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ORIGINAL ARTICLE
Year : 2005  |  Volume : 23  |  Issue : 1  |  Page : 7-12
 

A study of root canal morphology of human primary molars using computerised tomography: An in vitro study


Department of Pedodontics and Preventive Dentistry, Ragas Dental College and Hospital, Chennai, India

Correspondence Address:
Zoremchhingi
Department of Pedodontics and Preventive Dentistry, Ragas Dental College and Hospital, Chennai
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-4388.16019

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   Abstract 

Knowledge of the size, morphology and variation of the root canals of primary teeth are useful in visualizing the pulp cavity during treatment. This study was carried out to investigate the applicability of Computed Tomography in studying the root canal morphology of the primary molars. A total of 60 primary molars.without any macroscopic root resorption were collected and divided into four groups. The samples were arranged in wax block and then scanned for evaluation in the CT Scanner both in axial and coronal plane. The results obtained from the scanned images were statistically analyzed to know the frequency, mean and standard deviation for all the groups. The images showed the complexity of the root canals of the primary molars and also several capabilities of the CT Scan in advance Endodontic research in primary teeth were observed.


Keywords: Computed Tomography, Primary molars, Root canal morphology


How to cite this article:
Zoremchhingi, Joseph T, Varma B, Mungara J. A study of root canal morphology of human primary molars using computerised tomography: An in vitro study. J Indian Soc Pedod Prev Dent 2005;23:7-12

How to cite this URL:
Zoremchhingi, Joseph T, Varma B, Mungara J. A study of root canal morphology of human primary molars using computerised tomography: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2005 [cited 2017 Apr 30];23:7-12. Available from: http://www.jisppd.com/text.asp?2005/23/1/7/16019



   Introduction Top


Knowledge of the size, morphology and variation of the root canals of primary teeth are useful in visualizing the pulp cavity during treatment. As primary teeth exhibit morphologic differences from the permanent teeth both in size and in general external and internal design, a thorough knowledge of the root canal systems of the primary teeth aids in their successful treatment.

Endodontics involves cleaning, shaping and obturation of the root canal system. To improve success in endodontics, each of these steps should be evaluated throughout treatment to determine the effects of each stage of therapy. Work by many researchers has added understanding of the intricacies of the root canals.[1-4] To gather this knowledge, different techniques were used which either destroyed or altered the tooth structure, thus precluding further studies on the same teeth.

The tooth is composed of unique tissues with distinct radiographic densities and it lends itself to evaluation by tomographic techniques. Computed Tomography data seemed to offer significant advances in the ability to reconstruct with optimum detail the tissues of the tooth before and after instrumentation and obturation; also remain fully retrievable for future evaluations.[5]

Literature revealed very few studies on root canal morphology of the primary teeth and so far no studies had been done using a Computed Tomograph. So, the aim of this study was to study the applicability of Computed Tomography in studying the root canal morphology in the following parameters:

  • Number of roots;
  • Angulation of the roots;
  • Number of the root canals;
  • Diameter of the root canals;





   Materials and Methods Top


Armamentarium and Material used

1. Airotor handpiece

2. 557 carbide burs

3. No. 10 broaches

4. 5.25% sodium hypochlorite solution

5. Paper points

6. Pink wax

7. 10% formalin

8. Light speed plus CT Scanner (G.E Medical Systems, Milwaukee, USA)

Specimen Tooth Selection

Sixty extracted primary molars were collected and divided into 4 groups:

  • Group I - Mandibular first molars-15
  • Group II - Mandibular second molars-15
  • Group III - Maxillary first molars-15
  • Group IV - Maxillary second molars-15
The teeth were selected randomly. The criteria for selection was to confirm the teeth removed were intact with completely formed root apices, and without any macroscopic root resorption. The teeth were stored in 10% formalin solution.

Specimen Preparation

The teeth were then cleaned with ultrasonic scaler and access cavity prepared on the Occlusal surfaces with 557 carbide bur. No. 10 broach was used gently and advanced to the apical foramen to ensure its patency. Canals were irrigated with 5.25% sodium hypochlorite solution, then dried with paper points and the access cavity was filled with sticky wax.

