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ORIGINAL ARTICLE
Year : 2018  |  Volume : 36  |  Issue : 2  |  Page : 151-157
 

Root canal morphology of primary molars by clearing technique: An in vitro study


Department of Pedodontics and Preventive Dentistry, Terna Dental College, Mumbai, Maharashtra, India

Date of Web Publication2-Jul-2018

Correspondence Address:
Farhin Katge
Department of Pedodontics and Preventive Dentistry, Terna Dental College, Sector 22, Plot No.12, Nerul (W), Mumbai - 400 706, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JISPPD.JISPPD_237_16

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   Abstract 


Objective: The objective of the study was to study root canal morphology of primary molars by clearing technique and to observe for any variations. Materials and Methods: One hundred and twenty extracted primary molars were divided into four groups (n = 30); Group I = maxillary first, Group II = maxillary second, Group III = mandibular first, and Group IV = mandibular second. The samples were subjected to decalcification, clearing, and dye penetration. The data regarding the root canal morphology of each sample were tabulated based on the number of root canals, curvature of the root canal, and root canal configuration. Descriptive statistics were applied. Results: According to Vertucci's root canal configuration in Group I, mesiobuccal root exhibited 93.10% Type I, 6.90% Type II, and 6.90% Type IV; distobuccal root had 95.65% Type I and 4.35% Type IV; and palatal roots had 100% Type I canal configuration. In Group II, mesiobuccal root showed 90% Type I and 10% Type IV; distobuccal root had 100% Type I; palatal root exhibited 96.30% Type I and 3.70% Type III. In Group III, mesial root showed 20% Type I, 6.67% Type III, and 73.33% Type IV and distal root had 76.67% Type I and 23.33% Type IV. In Group IV, mesial root exhibited 100% Type IV and distal root had 43.33% Type I and 65.67% Type IV canal anatomy. Conclusion: Vertucci's Type I root canal configurations were most frequently observed.


Keywords: Clearing, dye, primary molars, root canal morphology


How to cite this article:
Katge F, Wakpanjar MM. Root canal morphology of primary molars by clearing technique: An in vitro study. J Indian Soc Pedod Prev Dent 2018;36:151-7

How to cite this URL:
Katge F, Wakpanjar MM. Root canal morphology of primary molars by clearing technique: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2018 [cited 2019 Dec 11];36:151-7. Available from: http://www.jisppd.com/text.asp?2018/36/2/151/235683





   Introduction Top


The difficulties in endodontic therapy are due to unique anatomy of primary teeth. For successful treatment of primary teeth, the clinician must have a thorough knowledge of the anatomy of primary teeth and the variations that exist within them.[1] Accessory canals and the ever-present resorption of root ends add to the problem of successful endodontic therapy in primary teeth.[2] Premature loss of a primary tooth can cause many problems including loss of arch perimeter, supraeruption of opposing teeth, and changes in the patient's occlusion.[3]

The variations in root canal anatomies have long been linked to various racial and genetic patterns.[4],[5],[6],[7] The aim of this study is to research the root canal anatomy of primary molars by clearing technique and look for any variations. A thorough knowledge of the root canal morphology will help us in understanding and delivering the best possible treatment outcome.


   Materials and Methods Top


Approval to conduct the study was sought and obtained from the Institutional Review Board of Ethics. The study was carried out in the Department of Paedodontics and Preventive Dentistry. One hundred and twenty extracted primary molars were used for the study and were divided into four groups consisting of thirty teeth in each group [Figure 1]:
Figure 1: Samples collected; (a) Group I, (b) Group II, (c) Group III, (d) Group IV

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  • Group I: Primary maxillary first molars
  • Group II: Primary maxillary second molars
  • Group III: Primary mandibular first molars
  • Group IV: Primary mandibular second molars.


The extracted teeth were collected from different dental colleges and private clinics. As the samples were not extracted for the purpose of this study, the exact data about age and sex of individual sources were unknown.

Inclusion criteria

  • Extracted teeth with at least two intact roots
  • At least two-third length of each root.


Exclusion criteria

  • No evidence of furcation involvement of teeth
  • External root resorption more than one-third of root length
  • Fractured root.


