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Year : 2012  |  Volume : 2  |  Issue : 2  |  Page : 65-69

Incidence of two canals in extracted mandibular incisors teeth of Saudi Arabian samples

1 Dental Department #1243, King Abdulaziz Medical City, Riyadh, Saudi Arabia
2 King Saud bin Abdulaziz University, School of Dentistry, Riyadh, Saudi Arabia

Date of Web Publication6-Mar-2013

Correspondence Address:
Khalid S Al-Fouzan
President of the Saudi Endodontic Society, Associate Dean, Academic and Student Affairs, King Saud bin Abdulaziz University, School of Dentistry, Research Associate, Eng. A.B Research Chair for Growth Fators and Bone Regeneration, King Saud University, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1658-5984.108151

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Aim: The purpose of this in vitro study is to provide clinical data on the presence of the second canal in mandibular incisor teeth of Saudi Arabian Samples. Materials and Methods: Eighty extracted human mandibular incisors were collected from Saudi patients. The teeth were accessed by small round bur then placed in 5.25% sodium hypochlorite for 24 hours to dissolve the organic debris. Indian ink was injected inside the root canal systems under negative pressure. The teeth were decalcified in 5% nitric acid for three days then dehydrated in different concentrations of ethyl alcohol. Following the decalcification process, the teeth were cleared in methyl salicylate and evaluated according to Vertucci's classification. Result: Fifty six of both mandibular central and lateral incisor teeth (70%) had type I canal configuration (one main canal and one main apical foramen), while the remaining 30% of the sample (24 teeth) had a type III canal configuration (two separate canals and merged into one canal before exiting the tooth through single apical foramen). Conclusion : The incidence of two canals in mandibular incisor teeth is about one third of the examined Saudi Arabian samples with no difference between the centrals and laterals. The clinician should deal with these teeth as if they have two canals unless it is proved otherwise.

Keywords: Canal configuration, decalcification and clearing, mandibular incisors, root canal anatomy, Saudis

How to cite this article:
Al-Fouzan KS, AlManee A, Jan J, Al-Rejaie M. Incidence of two canals in extracted mandibular incisors teeth of Saudi Arabian samples. Saudi Endod J 2012;2:65-9

How to cite this URL:
Al-Fouzan KS, AlManee A, Jan J, Al-Rejaie M. Incidence of two canals in extracted mandibular incisors teeth of Saudi Arabian samples. Saudi Endod J [serial online] 2012 [cited 2023 Feb 4];2:65-9. Available from: https://www.saudiendodj.com/text.asp?2012/2/2/65/108151

  Introduction Top

Investigators have shown that the pulp canal system is complex, and canals may branch, divide and rejoin. [1],[2],[3] The presence of leakage into the root canals is the main reason for failure in endodontic therapy. [4] The leakage may occur as a result of incomplete knowledge about the anatomical variations of root canals or from leaving unreachable areas intact, or unacceptable filled during preparation. A canal is often left untreated because the dentist fails to recognize its presence either due to lake of knowledge of root canal morphology or due to lake of experience and skills to negotiate that canal. [4] The dentist must have a thorough knowledge of root canal morphology before he or she can successfully treat a tooth endodontically. To achieve a healthy response following root canal treatment, the entire root canal system must be adequately debrided and filled. Therefore, clinicians must be familiar with the various root canal configurations and their characteristic features in various racial groups. Such knowledge can aid location and negotiation of canals, as well as their subsequent management. [4]

In reviewing the literatures, one finds a divergence of opinion concerning the anatomic configuration of the pulp cavity and the incidence of two root canals of the mandibular incisors especially they are difficult to access and the second canal usually appears to hide under the cingulam. Different studies [Table 1], [5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17] have looked at the root canal morphology of mandibular incisors over the years and pointed out that the root canal types may vary according to race.
Table 1: The incidence of two canals in mandibular incisors of different studies

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No data are available on the root canal morphology of mandibular incisors in Saudi Arabian population. Therefore, the purpose of this study is to provide clinical data on the presence of the second canal in extracted mandibular incisor teeth of Saudi Arabian Samples.