Arrangement of Samples for Scanning Procedure

Pink wax was liquefied and poured in an aluminium mould and the teeth were mounted after determining the various aspects of the tooth i.e., Buccal, lingual, mesial and distal, so as to maintain uniformity in the samples. Each root was marked with a marker pen. Also care was taken to ensure that the apices of each roots of the teeth were in single plane.

Imaging System

The mounted teeth were then scanned in the CT Scanner in axial and coronal plane.

  • CT Acquisition was as follows:
  • Constant thickness- 1.25
  • Constant spiral or table speed- 0.75
  • KVP-120
  • MAS- 200


Subsequently, Volume rendering and Multiple planar volume reconstruction (MPVR) for root canal measurement were done using Advantage Windows Workstation (GE System) Image Analysis.

The length and angulations of the roots were measured by taking the greatest area of constriction as a cervical line, and the midpoint was chosen by a line through the cervical line divided by 2 and drawing a line perpendicular to the cervical lines, then rotating the MPVR in axial plane.

The diameter of the root canals was measured at the greatest diameter from the cross section of the roots irrespective of the various aspects of the canal.

Statistical Analysis

Descriptive statistics was used to find out the frequency, mean, standard deviation and range for all the four groups.




   Results Top


The following observations were made after scanning number of roots.

Table 1 represents the number of roots in all the four groups. In group I, all the samples had 2 roots i.e. 1 mesial and 1 distal, whereas in Group II, 2 of the samples there were 3 roots i.e. 2 mesial roots and 1 distal root. In Group III (Table 1b), in 8 of the samples, both distobuccal and palatal roots were fused and in 7 of the samples, all the three roots were separated. In Group IV, in all the samples the three roots were well differentiated.

Number of canals

Table 2 shows the number of canals in all the groups. In Group I, out of 15 samples only one sample had one canal in the mesial root (6.67%), and 14 samples had 2 canals (93.33%). In the distal root, six samples had one canal (40%) and nine of the samples had two canals (60%).

In Group II, 2 canals were seen in the mesial root in all the samples whereas in the distal root 3 canals were seen in one of the samples; 2 canals in 8 of the samples (53.3%), and 1 canal in 6 of the samples (40%).

In Group III, seven of the samples had three roots, which were separated; in all the samples both the distobuccal and palatal roots had one canal each. In one of the samples the mesial root had two canals and the rest of the samples had 1 canal. In eight of the samples, both the distobuccal and palatal roots were fused and in all the samples two canals were seen. i.e. 1 disto buccal canal and 1 palatal canal.

In Group IV out of 15 samples, in the mesiobuccal root- 1 canal was seen in 7 (46.6%) and 2 canals were seen in 8 (53.3%) of the samples. In the distobuccal root, 1 canal was seen in eleven (73.3%) and two canals in four (26.6%) of the samples respectively. In the palatal root, 9 (60%) of the samples had 1 canal and 6 (40%) of the samples had 2 canals. There were no fused distobuccal and palatal roots in group IV.

Diameter of the canals

As can be inferred from Table 3, in group I, maximum diameter in each thirds of the root was seen in the distal canal which had a mean canal diameter of I.imm, 0.83 mm and 0.51 mm in the cervical, middle and apical thirds of the root respectively. The minimum diameter was seen in the mesiolingual canal (cervical third - 0.57 mm, middle third -0.40 mm and apical third - 0.30 mm). Similarly in Group II, maximum diameters of the canals were seen in the distal root (cervical third -1.6 mm, middle third - 1.2 mm and apical third - 1.0 mm) and minimum diameter in the mesiolingual root (cervical third - 0.73 mm, middle third -0.55 mm and apical third - 0.4 mm).

In group III and IV, maximum diameter of the canals were seen in the palatal canals -

  • Group III - (cervical third - 1.0 mm, middle third - 0.85 mm and apical third - 0.78 mm).
  • Group IV- (cervical third - 1.3 mm, middle third - 1.02 mm and apical third - 0.81 mm).


Minimum diameters in Group III were seen in the distobuccal canal (cervical third - 0.86 mm, middle third - 0.46 mm and apical third -0.38 mm) whereas in Group IV it was seen in the mesiobuccal canal (cervical third - 0.78 mm, middle third - 0.50 mm and apical third -0.39 mm).