The sample teeth were washed under tap water in a glass container for 30 min and immersed in 3% sodium hypochlorite (Mumbai Healthcare Industries, Mumbai, Maharashtra, India) for 30 min to remove adherent soft tissue. Any remaining adherent soft tissue was physically scraped using a scalpel blade. An ultrasonic scaler was used to remove calculus or stains. Subsequently, during the period of the study, the teeth were stored in distilled water with thymol iodide crystals.[8]

Coronal access cavity was prepared using BR 46 DIA-BURS (Mani, Japan) and Endo-Z bur (Dentsply Maillefer, Ballaigues, Switzerland) at high speed, under cooling with distilled water [Figure 2]. The samples were then immersed in 6% hydrochloric acid (Qualigens Fine Chemicals, Mumbai, Maharashtra, India) at room temperature for decalcification.[4] The hydrochloric solution was changed regularly and frequently agitated because demineralization occurs at the top of the static acid rather than the bottom. At the end of decalcification, the teeth were washed in running tap water for 1 h.
Figure 2: Access opening done in tooth samples; (a) Group I, (b) Group II, (c) Group III, (d) Group IV

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The teeth were then kept in varying concentrations of ethanol for dehydration. The sequence of concentrations of ethanol employed was 60%, 70%, 80%, 90%, and 100% (Analytical reagent, China) consecutively for 5 h each.[4] For clearing, the teeth were immersed in a solution containing methyl salicylate and absolute ethanol in a ratio of 1:1 for 6 h. The teeth were then immersed in methyl salicylate solution (Qualigens Fine Chemicals, Mumbai, Maharashtra, India) to render them transparent. The teeth were placed on an absorbent tissue paper for 2 h and allowed to dry. Drying is necessary to aid the penetration of ink in the next stage.

A plastic disposable endodontic irrigating syringe with a 30-gauge needle was used to inject the methylene blue dye (Qualigens Fine Chemicals, Mumbai, Maharashtra, India) into the coronal end of canal orifice. At the same time, a suction tip was placed at the root apex to draw out the excess ink through the root canal. The appearance of ink at the apical foramen indicated the end of the process. The transparent specimens were dipped in methyl salicylate and examined by the naked eye as well as a magnifying lens (×3) under a halogen light to improve the coefficient of refraction. The data regarding the root canal morphology of each sample were tabulated based on the number of root canals, curvature of the root canal (straight, curved, and S-shaped) [Figure 3], and root canal configuration (Vertucci's classification) [Figure 4]. Photographs of the specimens were taken with a DSLR camera (600-D, Canon, Japan) with lens (18–55 mm 0.25 m/0.8 ft EFS macro). Two independent examiners recorded all the above parameters of root and root canal morphology. Descriptive statistics were used to determine the frequency for all the four groups using the SPSS version 21 software package (SPSS Inc., Chicago, IL, USA).
Figure 3: Curvature of canals; (a) Curved, (b) Straight, (c) S-shaped

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Figure 4: Type of canals according to Vertucci's; (a and b) Vertucci's type I; (c and d) Vertucci's Type IV

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   Results Top


Group I: Primary maxillary first molars [Table 1]
Table 1: Frequency of number, curvature, and type of root canals in primary maxillary first molars (Group I)

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According to inclusion criteria, teeth with two intact roots were considered for this study. Out of 30 teeth, 29 mesiobuccal roots, 23 distobuccal roots, and 27 palatal roots were intact which were considered for the study. Mesiobuccal canal was curved in 21 (72.41%) teeth, straight in 7 (24.14%) teeth, and S-shaped in 1 (3.45%) tooth. Distobuccal canal was curved in 11 (47.83%) teeth and straight in 12 (52.17%) teeth. The palatal canal was curved in 3 (11.11%) teeth and straight in 24 (88.89%) teeth. Mesiobuccal root had one canal in 26 (89.66%) teeth and two canals in 3 (10.34%) teeth. Distobuccal root had one canal in 22 (95.65%) teeth. Palatal root had a single canal in all 27 (100%) teeth. Mesiobuccal root had Type I root canal configuration in 27 (93.10%) teeth and Type II and IV in 2 (6.90%) teeth. Distobuccal root had Type I in 22 (95.65%) teeth and Type IV in 1 (4.35%) teeth. Palatal roots had Type I in 27 (100%) teeth.

