If you were doing a root canal for your mother, would you want her entire root canal system obturated to the radiographic apex, including all lateral canals, or would you want a shorter filling without 3-dimensional treatment? Asked another way (with phrases coined by Dr. Steve Buchanan), are you a “pulp lover” or an “apical barbarian?” A discussion of where to terminate root canal fillings and how to obturate to this point is directly related to the management and importance of lateral canals. The two are inextricably interwoven. Addressing the issue of exactly where to terminate root canal fillings is beyond the scope of this article, but a discussion of the importance of cleansing and obturating lateral canal anatomy serves to highlight the rather profound differences of opinion that exist in endodontic treatment and obturation philosophies.
Endodontists have debated for years whether lateral canals are clinically significant and have argued the best termination point for root canal fillings. Some would argue (correctly) that there is not a longitudinal study that conclusively proves that warm vertical obturation of all canal anatomy and lateral canals improves endodontic success. These practitioners generally fall into the cold lateral condensation group, which likes to instrument and fill somewhat short of the apical foramen. This camp is known affectionately as the “pulp lovers.” They would like to obturate on average 0.5 to 1.5 mm short of the radiographic apex.
In contrast, warm vertical advocates believe that every bit of canal anatomy is important and should usually be both treated and obturated to the radiographic apex (Figures 1 and 2). They would argue that failure can occur from leaving bacteria and necrotic pulp debris inside the tooth (at either the apical foramen or lateral canal), which might later escape into the bone and cause failure. In addition, they would suggest that leaving any canal space unfilled would leave a void into which tissue fluid could become stagnant and break down, thus perpetuating failure. Because this group wants to obtain and maintain apical patency of the canal by making sure small K files (sizes 6, 8, and 10) pass easily through the foramen to prevent ledging and transportation, they might be considered the “apical barbarians.”
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| Figures 1 and 2. These teeth were treated to the radiographic terminus, and patency has clearly been maintained. | |
I admit to being an apical barbarian. Estimates of the numbers of teeth with lateral canals and their locations vary widely, but conservatively, lateral canals have been reported to be present 17% of the time in the apical third, 8.8% in the middle third, and 1.6% in the coronal third of teeth.1 I believe that removal of all pulpal contents is important because, intuitively, the more pulp that is taken from the tooth, the greater the chance for healing to occur. Conversely, the more pulpal debris left in the tooth (as in uncleaned lateral canals and untreated apical-third tissue), the greater the chance of failure. While this is my opinion, it is an opinion shared by a large number of endodontists and general dentists across the world. Warm gutta-percha filling techniques address the need to obturate lateral canals by expressing gutta-percha and sealer into all ramifications of the canal system, including lateral canals. The System B Heat Source (SybronEndo) is an excellent instrument to help provide such a warm vertical method of obturation, without leaving behind a carrier that might later prove difficult to remove.
Strong evidence exists that pulpal disease (in addition to vertical root fractures) may adversely affect the periodontium, aside from solely producing odontogenic pain, and conversely, that periodontal disease may also negatively affect the dental pulp. Accessory canals in the furcal area of multirooted teeth have been reported to be found 23% to 76% of the time.2,3 The relationship between these furcal (lateral) canals and periodontal disease has not been conclusively proven, but these canals have the potential to provide a path for bacteria, toxins, and medicaments to move between the pulp and the surrounding furcal bone and periodontium. Intuitively, if pulpal disease can affect the periodontium via furcal canals, then it would seem logical that such communication along other portals of exit would also be harmful and render worthy the removal of the irritant such pulp represents.
EDUCATIONAL POINTS
I doubt that the debate over the significance of lateral canals will be conclusively settled anytime soon, but there are several important educational points to be taken from this debate:
(1) If one’s obturation technique is not picking up lateral canals and producing sealer puffs, these portals of exit are being blocked by canal debris (including the smear layer) generated during instrumentation. In re-treatment, this underscores the importance of removing (via wicking chloroform from the canal with paper points) all the gutta-percha from the root canal system. Gutta-percha not removed in re-treatment can block subsequent cleansing of lateral canals with sodium hypochlorite. Necrotic debris may remain in these blocked lateral canals and possibly cause failure.
(2) Sealer and gutta-percha are mixed together in sealer puffs. These materials are well tolerated by the body. Initially, such a tooth may be slightly sensitive, but that should pass quickly (a day or two). As the gutta-percha and sealer are compacted apically, the remaining contents of the lateral canal (necrotic debris and bacteria) are pushed into the bone, where the immune system can digest these toxins. A transitory inflammation (manifested mainly as percussion sensitivity) may ensue that will be self-limiting.
(3) Inherent in the cleansing of all inaccessible canal anatomy, including lateral canals, is the importance of proper irrigation with sodium hypochlorite; 30 minutes of soaking the tooth after instrumentation is ideal (changing the solution every 5 minutes)(Figure 3). Sodium hypochlorite can be delivered warm, activated with an ultrasonic tip or simply exchanged as above. I prefer SP ultrasonic tips (SybronEndo) for such ultrasonic irrigant activation (Figure 4).
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| Figure 3. The digestive action of sodium hypochlorite combined with the maintenance of patency and an obturation technique which will compact gutta-percha into all the ramifications of the canal system is demonstrated in this clinical result. | Figure 4. The SP Ultrasonic tips (SybronEndo, Orange, Calif). |
(4) Finally, creating a proper shape into which gutta-percha can be compacted is crucial to the obturation of lateral canals. To summarize, if canal preparation and cone fit are ideal, warm gutta-percha obturation will move a heat-softened mass of gutta-percha apically and laterally into the narrowing cross-sectional diameters of the entire canal system, including lateral canals. I use the K3 rotary nickel titanium file (SybronEndo) to safely and predictably create the shapes needed to facilitate warm vertical technique.
(5) Dentists routinely examine periapical radiographs in the apical region only. Careful examination of multiple, variously angled preoperative films, when examined along the entire length of the attachment apparatus, will demonstrate many lateral root lesions of pulpal origin as lesions form opposite the portals of exit of lateral canals.
CONCLUSION
The next time you have your mom in the chair for a root canal, consider carefully whether her child is a “pulp lover” or an “apical barbarian.” Thinking through the rationale for which camp you belong to will benefit all your patients, including mom.
References
1. De Deus QD. Frequency, location, and direction of the lateral, secondary, and accessory canals. J Endod. 1975;1:361-366.
2. Kirkham DB. The location and incidence of accessory pulpal canals in periodontal pockets. J Am Dent Assoc. 1975;91:353-356.
3. Burch JG, Hulen S. A study of the presence of accessory foramina and the topography of molar furcations. Oral Surg Oral Med Oral Pathol. 1974;38:451-455.
Dr. Mounce is in private endodontic practice in Portland, Ore. He lectures internationally and has written numerous articles for various publications, including Dentistry Today and the Journal of Endodontics. He can be reached at (503) 231-1111 or lineker@aol.com.
