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 Table of Contents  
Year : 2019  |  Volume : 31  |  Issue : 4  |  Page : 377-381

Gemination mandibular third molar – A rare case with use of CBCT in diagnosis and treatment planning

1 Department of Oral Medicine and Radiology, R.R. Dental College and Hospital, Umarda, Udaipur, Rajasthan, India
2 Department of Oral and Maxillofacial Surgery, Pacific Dental College and Hospital, Debari, Udaipur, Rajasthan, India
3 Department of Oral Medicine and Radiology, Pacific Dental College and Hospital, Debari, Udaipur, Rajasthan, India
4 Department of Prosthodontics, Darshan Dental College and Hospital, Loyra, Udaipur, Rajasthan, India

Date of Submission29-Aug-2019
Date of Acceptance20-Dec-2019
Date of Web Publication03-Mar-2020

Correspondence Address:
Dr. Pooja Bhatt
Department of Oral Medicine and Radiology, R.R. Dental College and Hospital, Udaipur-313 015, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiaomr.jiaomr_156_19

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It is not uncommon to find dental anomalies in routine practice. Developmental dental anomalies may be seen in tooth number, size, shape, and structure. Gemination and fusion are anomalies of shape with close similarity but with different etiology. Differential diagnosis is difficult and so the term “double teeth” is often used. The incidence of double teeth is less than 1% and even more so in permanent dentition. Here, we present a unique case of gemination in mandibular third molar diagnosed effectively with the help of three-dimensional imaging and managed with the surgical technique.

Keywords: Double teeth, fusion, gemination

How to cite this article:
Bhatt P, Gupta H, Mathur H, Porwal A. Gemination mandibular third molar – A rare case with use of CBCT in diagnosis and treatment planning. J Indian Acad Oral Med Radiol 2019;31:377-81

How to cite this URL:
Bhatt P, Gupta H, Mathur H, Porwal A. Gemination mandibular third molar – A rare case with use of CBCT in diagnosis and treatment planning. J Indian Acad Oral Med Radiol [serial online] 2019 [cited 2022 May 26];31:377-81. Available from: https://www.jiaomr.in/text.asp?2019/31/4/377/279855

   Introduction Top

Tooth development is a complex process that occurs under the effect of numerous genetic and environmental factors. As a result of alterations in these factors, numerous alterations of teeth can occur. Of these, variations in the number of teeth are the commonest anomaly seen.[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]

The anomaly of conjoined teeth has been described by different terms such as gemination, fusion, double teeth, and twining. These definitions of fusion or gemination are based on the way the tooth was developed. Gemination occurs as a result of the attempted division of a single tooth germ, whereas fusion arises through the union of two normally separated tooth germs.[3] Therefore, a convenient method to diagnose remains to count the number of teeth in the dental arch. If fused teeth are counted as one and the number of teeth in the dental arch is less, then the term fusion is used. However, when the abnormal tooth is counted as one and the number of teeth in the dental arch is normal then it is termed as gemination. A point of confusion occurs in the case of fusion between normal and supernumerary tooth.

The clinical and routine radiographic examination may provide information for diagnosis which might not be conclusive in some cases due to their inherent limitations. Since dental anomalies represent a three-dimensional (3D) change that may occur throughout the dental surface, a careful investigation is required to obtain a more accurate diagnosis and appropriate treatment. The purpose of this article is to report a rare occurrence of gemination in the third molar region where cone-beam computed tomography was used to determinate the diagnosis and to help in surgical planning.

   Case Report Top

A 23-year-old female patient reported with the chief complaint of pain in the left lower back tooth region for the past 10 days. The patient gave no significant medical or dental history. Clinical examination revealed partially erupted 38 with redness and swelling of pericoronal flap. In light of history and clinical picture, a provisional diagnosis of pericoronitis i.r.t partially erupted 38 was made and radiographic examination was advised.

Orthopantomogram (OPG) [Figure 1] showed a mesioangular impacted 38 and a radio-opaque distinct crown-like structure attached to the distal surface of 38 root. Enamel and dentin-like structures were appreciated in the distal crown-like structure. A well-defined homogenous radiolucency distal to 38 and anomalous crown-like structure suggestive of pericoronal bone loss was noted.
Figure 1: Section of orthopantomogram (OPG) showing the distal crown-like structure and pericoronal radiolucency

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Based on the radiographic findings, a differential diagnosis of gemination in relation to 38, a fusion of 38 with a distomolar/supernumerary tooth and presence of compound odontoma were considered.

