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 Table of Contents  
Year : 2017  |  Volume : 5  |  Issue : 2  |  Page : 258-260

Fusion of a primary mandibular lateral incisor and canine: A rarity

Department of Oral and Maxillofacial Pathology and Microbiology, D. Y. Patil University School of Dentistry, Mumbai, Maharashtra, India

Date of Web Publication15-Dec-2017

Correspondence Address:
Treville Pereira
Department of Oral and Maxillofacial Pathology and Microbiology, D. Y. Patil University School of Dentistry, Sector, Nerul, Navi Mumbai - 400 706, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/amhs.amhs_78_17

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Fusion is a developmental anomaly of dental hard tissues characterized by the union of two adjacent teeth. It may be complete with the formation of an abnormally large tooth or incomplete with the union of crowns or roots only. The exact cause is still unknown. This report describes a case of unilateral fusion of the primary lateral incisor and canine in a 6-year-old female patient who accompanied her parents for dental treatment and later had a checkup herself during one of the visits to the dental clinic. Medical history was noncontributory while there was no family history of dental anomalies. An intraoral examination revealed that mandibular right primary lateral incisor was fused to the primary canine. The permanent central incisors were erupting lingually. The intraoral periapical radiograph showed a bifid pulp chamber with a normal-sized root canal. Since the tooth was noncarious, a preventive approach with a periodic follow-up was planned.

Keywords: Anomaly, esthetics, tooth germ

How to cite this article:
Pereira T. Fusion of a primary mandibular lateral incisor and canine: A rarity. Arch Med Health Sci 2017;5:258-60

How to cite this URL:
Pereira T. Fusion of a primary mandibular lateral incisor and canine: A rarity. Arch Med Health Sci [serial online] 2017 [cited 2023 Mar 23];5:258-60. Available from: https://www.amhsjournal.org/text.asp?2017/5/2/258/220832

  Introduction Top

Teeth are complex anatomic structures that encounter developmental anomaly of various aspects, such as defects in their structure, shape, size, and number. Fusion is commonly recognized as the unification of two discrete dental buds, and the condition may arise at any stage of the dental organ. During the developmental stage, the teeth are united in the dentin region, and the pulp chambers and canals may be interconnected or separated. Fusion involves the union of epithelial and mesenchymal germ layers resulting in irregular tooth morphology.[1]

The union between a normal tooth bud and a supernumerary tooth germ can also be seen in cases of fusion. When this occurs, the numbers of teeth is reduced if the anomalous tooth is counted as a single tooth. This is contrary to what happens in gemination, where an incomplete division of a tooth occurs resulting in a large tooth crown that has a single root and canal. Fusion is one of the most unusual anomalies of shape observed in teeth.[2],[3] The effect of pressure or physical forces producing close contact between two developing teeth has been speculated as one of the probable causes of fusion.[4] Other causative factors, such as racial and genetic predisposition, have also been reported.[5] The prevalence of fusion in the primary dentition is reported to be in the range of 0.1%–3%, with no sex predilection. It can be seen unilaterally or bilaterally in either the maxillary or mandibular dentition.[6] Malalignment, dental caries, periodontal, and esthetic problems are the multifaceted complications that can occur due to this rare developmental anomaly.[7] A frequent finding in the fusion of primary teeth is the congenital absence of the corresponding permanent tooth. A multidisciplinary approach may be indicated in the clinical management of problems associated with fused teeth.[8]

Here, we report a rare case of fusion between the right mandibular primary lateral incisor and canine in a 6-year-old female patient.