Group II: Primary maxillary second molars [Table 2]
Table 2: Frequency of number, curvature, and type of root canals in primary maxillary second molars (Group II)

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In Group II, all thirty mesiobuccal roots were intact, whereas 25 distobuccal roots and 27 palatal roots were intact. Mesiobuccal canal was curved in 20 (66.67%) teeth and straight in 10 (33.33%) teeth. Distobuccal canal was curved in 15 (60%) teeth, straight in 9 (36%) teeth, and S-shaped in 1 (4%) tooth. The palatal canal was curved in 24 (88.89%) teeth and straight in 3 (11.11%) teeth. Mesiobuccal root had one canal in 27 (90%) teeth. Distobuccal root had a single canal in all the teeth. Palatal root had one canal in 26 (96.30%) teeth and two canals in only one (3.70%) tooth [Graph 1]. Mesiobuccal root had Type I root canal configuration in 27 (90%) teeth and Type IV in 3 (10%) teeth. Distobuccal root had Type I in 25 (100%) teeth. Palatal root had Type I in 26 (96.30%) teeth and Type III in 1 (3.70%) tooth.



Group III: Primary mandibular first molars [Table 3]
Table 3: Frequency of number, curvature, and type of root canals in primary mandibular first molars (Group III)

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Mesial root had a single canal in 6 (20%) teeth and two canals in 24 (80%) teeth. Distal root had one canal in 23 (76.67%) teeth and two canals in 7 (23.33%) teeth.

Mesial root having single mesial canal was curved in 2 (33.33%) teeth and straight in 4 (66.67%) teeth. The two canals in mesial root were mesiobuccal and mesiolingual canals. Mesiobuccal canals were curved in 17 (70.83%) teeth and straight in 7 (29.17%) teeth. Mesiolingual canals were curved in 9 (37.50%) teeth and straight in 15 (62.50%) teeth. Distal root with single canal was curved in 8 (34.78%) teeth and straight in 15 (65.22%) teeth. The two canals in distal root were distobuccal and distolingual canals. Straight distobuccal canal was present in 5 (71.43%) teeth, whereas straight distolingual canal was present in 15 (62.50%) teeth.

Mesial root had Type I in 6 (20%) teeth, Type III in 2 (6.67%) teeth, and Type IV in 22 (73.33%) teeth. Distal root had Type I in 23 (76.67%) teeth and Type IV in 7 (23.33%) teeth.

Group IV: Primary mandibular second molars [Table 4]
Table 4: Frequency of number, curvature, and type of root canals in primary mandibular second molars (Group IV)

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Mesial root had two canals in 30 (100%) teeth. Distal root had one canal in 13 (43.33%) teeth and two canals in 17 (56.67%) teeth. Mesiobuccal canal was curved in 17 (56.67%) teeth and straight in 13 (43.33%) teeth. Mesiolingual canal was curved in 18 (60%) teeth and straight in 12 (40%) teeth. Distal root with two canals consisted of distobuccal and distolingual canals. Both distobuccal and distolingual canals were curved in 58.82% of teeth. Distal root with one canal was curved in 8 (61.54%) teeth. Mesial root had Type IV in 30 (100%) teeth. Distal root had Type I in 13 (43.33%) and Type IV in 17 (65.67%) teeth [Graph 2].




   Discussion Top


One of the predominant causes of failure of root canal treatment in primary molars is the variation in root canal anatomy. Several methods have been used to investigate the morphology of root canals in extracted teeth; all have been shown to have limitations.[5],[6],[7],[8],[9]

In the conventional radiographic method, to study the buccolingual aspect of the roots, the teeth should be sectioned into two or three parts, which lead to loss of overall tooth structures. Although computed tomography is a useful method for studying the morphology of root canals, it requires an expensive device and trained personnel. The main problem associated with filling canals with inert materials and subsequent tooth decalcification with a strong acid is a loss of structures external to the pulp during sample preparation.