  Materials and Methods Top

In this investigation, 80 freshly extracted mandibular incisors (40 central and 40 lateral) obtained from Saudi patients attending various National Guard dental clinics of Kingdom of Saudi Arabia were collected. Teeth included in this study had intact clinical crowns and fully developed apices. The age, sex and reasons for extraction were not recorded. The identification of these teeth as either mandibular central or lateral incisors was confirmed at the time of the extraction and the teeth were collected into two labeled separate containers. All teeth were placed in 5.25% sodium hypochlorite (Odex, Bleach; Spartan Co.) for 30 minutes, after which any remaining external tissue or calculus were removed by scaling. The external surface of the collected teeth was examined for developmental groove or bifurcations. Access cavities were prepared with a high-speed handpiece and pulp tissue was dissolved by immersing the teeth in 5.25% sodium hypochlorite for 24 hours followed by 20 min immersion in an ultrasonic bath. Teeth were washed under running tap water for 2 hours and dried overnight. India ink (Sanford Rotring GmbH, Hamburg, Germany) was injected into the pulp chamber with an endodontic irrigating syringe with gauge 27 needle (BU Kwang Medical Inc., Seoul, Korea). The ink was drawn through the canal system by applying negative pressure to the apical end of the tooth with the use of a central suction system. Excess ink was then removed from the surface of the tooth with gauze soaked in alcohol. The stained teeth were air dried and decalcified with 5% nitric acid (Analytical reagents 69-71%; Gainlad Chemical Co., Clwyd, UK) for 3 days. The acid solution was changed daily and the endpoint of decalcification determined by periodic radiography. The teeth were washed under running tap water overnight and then air dried. The specimens were then dehydrated in ascending concentrations of ethyl alcohol (70%, 96% and 99%) for 12 hours each. Finally, transparent specimens were obtained by immersing the dehydrated teeth in methyl salicylate solution into which teeth were stored until examined. The specimens were examined using X3 illuminated magnifying glass (Lumagny, Great wall optical product, Hong Kong) and photographed using a digital camera (Olympus, Tokyo, Japan). The canal configurations were categorized into the first four types of Vertucci's [18] classification as follows:

  • Type I: A single canal present from the pulp chamber to the apex.
  • Type II: Two separate canals leave the pulp chamber, but join to form one canal to the site of exiting.
  • Type III: One canal leaves the pulp chamber, divides into two within the root, and then merges to exit in one canal.
  • Type IV: Two separate and distinct canals are present from the pulp chamber to the apex.

  Results Top

The transparent specimens were examined using X3 illuminated magnifying glass, and the number and type of root canals were recorded. The data was summarized in [Table 2].
Table 2: Classification and percentages of mandibular incisor teeth with various canal configuration based on Vertucci's classification

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The canal configurations of mandibular central and lateral incisors that were found in this study were type I and type III according to Vertucci's classification. Of the total sample of 80 teeth, seventy percent of mandibular central and lateral incisors (28 centrals and 28 laterals) were classified as type I (one single canal is present from the pulp chamber to the apex) [Figure 1] and [Figure 2]. Thirty percent of mandibular central and lateral incisors (12 centrals and 12 laterals) were classified as type III, (one canal leaves the pulp chamber, then it divides into two within the body of the root, then the canals merges again to exit as one canal) [Figure 3] and [Figure 4]. None of the forty teeth specimens were furcated root teeth; i.e. all had one root. Moreover, all the examined specimens had only one main apical foramen.
Figure 1: Selected pictures of single canal (type I) mandibular central incisors

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Figure 2: Selected pictures of single canal (type I) mandibular lateral incisors

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Figure 3: Selected pictures of two canals (type III) mandibular central incisors showing the Indian ink inside the canals while the roots look transparent

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Figure 4: Selected pictures of two canals (type III) mandibular lateral incisors showing the Indian ink inside the canals while the roots look transparent

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  Discussion Top

Studies of the internal and external anatomy of teeth have shown that anatomical variations can occur in all groups of teeth with variable prevalence in different ethnic populations. Thus, a thorough understanding of the complexity of the root canal system is essential for understanding the principles and problems of shaping and cleaning, for determining the apical limits and dimensions of canal preparations, and for performing successful microendodontic procedures.