  Case Report Top

A 6-year-old girl accompanied her parents for dental treatment at the D. Y. Patil University's teaching hospital in October 2016. During one of their visits, her mother insisted that the child receive a routine dental checkup, and it was incidentally discovered during the examination that the girl had fusion – a rare dental anomaly. The patient's medical history was noncontributory. There was no family history of dental anomalies, and no consanguinity was reported in the parents. General and extraoral examinations appeared noncontributory. An intraoral examination revealed that the mandibular right primary lateral incisor and primary canine were fused together [Figure 1]. There was a deep groove on the labial and lingual surfaces that was not affected either by dental caries or periodontal problems. The right mandibular primary canine was missing. There was a lingual eruption of permanent mandibular central incisors. The patient had an early mixed dentition. The rest of the dentition was normal, without any variations or anomalies. Intraoral periapical radiographs showed the presence of a large tooth with a bifid pulp chamber and a normal-sized root canal [Figure 2]. Proper instructions regarding the maintenance of oral hygiene were given to the patient to avoid caries. A multidisciplinary approach that included orthodontic treatment to ensure functional occlusion and esthetics was explained to the parents. Since there were no carious lesions present, a preventive approach using fissure sealants and topical fluoride, along with a six monthly periodic follow-up, was planned.
Figure 1: Intraoral photograph showing the primary mandibular right lateral incisor and canine fused together and the permanent central incisors erupting lingually

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Figure 2: Intraoral periapical radiograph showing the fusion of the right mandibular primary lateral incisor and canine along with erupting permanent central incisors

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  Discussion Top

Fusion of the tooth is the union of two separate tooth germs. There may be a complete or incomplete tooth fusion, depending on the time of union and the stages of tooth development. It may occur involving two normal teeth or sometimes between a normal tooth and supernumerary tooth germ.[2]

The term “fusion” is considered when the number of teeth in the dental arch is reduced. If the number of teeth in the dental arch is normal, then it is termed “germination” or it is a case of fusion between a normal and a supernumerary tooth.[9] In the present case, the number of teeth in the dental arch was reduced in number. Very few cases of fusion in mandibular primary dentition have been reported in the Indian population. Etiological factors could be physical forces or pressure causing contact of the developing teeth; also trauma, viral infection during pregnancy, or a genetic basis that could possibly be an autosomal dominant trait with a reduced penetrance has been suggested. Thalidomide embryopathy may also induce fusion. Fusion has also been reported with congenital anomalies such as cleft lip and X-linked congenital conditions.[10] Fusion can be classified as complete and incomplete. Complete fusion begins before calcification with the crown showing the features of both the participating teeth as regards to the enamel, dentin, cementum, and pulp. Incomplete fusion occurs at a later stage where the tooth might show separate crowns and the level of fusion is limited to the roots with the pulp canals being fused or separate.[2]

Comprehensive history, clinical features, and radiographic findings are the principal criteria for the diagnosis of tooth fusion.[10] Clinically, a fused tooth is broad and shows either a groove delineating the two crowns, an incisal notch, or a bifid crown. The groove may continue onto the root if the teeth are also conjoined, but maxillary-fused teeth often show two roots. Fusion may be partial, involving only the crowns, or total, involving the tooth crown and root. Fused teeth may involve pulp chambers dividing the tooth into two root canals or two independent endodontic systems.[11] In the present case, a groove was noticed between the crowns of the right mandibular lateral incisor and the right mandibular canine only in the incisal third, and their roots were fused completely to form a single root canal. Accumulation of bacterial plaque takes place in the deep groove present on the surface of the fused tooth, which leads to dental caries and periodontal disease.[9] To prevent dental caries, the application of fissure sealants on the grooves between the two components is recommended in the fused primary teeth.[12] Radiographs should be taken to check for other developmental anomalies. Thorough follow-up at the appropriate time is necessary to prevent delayed exfoliation and eruption of the successors. The greater root surface area of fused primary teeth may delay exfoliation by root resorption. This can also cause delayed resorption of the root due to greater root mass and an increased area of root surface relative to the size of the permanent successor crown. In cases where esthetics is of concern with no other underlying factors, a conservative use of tooth reshaping, direct composite bonding, or porcelain veneers and crowns has been recommended.[12] Various methods such as selective grinding, surgical separation, reconstruction, or extraction are included, followed by prosthesis.[4]