Tooth clearing has been employed to obtain information on various aspects of endodontic treatment including morphology.[10],[11],[12] Various techniques have been used to clear teeth, and a number of demineralizing agents have been proposed.[13],[14],[15]

It has been reported that shrinkage of organic tooth tissue could occur during the demineralization process and that this phenomenon may be avoided if a weak concentration of acid is used.[16] A clearing technique was described by Okumura and Robertson et al. for studying the root canal anatomy.[16],[17],[18]

The clearing method used in the present study is based on similar techniques that have been followed by Bagherian et al. and Gupta and Grewal in their research on root canal morphology of primary molars.[4],[12] The clearing technique resulted in very clear specimens, allowing excellent visualization of the canal anatomy, which was evident in the photographs taken. The root canal morphology of the cleared teeth was examined under halogen light and observations were recorded. The root canal morphology was studied in the primary teeth using Vertucci's classification which is accepted worldwide.[19]

Curved and straight profiles of the root canals were dominant in all the groups. S-shaped curvature was observed in 1 (3.45%) mesiobuccal canal of maxillary first molar and 1 (4%) distobuccal canal of the maxillary second molar. Gupta and Grewal conducted a study on root canal configuration of mandibular first molars using decalcification and clearing method. The authors observed straight canals in 100% of mesiobuccal root canals, 93.33% of mesiolingual canals, and 100% in distal canals.[12] The present study showed straight canals in 29.17% of mesiobuccal canals and 62.50% of mesiolingual canals. Since the curvature of the root canals may pose problems such as perforations during the cleaning procedures, more detailed knowledge of the frequency of these curvature types may be beneficial for avoiding this kind of complication.

In maxillary molars, all three roots (mesiobuccal, distobuccal, and palatal) most commonly consisted of a single canal. Zoremchhingi et al. used computerized tomography and showed that two canals were most frequently present in both mesial and distal roots of mandibular molars.[20] In the present study, the mesial root of mandibular molars showed more frequently two canals within the root. The distal root of mandibular molars demonstrated most commonly, one canal (76.67%) in first molars and two canals (56.67%) in mandibular second molars.

Gupta and Grewal found that, in mesial root, 100% of the samples had Vertucci's Type I root canal configuration. In the distobuccal root, Type I was found in 93.33% of the specimens and 6.67% of the specimens had Type IV root canal configuration. In the distolingual root canal, 100% of the specimens had Type I root canals.[12] According to the study conducted by Bagherian et al., in mandibular first molars, mesial root had Type IV in 81.50% and distal root had Type I in 77.80%.[4] In the present study, mandibular first molars showed Type IV in 73.33% mesial root and Type I in 76.67%, whereas maxillary first molars had dominant Type I root canal configuration. The number of root canals in Classes II, III, and IV was very similar to those reported by Zoremchhingi et al. and Hibbard ED et al.[20],[21]

In the present study, we used an inexpensive clearing technique that allowed observation of the teeth in three dimensions. However, this method destroys the enamel structure during decalcification, and the tooth structure cannot be preserved. Another limitation of this technique is that the methylene blue dye spreads rapidly throughout the tooth structure within 30 min causing difficulty in studying the root canal morphology. Injection of the dye under high pressure into the root canals before decalcification and clearing may help to solve this problem.


   Conclusion Top


All the three roots of maxillary molars consisted of single canal. Mesial root of mandibular first (80%) and mandibular second (100%) molars showed two canals frequently. Most of the canals of the sample teeth were either straight or curved. Mesiobuccal canal of maxillary first molar and distobuccal canal of maxillary second molar exhibited one S-shaped canal each.

When the root canal configurations were categorized using Vertucci's classification, Type I was most frequently observed. The canals which frequently showed Type IV were mesial roots of mandibular first molars and both (mesial and distal) roots of mandibular second molars.

Further studies need to be conducted with the larger sample size so as to simplify the understanding of this complex system of root canal morphology.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Tagger M, Katz A, Tamse A. Apical seal using the GPII method in straight canals compared with lateral condensation, with or without sealer. Oral Surg Oral Med Oral Pathol 1994;78:225-31.  Back to cited text no. 15
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    Figures

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

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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