By Marco Versiani, D.D.S., MSc, Ph.D.
The fundamental basis to perform successful root canal treatments is the knowledge of the anatomy of teeth. A lot of research have been done on this topic since the start of the 20th century and their findings have had a noteworthy influence on clinical practice and dental education. However, the methods used in these studies usually required the partial or even full destruction of teeth, while others provided only two-dimensional views of a three-dimensional structure. Throughout the years, technological advancements in the field of digital imaging overcome these limitations by employing non-destructive high-resolution tomographic devices, named CBCT and micro-CT. While CBCT allows to evaluate the influence of ethnicity, aging, and gender on the canal morphology of large populations, micro-CT enables not only the visualization of small details in the inner structure of teeth, but also to calculate specific morphometric parameters of root canals based on hundreds of cross-sectional slices1.
In the last 10 years, because of the mentioned imaging application achievements, dental literature was flooded by an increasing number of publications on root canal anatomy. However, although all of these scientific improvements, recent CBCT studies still report a high prevalence of apical periodontitis associated to missed-untreated canals2-4, mostly in molars. In these teeth, it may be assumed that canals were left untreated not only because dentists were unable to find them, but also for being unaware about their presence. It is unbelievable that even after 107 years since Hans Moral5 reported a high frequency of a second canal in the mesiobuccal root of maxillary first molars, the so-called MB2, we keep talking about it as a variation and not as a regular anatomy. Likewise, since isthmuses were estimated to be present in approximately 70% of molars6, it means that this morphological condition is more of a rule than an exception in these teeth. Another anatomical aspects that are usually neglected is the high prevalence of 2 canals in single-rooted mandibular incisors (20-25%)7 and premolars (up to 32.7%, depending on the country)8, as well as, of C-shaped canals, merging canals, canal interconnections, and apical ramifications in maxillary second molars with fused roots9 and mandibular premolars with radicular grooves10. Finally, we must always remember that the cross-sectional canal shape is extremely variable, rarely round, and usually larger in its buccal-lingual dimension, morphological features that cannot be directly observed in conventional radiographs. Note that these are only basic anatomical aspects that every specialist or general practitioner should know before performing a root canal treatment. So, how can we explain this high prevalence of teeth with missed-untreated canals?
Throughout its history, Dentistry often developed itself based on empiricism—a theory that states that knowledge comes primarily from sensory experience—but, in the contemporary world it would not be prudent to any discipline in the health field to advance without science. It is true that the vast majority of available scientific evidences in Endodontics are not strong enough because they were mostly derived from bench studies. But it is also likely that several questions (Should we remove the smear layer? What is the ideal concentration of NaOCl? What is the optimal apical preparation size?…) will not be definitely answered in the near future because of ethical or economic issues. So, our practice must be based on the best available evidence, even if it comes from laboratorial studies. For instance, it has been demonstrated in clinics that bacteria present in a non-treated canal system of a necrotic tooth can jeopardize the treatment outcome11. It is also well-known by laboratorial data that (1) bacteria are organized within the canal space into complex communities known as biofilm, (2) the non-crystalline extracellular matrix of the biofilm provides protection of bacteria from chemical treatments, and (3) mechanical action is needed to break up the protective matrix around the biofilm and allow disinfectants to work. Concurrently, studies in extracted teeth demonstrated that our shaping protocols are unable to reach all surface area of the root canal system12, 13 and, therefore, when treating infected teeth, disinfection must be improved before filling14. This is only one example to demonstrate how to combine data from clinical studies with well-designed laboratorial research. Notwithstanding this association seems quite obvious, the large emphasis placed on technology nowadays is clouding our perception on how to understand our specialty to move it towards the future.
In Endodontics, as in other health fields, applied technology has proven itself to be a double-edged sword: on one side, it makes our practice easier and more predictable; on the other side, it brings the oversimplification of methods into a very complex environment: the root canal system. Under these circumstances, if technology is applied without following essential scientific concepts, major distortions may occur, such as the case of missed canals. More serious is what we are witnessing on social networks. Now, a good clinician is rated not by the capacity to perform a root canal treatment according to scientific principles, but by the ability to shape the canals faster than never, or to execute a treatment through a tiny hole as possible created on the crown, usually conserving more restorative materials than dental structures. It is curious to observe that an opinion posted by some of these gurus sometimes has more weight for the audience than the ones provided by years of experimental testing in the academic field. Therefore, the greatest challenge in Endodontics nowadays is not technological, but educational.