This developmental anomaly needs to be recorded during routine clinical examination. The abnormal morphology demands prophylactic and early interceptive treatment, to avoid the complicated pulpal and periodontal treatment related to these teeth. Very few cases of fusion in mandibular primary dentition have been reported from the Indian population. In Caucasians, it is 0.02%, and in Japanese population, it is 0.32%.[9]

The fusion of primary teeth usually is asymptomatic, but its presence may result in disturbances in the eruption of permanent teeth. Fusion of the primary lateral incisor and cuspid might result in early loss of the cuspid, along with a potential loss of arch length or midline shift. To prevent this complication, preservation of arch space and form should be considered. Surgical extraction of the affected primary teeth can be an option to avoid its delayed exfoliation and the subsequent delayed or ectopic eruption of the successor.

In the present case, there was a lingual eruption of the permanent central incisors. The parents were cautioned about the possibility of crowding in the anterior teeth and early exfoliation of the primary teeth.

Tooth fusion is an anomaly affecting the shape of a tooth, and tooth fusion in mandibular primary teeth has very little documentation in the Indian population. Management of tooth fusion depends on the morphology of the fused tooth and the knowledge and skills of the dental practitioner.[13] Clinical observation, along with an orthopantomograph, periapical radiographs, and intervention at the appropriate time are of paramount importance. These conditions require a minimal intervention approach, preventive procedures, and long-term follow-up.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Neena IE, Sharma R, Poornima P, Roopa KB. Gemination in primary central incisor. J Oral Res Rev 2015;7:55-7.  Back to cited text no. 1
  [Full text]  
Pereira AJ, Fidel RA, Fidel SR. Maxillary lateral incisor with two root canals: Fusion, gemination or dens invaginatus? Braz Dent J 2000;11:141-6.  Back to cited text no. 2
Tewari N, Pandey RK. Bilateral fusion in primary mandibular teeth: A report of two cases. J Indian Soc Pedod Prev Dent 2011;29:50-2.  Back to cited text no. 3
[PUBMED]  [Full text]  
Rajashekhara BS, Dave B, Manjunatha BS, Poonacha KS, Sujan SG. Bilateral fusion of primary mandibular lateral incisors and canines: A report of a rare case. Rev Odontol Ciênc 2010;25:427-9.  Back to cited text no. 4
Turell IL, Zmener O. Endodontic therapy in a fused mandibular molar. J Endod 1999;25:208-9.  Back to cited text no. 5
Wu CW, Lin YT, Lin YT. Double primary teeth in children under 17 years old and their correlation with permanent successors. Chang Gung Med J 2010;33:188-93.  Back to cited text no. 6
Muthukumar RS, Arunkumar S, Sadasiva K. Bilateral fusion of mandibular second premolar and supernumerary tooth: A rare case report. J Oral Maxillofac Pathol 2012;16:128-30.  Back to cited text no. 7
  [Full text]  
Mehta V. Bilateral fusion in mandibular primary anterior teeth: Report of a rare case with a brief review of literature. Dent Open J 2017;4:10-2.  Back to cited text no. 8
Bharghav M, Chaudhary D, Aggarwal S. Fusion presenting as germination – A rare case report. Oral Maxillofac Pathol J 2012;3:211-4.  Back to cited text no. 9
Rao PK, Mascarenhas R, Anita A, Devadiga D. Fusion in deciduous mandibular anterior teeth – A rare case. Dentistry 2014;S2:001. [Doi: 10.4172/2161-1122.S2-001].  Back to cited text no. 10
Penumatsa NV, Nallanchakrava S, Dandempally A. Fusion of mandibular primary incisors and their permanent successors: A case report with review of literature. J Oral Res Rev 2012;4:56-9.  Back to cited text no. 11
Sharma D, Bansal H, Sandhu SV, Bhullar RK, Bhandari R, Kakkar T. Fusion: A case report and review of literature. J Craniomaxillofac Dis 2012;1:114-8.  Back to cited text no. 12
Mohtesham I, Shakil M, Jose M, Prabhu V. Fusion of deciduous central incisors. Arch Med Health Sci 2015;3:85-7.  Back to cited text no. 13
  [Full text]  


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