. 1997;30:318-322.
- Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod J. 1995;28:12-18.
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