A supernumerary tooth commonly shows aberrant; conical or tuberculated form. The present case showed a distinct molar crown-like structure attached to the third molar; an uncommon site for odontoma presentation. The root anatomy was not clearly appreciated and OPG revealed 38 proximity to the left mandibular canal. Thus, for the elucidation of anatomy and confirmatory diagnosis, CBCT imaging was advised.

CBCT scan of the left posterior mandible region was taken with CS 8100 3D digital imaging system (Carestream Dental LLC, Hatfield, PA) with 80 kVp tube voltage and 10 mA tube current. CBCT images of 38 region revealed two crown-like structures: mesial (crown/tooth I) and distal (crown/ tooth II); with the distal crown angulated buccally within the anterior border of left ramus and showed close approximation to the inferior alveolar canal. The mesial crown (crown I) revealed typical molar anatomy showing 5 cusps—mesiobuccal, distobuccal, distal, mesiolingual, and distolingual. The distal crown (crown II) also showed 5 cusps showing comparable morphology [Figure 2].
Figure 2: Orientation of tooth 38. Morphology of crown I and crown II

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Homogenously hypodense pericoronal area of bone loss was noted i.r.t crown II with loss of crestal bone. Discrete coronal pulp chambers were seen with respective crowns. The complex root anatomy encountered was interpreted by a series of multiplanar images [Figure 3], [Figure 4], [Figure 5], which revealed that radicular region of tooth I bifurcates to form buccal and lingual roots. The buccal root housing the mesiobuccal root canal and the lingual root accommodating mesiolingual and distal root canals was noted. At the point of bifurcation, the distal root canal (lingual root) fuses with the tooth II pulp chamber and continues now as a single broad lingual root and root canals in I–II configuration. Both roots showed about 2–2.5 mm distance from the inferior alveolar canal [Figure 4].
Figure 3: Axial sections 38 showing: pericoronal bone loss i.r.t crown II. The fusion of distal root canal tooth I with pulp chamber tooth II. Fused lingual root and separate buccal root. The proximity of crown II with inferior alveolar nerve canal (IANC)

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Figure 4: Cross-sections 38 showing lingual root and root canal tooth I continuous with tooth II and its pulp chamber. No separate root/root canals distinguished with the latter. Relative distances of buccal, lingual roots, and crown II with IANC

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Figure 5: Sagittal sections (buccal to lingual) showing separate buccal root 38. Distolingually fused root and root canals of tooth I and II. Proximity crown II with IANC

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The presence of distinct crowns of comparable morphology with common roots narrowed the diagnostic dilemma ruling out odontoma. When fusion takes place between a normal tooth and a supernumerary tooth, the fused teeth show an anomalous broad crown with separate roots which were contrary to the current scenario. On the other hand, a bifid crown is a diagnostic feature of gemination. Based on above evidences, the radiographic diagnosis of the gemination of the third molar was concluded.

Following this, necessary blood investigations were done and surgical extraction of 38 was planned. Careful surgical removal of the tooth was carried out under local anesthesia [Figure 6]. The teeth were spliced for convenient extraction with minimal trauma [Figure 6]. Two separate molar crowns with common roots were identified indicating an incomplete division of single tooth germ. A definitive diagnosis of gemination 38 was given. Post-extraction sutures were placed, medications prescribed, and the patient was followed up for postoperative healing, which was uneventful.
Figure 6: Intra- and postoperative pictures. Note two crowns with common roots

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   Discussion Top

Double teeth may develop during tooth bud morpho differentiation as a result of the developmental aberration of the ectoderm and mesoderm under the effect of local metabolic interferences.[4]

The etiology remains uncertain. Environmental factors, trauma, systemic diseases, vitamin deficits, or genetic predisposition have been proposed for its development.[5],[6]

If one tooth germ by division forms two equal teeth, the term gemination/shizodontia is used. This division can be partial or complete. On the other hand, fusion/synodontia is the union of two or more tooth germs. Fusion can also be complete (total) or incomplete (partial), it depends on the 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.[7]

The presentation with a normal number of teeth and an anomaly with a large bifid crown is diagnostic of gemination.[8] These anomalies are more common in deciduous teeth and very rare in permanent molars.[9],[10] It occurs predominantly in incisors and canines with equal distribution in the maxilla and mandible.A recent study reports a prevalence of 0.95% in India.[11]