Undoubtedly, the scientific-based knowledge developed by the academy throughout the last centuries are losing space very fast for opinions shared in social networks, and the incomprehensible and boring technical language is probably one of the main causes. Endodontics must keep going on technological advancements but, as clinicians, we must also develop our ability to critically understand the interplay between the already-known complex internal morphology of teeth and the root canal treatment procedures, but based on the best evidence available. To achieve this goal, the academy must go outside its walls and be more active, not only in the professional meetings, but also in social networks, aiming to unveil pseudoscience, to filter relevant and unbiased information, and to present science in a more comprehensive and attractive way to the public. As properly stated by Carl Sagan, “Science is far from a perfect instrument of knowledge. It’s just the best we have.”15
- Versiani MA, Basrani B, Sousa-Neto MD. The root canal anatomy in permanent dentition. 1 ed. Switzerland: Springer International Publishing; 2018.
- Costa FFNP, Pacheco-Yanes J, Siqueira JF, Jr., Oliveira ACS, Gazzaneo I, Amorim CA, Santos PHB, Alves FRF. Association between missed canals and apical periodontitis. Int Endod J 2019;52:400-6.
- Karabucak B, Bunes A, Chehoud C, Kohli M, Setzer F. Prevalence of apical periodontitis in endodontically treated premolars and molars with untreated canal: a cone-beam computed tomography study. J Endod 2016;42:538-41.
- Baruwa AO, Martins JNR, Meirinhos J, Pereira B, Gouveia J, Quaresma SA, Monroe A, Ginjeira A. The influence of missed canals on the prevalence of periapical lesions in endodontically treated teeth: a cross-sectional study. J Endod 2020;46:34-9.
- Moral H. Ueber Pulpenausguesse. Dtsch Mschr Zahnheilk 1914;32:617-24.
- Pécora JD, Estrela C, Bueno MR, Porto OC, Alencar AH, Sousa-Neto MD, Estrela CR. Detection of root canal isthmuses in molars by map-reading dynamic using CBCT images. Braz Dent J 2013;24:569-74.
- Martins JNR, Marques D, Leal Silva EJN, Carames J, Mata A, Versiani MA. Influence of demographic factors on the prevalence of a second root canal in mandibular anterior teeth – a systematic review and meta-analysis of cross-sectional studies using cone beam computed tomography. Arch Oral Biol 2020;116:104749.
- Martins JNR, Marques D, Silva E, Carames J, Versiani MA. Prevalence studies on root canal anatomy using cone-beam computed tomographic imaging: a systematic review. J Endod 2019;45:372-86 e4.
- Ordinola-Zapata R, Martins JN, Bramante CM, Villas-Boas MH, Duarte MH, Versiani MA. Morphological evaluation of maxillary second molars with fused roots: a micro-CT study. Int Endod J 2017;50:1192-200.
- Boschetti E, Silva-Sousa YTC, Mazzi-Chaves JF, Leoni GB, Versiani MA, Pecora JD, Saquy PC, Sousa-Neto MD. Micro-CT evaluation of root and canal morphology of mandibular first premolars with radicular grooves. Braz Dent J 2017;28:597-603.
- Chugal NM, Clive JM, Spångberg LS. Endodontic infection: some biologic and treatment factors associated with outcome. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96:81-90.
- Peters OA, Laib A, Gohring TN, Barbakow F. Changes in root canal geometry after preparation assessed by high-resolution computed tomography. J Endod 2001;27:1-6.
- Versiani MA, Leoni GB, Steier L, De-Deus G, Tassani S, Pécora JD, Sousa-Neto MD. Micro-CT study of oval-shaped canals prepared with SAF, Reciproc, WaveOne and ProTaper Universal systems. J Endod 2013;39:1060-6.
- Siqueira JF, Jr., Alves FR, Versiani MA, Roças IN, Almeida BM, Neves MA, Sousa-Neto MD. Correlative bacteriologic and micro-computed tomographic analysis of mandibular molar mesial canals prepared by Self-adjusting File, Reciproc, and Twisted File systems. J Endod 2013;39:1044-50.
- Sagan C. The demon-haunted world: science as candle in the dark. 1 ed. New York: Random House Publishing Group; 2011.
Dr. Marco Versiani is Colonel Dental Officer of the Brazilian Military Police and Invited Researcher, Fluminense Federal University, Rio de Janeiro, Brazil.