Careful evaluation of two or more periapical radiographs is mandatory. These angled radiographs provide much needed information about root canal morphology. Nattress et al.[19] radiographed 790 extracted mandibular incisors and premolars in order to assess the incidence of canal bifurcation in a root. Using the 'fast break' guideline that the disappearance or narrowing of a canal infers that it divides resulted in failure to diagnose one-third of these divisions from a single radiographic view. The evaluation of the root canal system is most accurate when the dentist uses the information from multiple radiographic views together with a thorough clinical exploration of the interior and exterior of the tooth.

A variety of techniques have been proposed to permit visualization of the root canal system and the effect of biomechanical procedures on its morphology. Sectioning of the roots at right angles to the long axis is of value in determining canal contour and size. [20],[21] But this technique does not permit a continuous view of the canal system. Longitudinal sectioning of the root compensates for the previous limitation by providing an intact canal surface. [22] However, only a limited amount of the canal wall can be retained, and only the more gross morphological details can be observed. Improved examination of the morphology of the canal wall is possible with the use of the scanning electron microscope which permits magnifications in excess of 2,500 and allows for a greatly detailed study of the effect of biomechanical and irrigation procedures. [20],[22] Again, the major disadvantage is the limited area available for study. Although various techniques have been used in studies evaluating canal morphology, it has been reported that the most detailed information can be obtained ex vivo by demineralization and staining. [2],[23],[24],[25] the clearing technique has considerable values in the study of root canal anatomy because it gives three-dimensional view of the pulp cavity in relation to the exterior of the tooth. In addition, the technique is simple and fast (approximately five days are required to complete the entire process). Little equipment and space are required. For this particular technique, inexpensive and less toxic chemicals were used. [26] The clearing technique of the teeth has many other applications rather than the study of root canal anatomy. It was used to assess the canal instrumentation technique, post design, microleakage and the quality of the filling. [26] Moreover, it was introduced as a teaching tool in preclinical endodontics to show the student the root canal morphology and the instrumentation procedures.

A variety of techniques to demineralized and clarify intact teeth have been reported. Many demineralizing agents have been proposed for example 5-11% nitric acid (the most commonly used agent), 20% formic acid, or 5% hydrochloric acid. The use of weak acid will avoid or reduce the shrinkage of organic tooth tissues. In the same time, many clearing agents have been proposed also (for example methyl salicylate, xylene, benzene, or eugenol) and all of those agents have the ability of making the teeth transparent.

One of the main reasons for endodontic failure of mandibular incisor teeth is the failure to locate, debride, and obturate the second canal. This study has indicated that a second canal exists in about 30% of both mandibular central and lateral incisor teeth. Moreover, all the examined specimens had only one main apical foramen. Because of that, clinician might think that treating one canal would be sufficient since the apical foramen would be sealed, but still one would see more failure in these teeth. However, one should not feel secure in treating only one canal since the second canal would become necrotic and can liberate noxious byproducts through the accessory and lateral canals into the periodontal ligament space or moreover through the insufficient apical seal of root canal filling materials. [4]

The incidence of two canals in mandibular anterior teeth has been reported by several authors to vary between 12.4% to 53% respectively. [5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17] Our results (30%) fall in almost the middle of this range. In addition, we found that there is no difference between the mandibular centrals and laterals in the incidence of two canals, which may be attributed to the sample size and the racial differences. Other factors that can contribute to differences observed in the various anatomical studies have been reported by Cleghorn et al.[27]

An important aid for locating root canals is the dental-operating microscope which was introduced into endodontics to provide enhanced lighting and visibility. It brings minute details into clear view. It enhances the dentist's ability to selectively remove dentin with great precision thereby minimizing procedural errors. Several studies have shown that it significantly increases the dentist's ability to locate and negotiate canals. [21],[28],[29]

It is humbling to be aware of the complexity of the spaces we are expected to access, shape, clean and fill. We can take comfort in knowing that even under the most difficult circumstances our current methods of root canal therapy result in an exceptionally high rate of success.

  Conclusion Top

The incidence of two canals in Saudis mandibular incisor teeth is about one third with no difference between the central and lateral incisors. A thorough knowledge of tooth morphology, careful interpretation of angled radiographs, proper access preparation, a detailed exploration of the interior of the tooth, and magnification and illumination are essential prerequisites for a successful treatment outcome.

  References Top

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29.Go¨rduysus MO, Gorduysus M, Friedman S. Operating microscope improves negotiation of second mesiobuccal canals in maxillary molars. J Endod 2001;27:683-6.  Back to cited text no. 29


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2]

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