It may be associated with syndromes such as achondrodysplasia and chondroectodermal dysplasia or can be found in non-syndromic patients.[12]

The clinical problems, particularly if the anterior teeth are involved, vary from tooth malalignment, spacing problems, arch asymmetry, esthetic problems, and impeded eruption of the adjacent tooth.[7] The presence of deep groove in some cases of gemination makes them susceptible to caries and periodontal diseases.[13],[14]

Diagnosing these anomalies accurately can be confusing. Complete case history, clinical examination, and radiographic investigation can provide the information required for the diagnosis of such abnormalities.[15]

Conventional plain film radiographic methods such as periapical, occlusal, panoramic, or cephalometric radiographs are standard for diagnosis and treatment planning. However, due to their inherent limitations, such as insufficient precision because of unusual projection errors and lack of information about spatial relationships, these methods are considered unreliable.[16]

The CBCT permits to execute 3D reconstructions providing information on axial, sagittal, and coronal planes with no magnification errors. It allows the visualization of the crown-root anatomy, their variations and help demarcate the portion of the teeth that present fusion. It helps assess accurate pulpal anatomy which is very useful in differentiating these double teeth. In addition, it clearly shows the anatomical relation of the inferior alveolar canal with the third molar without which an effective treatment plan is difficult to establish.[17]

Treatment options are case-based and depend upon the patient requirement, the teeth involved, and the degree of involvement. If a primary tooth is involved the treatment depends upon the presence of the succedaneous tooth.[18] Method such as selective grinding, surgical separation followed by pulp therapy of the retained segment, and orthodontic correction have been proposed to manage the condition.[19]

In our case, the offending tooth was a third molar causing pericoronal infection, so extraction was chosen over conservation for the best patient interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Neville BW, Damm DD, Allen CM, Bouquot JE. Oral and Maxillofacial Pathology. 3rd ed. Philadelphia: Saunders; 2009.  Back to cited text no. 1
Rajendran R, Sivapathasundaram B. Shafer's Textbook of Oral Pathology. 7th ed. New Delhi: Elsevier; 2012.  Back to cited text no. 2
Olivan-Rosas G, López-Jiménez J, Giménez-Prats MJ, Piqueras-Hernández M. Considerations and differences in the treatment of a fused tooth. Med Oral 2004;9:224-8.  Back to cited text no. 3
Grover PS, Lorton L. Gemination and twinning in the permanent dentition. Oral Surg Oral Med Oral Pathol 1985;59:313-8.  Back to cited text no. 4
Chen HS, Huang YL. Fusion of third and fourth mandibular molars? Oral Surg Oral Med Oral Pathol 1992;73:767-3.  Back to cited text no. 5
Tomizawa M, Shimizu A, Hayashi S, Noda T. Bilateral maxillary fused primary incisors accompanied by succedaneous supernumerary teeth: Report of a case. Int J Paediatr Dent 2002;12:223-7.  Back to cited text no. 6
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.  Back to cited text no. 7
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Hattab FN, Hazza'a AM. An unusual case of talon cusp on geminated tooth. J Can Dent Assoc 2001;67:263-6.  Back to cited text no. 8
Ferreira-Junior O, de Avila LD, Sampieri MB, Dias-Ribeiro E, Chen WL, Fan S. Impacted lower third molar fused with a supernumerary tooth—Diagnosis and treatment planning using cone-beam computed tomography. Int J Oral Sci 2009:1;224-8.  Back to cited text no. 9
Talla HV, Adamala SR, Surapaneni S, Chillakuru D. Mandibular third molar gemination: A rare anomaly. J Indian Acad Oral Med Radiol 2015;27:241-4.  Back to cited text no. 10
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Shilpa G, Gokhale N, Mallineni SK, Nuvvula S. Prevalence of dental anomalies in deciduous dentition and its association with succedaneous dentition: A cross-sectional study of 4180 South Indian children. J Indian Soc Pedod Prev Dent 2017;35:56-62.  Back to cited text no. 11
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Sekerci AE, Sisman Y, Ekizer A, Sahman H, Gusmus H, Aydinbelge M. Prevalence of double (Fused/Geminated) primary teeth in Turkey – study. Pak Oral Dental J 2011;31:7-13.  Back to cited text no. 12
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]


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