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 Table of Contents  
CASE REPORT
Year : 2016  |  Volume : 7  |  Issue : 2  |  Page : 121-123

Gemination of a mandibular third molar: A rare case report


1 Department of Oral Pathology and Microbiology, Subharti Dental College and Hospital, Meerut, Uttar Pradesh, India
2 Department of Oral and Maxillofacial Surgery, Subharti Dental College and Hospital, Meerut, Uttar Pradesh, India

Date of Web Publication19-May-2016

Correspondence Address:
Arvind Venkatesh
Department of Oral Pathology and Microbiology, Subharti Dental College and Hospital, Meerut, Uttar Pradesh
India
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DOI: 10.4103/0976-433X.182674

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  Abstract 

The disturbances in the shape of the teeth include gemination, fusion, concrescence, dilaceration, talon cusp, dens in dente, dens evaginatus, taurodontism, and supernumerary roots. Gemination is defined as a single enlarged tooth or joined tooth in which the tooth count is normal when the anomalous tooth is counted as one, even though the exact pathogenesis may be questionable. Gemination is more common in the deciduous dentition compared to permanent dentition. This condition is rarely associated with mandibular third molars, and the terminology has often been a topic of debate when the condition in associated with this tooth. Here, we present a case of gemination associated with the mandibular third molar, showing an unusual and distinct crown and root morphology. The clinical and radiographic features, pulp chamber, and root canal morphology using stereomicroscopy and the histological features of the tooth have been discussed in detail.

Keywords: Double teeth, fusion, gemination, twinning


How to cite this article:
Venkatesh A, Goel S, Wadhwan V, Bansal V. Gemination of a mandibular third molar: A rare case report. SRM J Res Dent Sci 2016;7:121-3

How to cite this URL:
Venkatesh A, Goel S, Wadhwan V, Bansal V. Gemination of a mandibular third molar: A rare case report. SRM J Res Dent Sci [serial online] 2016 [cited 2020 Oct 22];7:121-3. Available from: https://www.srmjrds.in/text.asp?2016/7/2/121/182674


  Introduction Top


Numerous developmental alterations of teeth can occur. They can be broadly classified as primary or secondary arising due to environmental influences. Variations in the number of teeth that develop are the commonest of the alterations.[1] The developmental disturbances in the shape of the teeth include gemination, fusion, concrescence, dilaceration, talon cusp, dens in dente, dens evaginatus, taurodontism, and supernumerary roots.[2] Here, we present a case of gemination in mandibular third molar — a rare entity, by itself, showing atypical coronal and radicular morphology.


  Case Report Top


A 50-year-old male patient reported with the chief complaint of pain in the right lower back tooth region for the past 15 days. The patient gave no significant medical or dental history. Clinical examination revealed pain on percussion in relation to 48 (as per, FDI tooth numbering system) [Figure 1]a. There was no related swelling or discharge in relation to the tooth.
Figure 1: (a) Clinical appearance of mesioangular impacted 48. (b) Orthopantomograph showing impacted 48 with a distal crown-like structure. (c) Buccal view of extracted tooth. (d) Lingual view of extracted tooth. (e) Occlusal view of the mesial crown. (f) Occlusal view of the distal crown

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Orthopantomogram showed a radio-opaque crown like structure attached to the distal surface of the crown of mesioangular impacted 48 with a well-defined radiolucency surrounding this structure. Enamel and dentin like structures could be appreciated in the distal crown like structure. The mesial and the distal crowns showed distinct pulp chambers leading into the root canal [Figure 1]b.

Based on the radiographic findings, a differential diagnosis of gemination in relation to 48 or fusion of 48 with a distomolar/supernumerary tooth was made.

Surgical removal of the tooth in toto was carried out under local anesthesia.

The extracted tooth consisted of two crown like structures-mesial and distal; with the distal crown angulated from the mesial crown and the root [Figure 1]c and [Figure 1]d. The mesial crown of the right mandibular third molar showed an atypical morphology with 4 cusps (mesiobuccal, mesiolingual, distobuccal, and distolingual) with a prominent oblique ridge extending from the mesiolingual cusp to the distobuccal cusp [Figure 1]e.

The distal crown had two cusps which were unequal in size (a large mesial cusp and a smaller distal cusp) [Figure 1]f. The roots also showed atypical morphology.

The tooth had 3 roots, a broad buccal root [Figure 1]d and two lingual roots (mesiolingual and distolingual) which were about 2 mm longer than the buccal root [Figure 1]e.

Radiographic evaluation of the extracted specimen showed enamel and dentin like structures in both the crowns with the pulp chamber showing a Y-shaped morphology. Both the mesial and the distal crowns had a well-defined pulp chambers which were continuous apically as 3 root canals, the buccal, mesiolingual, and the distolingual canals, respectively.

The tooth was hemi-sectioned buccolingually. Stereo microscopic evaluation of the buccal segment showed well-defined pulp chambers in relation to both mesial and the distal crowns which continued in the root as a single root canal, thus showing a typical Y-shaped canal morphology [Figure 2]a, whereas, the lingual segment showed well-defined mesial and distal pulp chambers giving rise to two root canals, correspondingly, the mesiolingual and the distolingual canals [Figure 2]b.
Figure 2: (a) Sectioned buccal segment showing pulp chamber and root canal morphology. (b) Sectioned lingual segment showing pulp chamber and root canal morphology. (c) Stereomicroscopic appearance of the ground section of the tooth. (d) Light microscopic view of the ground section showing cementum-like material over the enamel surface (×400)

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The buccal segment was used to prepare a ground section, and the lingual segment was decalcified using 10% nitric acid and subjected to routine tissue processing and histopathological evaluation.