Length and Angulation of the roots

[Table - 4] shows the length and angulations of the roots in all the four groups. In group I, the distal root showed the maximum measurement i.e 9.0 mm as compared to the mesial root, which had a maximum of 8.7 mm. The table also showed that in Group I, the angulations of the mesial root (34.9°) was more than that of the distal root (28.5°).

In Group II, the mean length of the distal root (9.2mm) was more than the mesial (8.5 mm) and the mesial root were more angulated (36.2°) than the distal root (25.8°).

In Group III, the distobuccal root showed maximum root length with a mean length of 7.3mm and the palatal root showed minimum root length with a mean length of 6.7 mm. The palatal root had maximum angulation (41.7°) followed by mesiobuccal root (39.7°) and the distobuccal root (34.2°) showed the least.

Conversely, in Group IV, the palatal root showed the maximum length (8.27 mm) and the distobuccal root showed the minimum length (8.06 mm). The palatal root also showed maximum angulation (41.5°), and the distobuccal showed the minimum angulation (34.2°).




   Discussion Top


It is imperative that the child′s dental integrity be kept intact for preservation of space, esthetics, prevent aberrant tongue habits, phonation, mastication and also prevent the psychologic effects associated with tooth loss.[6]

Micro-organisms are the principal etiologic factors for pulpal and periapical pathology. Therefore, the therapeutic goal of root canal therapy is to render the canal system bacteria free.

Several methods were used to investigate the anatomy of the root canals, such as direct observation with the aid of a microscope (Sempira and Hartwell, 2000);[7] macroscopic sections (Salama et al, 1992);[4] filling of canals with inert material and then decalcification (Rosenthiel, 1957);[8] filling of canals and clearing (Ayhan et al, 1996).[9] But all these methods had serious limitations, as most of the relationship of the external structure to the pulp was lost during preparation of samples.[6] A significant constraint of conventional radiography is the superimposition of overlying structures, which obscures the object of interest.

Tachibana and Matsumoto (1990)[10] studied the applicability of Computerized Tomography to endodontics. They concluded that this method allowed the observation of the morphology of the root canals, the roots and the appearance of the tooth in every direction. Moreover, the image could be analyzed, altered and reconstructed by the computer.

In this study, in all the samples the number of roots in group I were two i.e., mesial and distal, but there was variation in group II where in 2 of the samples there were 2 roots and one distal root in all the samples. In Group IV all the samples had three roots i.e., mesiobuccal, distobuccal and palatal roots. Zurcher[3] made reference to the occurrence of the two-rooted type maxillary molar and mentioned considerable variation in the number of canals. In this study, out of 15 samples in Group III, 8 samples had fused palatal and distobuccal roots but there is not much variation seen in the root canals and all had two root canals.

The number of root canals observed in mandibular molars varied from three to four. Almost invariably there were two canals in the mesial root in both mandibular molars. In group I, 93.3% had two mesial root canals and in Group II, all the samples had two mesial canals. But in the distal root, two root canals were seen in 60% and 53.3% in both Group I and II respectively. It was interesting to find 3 distal canals in one of the samples in Group II.

In Group III, in 14.2% of the samples, two mesiobuccal canals were observed and the rest of the samples had only one canal in each of the roots. More variations were observed in Group IV, especially in the mesiobuccal root where in 53% of the samples, two canals were present as compared to the distobuccal and palatal roots where two canals were present in 26% and 40% respectively.

Most of the variations within the root canals of the primary molars observed in this study were in the buccolingual dimension, which would not be detected in clinical radiographic examination.

From the measured diameter of the root canals in this study, the primary molars did exhibit tapering of the canals towards the apex but not uniformly and rather like a ribbon-shaped canal system as described by Ash.[12] It was seen that the measurement of the canals diameter in the cervical third and middle third did not show much difference, but the apical third showed some amount of apical constriction.

Cross-sections at various levels revealed that the root canal anatomy varied from round to oval or triangular. In the lower primary molars, the canals are widened buccolingually in the form of a ribbon in both mesial and distal canals and when only one root canal is present in the distal root there may be constriction in its center, reflecting the outside contour of the root. On the other hand, in the upper primary molars, the canals followed the general contour of the tooth and resembled a triangle with rounded corners.

In this study, it was observed that the angulations of the mesial root was more in both group I and II (34.9° and 36.2° respectively) as compared to the distal root (28.5° and 25.8°)- In group III and IV, maximum angulation was seen in the palatal roots (41.7° and 41.5° respectively).

