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Year : 2015  |  Volume : 3  |  Issue : 1  |  Page : 57-58

Unusual morphology of primary mandibular first molar

Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India

Date of Web Publication4-Jun-2015

Correspondence Address:
Dr. Sidhant Pathak
Room No. 8, Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Pavillion Road, Davangere - 577 004, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2348-0149.158170

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A thorough knowledge of tooth morphology and its clinical variations is necessary for successful restorative and endodontic treatment. Primary mandibular first molars have numerous variations in its anatomy and thus poses a huge challenge for a pedodontist. This case report highlights a rare anatomical configuration of primary mandibular first molar and points out the importance of thorough clinical and radiographical examination before any treatment.

Keywords: Morphology, pedodontist, primary tooth

How to cite this article:
Poornima P, Pathak S, Nagaveni N B, Roopa K B. Unusual morphology of primary mandibular first molar. Niger J Exp Clin Biosci 2015;3:57-8

How to cite this URL:
Poornima P, Pathak S, Nagaveni N B, Roopa K B. Unusual morphology of primary mandibular first molar. Niger J Exp Clin Biosci [serial online] 2015 [cited 2022 Jul 1];3:57-8. Available from: https://www.njecbonline.org/text.asp?2015/3/1/57/158170

  Introduction Top

The human dentition is not just composed of various teeth but every tooth has a very unique morphology. [1] The primary molars are extremely important for the proper development of the muscles of mastication, the formation of jaw bones, and the maintenance of space needed for the eruption of permanent teeth. The primary mandibular first molar is morphologically unique among the primary molars. It is easily distinguishable from the other teeth in both the primary and permanent dentitions. [2],[3],[4] The clinical relevance of understanding tooth morphology lies primarily in its value in studying crown restoration and occlusion. The most important features of primary mandibular first molar related to its restorative procedures are the position and number of cusps and the outline of the crown. [1] It also tends to show a greater degree of interconnecting branches between the pulp and pulp canals. [5] For the clinical success in root canal procedures, a proper understanding of the root canal system and its variations is of utmost importance as a dentist. [6]

This paper presents a case report, which may intensify the complexity of primary mandibular first molar variation and is intended to emphasize the clinician's awareness towards its rare crown and root morphology.

  Case Report Top

An 8-year-old boy reported to the Department of Pedodontics and preventive dentistry with the chief complaint of decayed right lower tooth. Intra-oral examination revealed moderate carious lesion in the mandibular right deciduous first molar (84). But the first primary molar was exhibiting unusual crown morphology. From the occlusal aspect, 84 was triangular in configuration with a total of 5 cusps [Figure 1]. A prominent mesiobuccal cusp was seen with distobuccal, distal, mesiolingual, and distolingual cusps being equal in size. An intraoral periapical radiograph revealed pulpal horns corresponding to all the cusps [Figure 2]. The tooth also had an extra root at the lingual aspect in relation to 84. Even though there were three roots, there was an additional canal with respect to the distal root. Glass ionomer restoration was done for the carious 84.
Figure 1: Intraoral photograph depicting 5 cusps in primary first molar

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Figure 2: Radiograph of primary first molar highlighting an extra root

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  Discussion Top

Descriptions of variations in tooth have traditionally been dependent on objective linear measurements or subjective preconceptions of shape. Ratios of crown mesiodistal and buccolingual provides a general idea of the shape of the tooth, but a variety of shapes could result within the same ratios. [1] The outline of primary mandibular first molar from the occlusal aspect has been described by terms such as rhomboid, oval, rectangular, or quadrilateral. [2],[3],[4]

It is difficult to understand detailed differences, however, using such subjective system. Furthermore, it creates ambiguities in shape definition, due to variation within species. Two types of the coronal outline and six types of cusp alignment of primary mandibular first molar were identified and classified by Hung et al. [1] [Table 1] and [Table 2]. A study done by Hung et al. [1] on 144 Taiwanese children showed that 93% of primary mandibular first molars have four cusps (Type A, B, and C), 5% have five cusps (Type D and E), and 2% have three cusps (Type F).
Table 1: Coronal outline form

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Table 2: Cusp alignment

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A study done by Zoremchhingi et al. [7] found 2 mesial roots in 13% of primary mandibular second molars.

Routine intraoral radiographs with different angulations help in detecting the presence of extra roots. Knowledge of anatomic abnormality also helps to decrease the failure rate of root canal procedures. [6]

In our case report, Type E cuspal alignment was seen with an extra root and 5 canals in primary mandibular right first molar.

  Conclusion Top

Primary mandibular first molar has lot of variations in its crown and root morphology. The knowledge of anatomical characteristics and its possible variations is essential before its restoration or root canal treatment. Clear radiographs should be taken from different angulations to evaluate the internal tooth anatomy for its successful treatment.

  References Top

Tsai HH. Descriptive classification of variations in primary mandibular first molars. ASDC J Dent Child 2001;68:23-6, 10.  Back to cited text no. 1
Woelfel JB, Scheid RC. Dental anatomy: Its relevance to dentistry. 5 th ed. Baltimore: William and Wilkins; 1997. p. 307-10.  Back to cited text no. 2
Fuller JL, Denehy GE. Consice dental anatomy and morphology. 2 nd ed. Iowa: Mosby; 1984. p. 241-4.  Back to cited text no. 3
Brand RW, Isselhard DE. Anatomy of orofacial structures. 6 th ed. St. Louis: Mosby; 1998. p. 481-3.  Back to cited text no. 4
Ford PP. Harty′s Endodontics in clinical practice. 4 th ed. Oxford: Wright; 1997.  Back to cited text no. 5
Selvakumar H, Kavitha S, Bharathan R, Varghese JS. Five canalled and three-rooted primary second mandibular molar. Case Rep Dent 2014;2014:216491.  Back to cited text no. 6
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.  Back to cited text no. 7


  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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