Stereomicroscopic view of the ground section showed normal enamel, dentinal tubules, and pulp chambers. The mesial and distal crowns had well-defined pulp chambers which continued as a single root canal apically [Figure 2]c. Under light microscopy, generalized deposition of cementum-like material was appreciated over the surface of the enamel in both the crowns [Figure 2]d.

The decalcified segment was stained with hematoxylin and eosin stain which showed a normal pattern of the dentinal tubules and two distinct root canals originating from the pulp chamber.

Based on the clinical, radiological, and stereomicroscopic features, the tooth was determined to be gemination of mandibular third molar.


  Discussion Top


The mandibular third molar varies considerably in different individuals and presents many anomalies both in form and in position. However, its design usually conforms to the general plan of all mandibular molars.[3] In the present case, the mandibular third molar has 4 cusps with a prominent oblique ridge kind of structure extending from the mesiolingual to the distobuccal cusp contributing to the uncommon anatomy of the tooth.

Mandibular third molars generally present with two roots, but anatomic variants are also not uncommon. The present case showed three roots, two on the lingual aspect and one on the buccal aspect. According to a study conducted by Guerisoli et al., 0.9% of analyzed mandibular third molars among 114 teeth demonstrated three-root morphology.[4] Sidow et al. reported that 5% of cases showed 3 rooted morphology amongst the mandibular third molars.[5]

Double teeth are two separate teeth exhibiting union by dentin and their pulps. The union may be the result of the fusion of two adjacent tooth buds (fusion) or the partial splitting of one into two (gemination).[1]

If one tooth germ by division — shizodontia, forms two equal teeth, the term gemination is used. This depends on the time when this force influences the formation whether the division of the crown will be partial or complete (bifid crown). In complete division, two separate crowns with their own pulp chambers and one common root are formed. Gemination is more frequent in primary than in permanent teeth. Fusion is quite an opposite process — synodontia, which is uniting two or more tooth germs (separate tooth organs during embryonic development). Fusion can be complete (total) or incomplete (partial), it depends on time when the force causing the narrowing of the space between the tooth germs was at work. When the fusion is complete one tooth is formed, and this leads to a reduced number in the dental arch. In cases of partial fusion, there is one crown with separate roots. There can also be one common pulp chamber.[6]

The etiology of double teeth formation is generally unclear. Many theories connect environmental influences, genetics, trauma, systemic disease, the lack of vitamins, and lack of space in the dental arch as possible causes of this anomaly.[7] Clinically, these abnormalities manifest themselves in higher caries incidence, malocclusion, changes in the length of the dental arch, periodontal diseases, hyper or hypodontia of the successional tooth, anomalies in the eruption of the successional tooth and poor esthetics.[8] Double teeth occur in both the primary and permanent dentitions, with a higher frequency in the anterior and maxillary regions. The overall prevalence is around 0.1% in a permanent dentition.[1] Milazzo and Alexander have for the purpose of a differential diagnosis suggested counting of teeth: A normal number of teeth in the dental arch indicate gemination, a reduced number fusion. An exception are cases where there is a normal tooth fused with a supernumerary one, or when there is a gemination in a dental arch with hypodontia.[6] Hence, as in the present case, it is difficult to classify the condition as gemination or fusion. Various authors cite that the term “double teeth” can be generally used to mention teeth falling under this category.[7] There have also been suggestions that the term gemination and fusion should be discontinued, and all of these anomalies should be termed twinning.[1] By definition, gemination is defined as a single enlarged tooth or joined tooth in which the tooth count is normal when the anomalous tooth is counted as one, even though the exact pathogenesis may be questionable.[1]

Hence, for the current case, it is evident from the definition that the term gemination can be used as a diagnosis even though it is unclear whether the resultant tooth is due to the division of one tooth germ or union of two tooth germs to form a single structure.


  Conclusion Top


Gemination in the posterior permanent dentition is an uncommon condition and is extremely rare, but they are important dental anomalies that could affect any tooth in the mouth.

Identification of the condition and radiographic evaluation is mandatory prior to any treatment involving these variations of teeth for their successful outcome.

 
  References Top

1.
Neville BW, Damm DD, Allen CM, Bouquot JE. Oral and Maxillofacial Pathology. 3rd ed. Philadelphia: Saunders; 2009.  Back to cited text no. 1
    
2.
Rajendran R, Sivapathasundaram B. Shafer's Textbook of Oral Pathology. 7th ed. New Delhi: Elsevier; 2012.  Back to cited text no. 2
    
3.
Nelson SJ, Ash MM Jr. Wheeler's Dental Anatomy, Physiology and Occlusion. 9th ed. St. Louis: Saunders; 2012.  Back to cited text no. 3
    
4.
Guerisoli DM, de Souza RA, de Sousa Neto MD, Silva RG, Pécora JD. External and internal anatomy of third molars. Braz Dent J 1998;9:91-4.  Back to cited text no. 4
    
5.
Sidow SJ, West LA, Liewehr FR, Loushine RJ. Root canal morphology of human maxillary and mandibular third molars. J Endod 2000;26:675-8.  Back to cited text no. 5
    
6.
Knezevic A, Travan S, Tarle Z, Sutalo J, Jankovic B, Ciglar I. Double tooth. Coll Antropol 2002;26:667-72.  Back to cited text no. 6
    
7.
Méndez P, Junquera L, Gallego L. Double teeth. Br Dent J 2007; 202:508-9.  Back to cited text no. 7
    
8.
Gupta R, Prakash V, Sharma M. Endodontic and post-endodontic management of a fused molar. Indian J Dent Res 2013;24:274-6.  Back to cited text no. 8
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