The length of the roots of the primary molars, in group I, both mesial and distal roots showed somewhat the same length i.e 7.57 mm and 7.51 mm respectively. In group II, the distal root (9.24 mm) were longer than the mesial root (8.59 mm) and in group III, the distobuccal root (7.32 mm) showed the longest measurement in contrast to what Zurcher had observed. However, in group IV, the palatal root (8.27 mm) showed the longest measurement. There was a discrepancy between the length of the roots of the primary molars observed in this study and the length of roots given by Ash. The explanation for this may be that in this study the area with a greatest constriction was taken as a cervical line (or radiographic cervical line) and measurements were made from this line. Whereas Ash had taken the cementoenamel junction as a cervical line and used a Boley gauge to take the measurement. Also racial difference may be the reason as in this study samples were collected from an Indian population. From this study, the following conclusions were drawn

  1. It was not uncommon to find the distobuccal and palatal roots of the maxillary molars fused. When fusion of these two roots occurred it does not mean that the canals are also fused.
  2. The mesial root canals of the mandibular molars and the mesiobuccal root canals of the maxillary molars showed more frequent and greater variations than did the distal and distobuccal root canals of these molar teeth.
  3. The primary root canal has a ribbon-shaped root canal system and the apical portion is less constricted without uniform tapering of the root canals. So, a root canal system with a graceful, tapering canal and a single apical foramen ending at the apical foramen is the exception rather than the rule.
  4. Most of the variations within the root canals of the primary molars were observed in the buccolingual dimension which would not be detected in clinical radiographic examination.
  5. The length of the roots are more variable in the maxillary molars but in the mandibular molars the distal root is invariably longer than the mesial root.
  6. It is also not uncommon to have two well developed and separated mesial roots in the lower primary molars but this may be more prevalent in the second molar.


 
   References Top

1.Hibbard ED, Ireland RL. Morphology of the root canals of the Primary molar teeth. ASDC J Dent Child 1957;24:250-7.  Back to cited text no. 1    
2.Mayo VC, Montgomery S, del Rios C. A Computerized method for evaluating Root Canal Morphology. JOE. 1986;12:2-7.  Back to cited text no. 2    
3.Zurcher E. The anatomy of the root canals of the teeth of the Deciduous dentition and of the 1st permanent molar. William Wood 8s Co., New York.  Back to cited text no. 3    
4.Salama FS, Anderson RW, et al. Anatomy of Primary incisors and molars Root Canals. Int J Pediatr Dent. 1992;14;117-8.  Back to cited text no. 4    
5.Nielsen BR, Alyassin AM, Peters DD, Carnes DL, Lancaster J. Micro-Computed Tomography: An advanced System for Detailed Endodontic. JOE. 1995;21:561-8.  Back to cited text no. 5    
6.Simpson I. An investigation of root canal anatomy of primary teeth. J Canad Dent Ass 1973;9:634-40.  Back to cited text no. 6    
7.Sempira HN, Hartwell GR. Frequency of Second Mesiobuccal Canals in Maxillary Molars as Determined by Use of an Operating Microscope: A Clinical Study. JOE. 2000;26:673-4.  Back to cited text no. 7  [PUBMED]  
8.Rosenthiel E. Transparent model teeth with pulp. Dental Digest 1957;63:154.  Back to cited text no. 8    
9.Ayhan H, Alacam A, Olmoz A. Apical microleakage of primary teeth root canal filling materials by clearing technique. J Clin Pediatr Dent 1996;20:113-7.  Back to cited text no. 9    
10.Tachibana H, Matsumoto K. Applicability of X-ray Computerised tomography in endodontics. Endod Dent Traumatol 1990;6:16-20.  Back to cited text no. 10  [PUBMED]  
11.Sarkar S, Rao AP. Numbers of Root Canals, their shape, configuration, accessory root canals in radicular pulp morphology. A preliminary study. J Indian Soc Pedo Prev Dent 2002;20:93-97.  Back to cited text no. 11    
12.Ash MM. Wheeler's Dental Anatomy, Physiology and Occlusion, 6th Ed.  Back to cited text no. 12    


Figures

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

Tables

[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6], [Table - 7], [Table - 8], [Table - 9], [Table - 10]


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