Is a filled lateral canal - A sign of superiority?

Three-dimensional disinfection is more important than three-dimensional obturation., This letter refreshes and re-emphasizes various concepts on filling lateral canals and apical ramifications. Several questions on the importance of filling these accessory innervations if any, beneficial role of filling accessory canals on treatment outcomes if any are addressed. It is preferable to use a root canal system or a root canal complex, rather than stating with a simple terminology as a root canal. The road from the coronal orifice to the apical terminus is never straight and single. There are many accessory pathways in between and might be numerous at the apical terminus. Accessory or lateral canals are not always radiographically detectable.,

Clinically complete cleaning of these ramifications without leaving any tissue residue or infected inorganic debris is questionable. It is not possible to thoroughly clean accessory or lateral canals.5, 6, 7, 8 So, forcing radiopaque material may be a sealer or gutta-percha into these minute accessory pathways and stating it to be the superiority in completely cleaning and disinfecting these areas is inappropriate. Clinically, several questions have to address that, these apical puffs and lateral canal fill are intentional or unintentional? Are they passively filled by the obturating material or being forced into these areas? Complete filling of an accessory or lateral canals is not clinically feasible.

The term “Passive Irrigation” is employed in root canal debridement, where the mode of delivery in passive, by slowly injecting an irrigant into a canal, and the hydrodynamic effects of root canal irrigants are exerted mostly on root canal walls inducing least apical forces. Currently employed techniques for thermoplastic root canal obturation uses forces laterally and apically to fill in three dimensions. But the presently proposed “Passive root canal filling” is a hypothesized concept, where we want to emphasize on a concept of root canal obturation, where obturation materials can passively be inserted into root canal spaces with least induced apical forces, thereby preventing the excessive extrusion of root canal sealer or gutta-percha.

As stated by Dr. Barry L Musikant, “A passive obturation technique, can scrupulously avoid the introduction of stresses and maintain accurate placement of gutta-percha”. The author emphasized that trauma-free obturation is a single point technique. The author's views were in correlation with the previous literature, which states a single cone obturation technique, to be less operator dependent and less damaging to root canal dentin. Like all other techniques, the single point technique is based on the cement. To improve the single point obturation technique, a bidirectional spiral was developed by incorporating a design, which enhances the three-dimensional seal along the length by driving excess cement coronally.

Currently employed single-cone root canal obturation techniques using bio ceramic based materials in endodontics proved superiority in the clinical outcome on a retrospective analysis. So, current endodontic obturation technology should concentrate more on these passive obturation techniques.

We emphasize more on “passive irrigating strategies” but the same “passive root canal filling concept” is not being applied. From a standpoint of view, an endodontic procedure should be passive and painless starting from access cavity preparation till the obturation of canals. If these procedures fill passively the accessory pathways, they should induce minimal or no postoperative pain to the patient. Because these avenues are already opened and there is no requirement of any forcing or squeezing of material into these areas.

It is better to understand that a root canal system is like an open-ended tube, with a minute opening which might be a major terminus with multiple avenues which are way beyond our imagination and not always possible to disinfect clean and fill all these areas passively with the presently employed techniques. Before understanding the clinical scenario, it is better to re-evaluate the histological standpoints and come to the conclusion of a specific scenario. It is better to simplify the condition of the pulp as vital, inflamed, necrotic, necrotic and infected. So, at a histological standpoint, the pulpal tissue of accessory canals in inflamed cases and to some extent in infected cases is still vital. The reason being, these areas are innervated by the periodontal blood circulation. In some cases it is noted that at the exit of the lateral canal in the periodontal ligament was free from inflammation. Especially in cases, where the blood circulation of the bulkier lateral canals was intact, the bulk of pulpal tissue proximal to the main canal although, damaged by the instrumentation, irrigation, and obturation, the bulkier tissue in ramifications and lateral canals were left undisturbed and uninflamed as observed in series of histological sections.

When histological sections were observed with the filled endodontic materials in these ramifications and lateral canals containing vital tissue, the ramification was not filled with observed damaged and inflamed tissue around the filled material. So, understanding this histological standpoint it is clear that there is no use in forcing the obturating materials unnecessarily into the ramifications in cases where preoperative pulpal status is vital or inflamed. If the nature of pulp in these accessory innervations is necrotic and infected with an obvious spread of the apical infection to periodontium causing apical and lateral periodontitis, it becomes utmost important to completely clean and disinfect, all these lateral avenues, than filling these areas with an inert material. So, detection of a lateral canal and disinfection of these avenues becomes, much more important, when there is an obvious lateral lesion. This condition ultimately dictates that there are sufficient numbers of bacteria and their products are concomitantly aggressing from apical and lateral foramina causing disease.

So, finally concluding on the present topic, it is always better to understand that regardless of the preoperative pulp conditions, the tissue within ramifications and lateral canals remain unaffected by instrumentation and even by irrigation after complete chemo mechanical preparation. The simple logic being the largest diameter of these lateral canals if any present, are nearly 2 to 3 times smaller than mean diameters of the reported main apical foramen.13, 14, 15 So, clinically it is difficult or almost impossible to disinfect and clean all these lateral canals and apical ramifications with the passive irrigation strategies being followed in the present scenario. When considering the radiopaque obturation materials in a few accessory avenues, doesn't imply that one has completely cleaned the entire root canal system, which is almost an impossible task to achieve.

Future studies have to concentrate more on laser activated irrigation strategies and photodynamic therapies which have higher capacity to penetrate and disinfect into these crocked corners of root canals space. Future studies have to concentrate more on passive obturation technologies using much more biocompatible and bioactive sealing materials, rather than the present technologies which tend to squeeze materials into these accessory avenues. When we have to consider on sealed lateral canals on treatment outcomes, none of the literature till date have addressed this point of interest and still it's a debatable topic.