Case Report

Fusion of Primary Mandibular Teeth Associated with Partial Anodontia of Permanent Dentition: A Case Report

Vivek Mehta


Fusion is a developmental disturbance in the shape of teeth. It is defined as the dentinal union of two embryologically developing teeth. It is more commonly seen in primary dentition and more frequently in incisor region. This paper reports a case that had the presence of fused primary central incisor and lateral incisor in the mandibular region associated with agenesis of permanent left central incisor.


Key words: Anodontia; Developmental Disturbance; Fusion; Primary Incisors; Mandibular teeth.


Vivek Mehta. Fusion of Primary Mandibular Teeth Associated with Partial Anodontia of Permanent Dentition: A Case Report. International Journal of Oral & Maxillofacial Pathology; 2015:6(1):23-25. © International Journal of Oral and Maxillofacial Pathology. Published by Publishing Division, Celesta Software Private Limited. All Rights Reserved.



The dentinal union of two embryological developing teeth leading to one less tooth than normal in the affected arch is known as Fusion. It is a dental twinning anomaly and has been described by many terms like double teeth, conjoined teeth, twinned teeth. Clinically, the appearance of the involved teeth may be normal sized or large, depending upon the stage at which embryological union occurs during development. It is commonly confused with gemination that is an incomplete attempt of one tooth bud to divide into two. Fused teeth are more common in primary dentition as compared to permanent dentition. The occurrence is 0.5% in primary dentition, 0.1% in the permanent dentition and 0.02% for bilateral involvement in primary dentition.1 It is more frequently seen in mandibular primary incisors.2 Males and females are equally affected. Genetics may be an important factor when there is an increased incidence.3 The presence of double teeth can cause a lot of clinical problems like delayed resorption of roots thereby resulting in delayed or ectopic eruption of permanent teeth.4 A frequent finding in fusion of primary teeth is the congenital absence of permanent teeth and the prevalence depends upon the combination of fused primary teeth.5


Case Report

A four-year-old girl reported to the Department of Pediatric and Preventive Dentistry with the chief complaint of decayed teeth in the lower arch. The family and medical history of the child patient were non- contributory. Thorough intraoral examination showed a primary dentition with carious involvement of mandibular right and left primary second molars.


The mandibular arch revealed an asymmetry in the tooth number. There were four teeth on the left side and five teeth on the right side. The mandibular right primary central and lateral incisors were present along with an enlarged bifid crown i.e. 71 and 72 [Figure 1a]. Intraoral periapical radiograph revealed that the enlarged bifid crown was due to fusion of the 71 and 72 teeth (mandibular left primary central incisor and primary lateral incisor). The affected tooth showed the fusion of crown and roots resulting in joined pulp canal through pulp chambers [Figure 1b]. An orthopantogram was taken which revealed fused mandibular primary central and lateral incisor and missing tooth buds of permanent left central incisor [Figure 1c]. The fused tooth had one root and two pulp chambers and two root canals. The succedaneous permanent mandibular left central incisor was missing. The parents of the child patient gave no history of trauma. A thorough general examination was carried out to rule out the presence of any associated syndrome.



Fused teeth can be found in almost any region of the dental arch and in both primary and permanent dentitions. A lot of theories have been suggested to explain the causes of fused teeth but according to the most accepted theory it results from contact between developing teeth due to some physical force or pressure.6 The union may be total or partial and it may also occur between a normal and a supernumerary tooth.7 Fusion can be classified into complete and incomplete types. In complete fusion the union begins before calcification and crown of the fused tooth incorporates features of both teeth, but in incomplete fusion union of teeth occur at a much later stage and tooth might exhibit separate crown and fusion may be limited to roots with pulp canals fused or separate.7


Figure 1: The clinical picture of mandibular enlarged bifid crown irt 71 and 72 (a). The periapical radiograph (b) and Orthopantamogram (c) of involved 71 and 72 teeth illustrated joined pulp canals through pulp chambers and missing 31.


Fused teeth may be present bilaterally with hypodontia8 or with partial anodontia of primary and permanent dentition,9 but this case report presents a case of unilaterally fused teeth associated with agenesis of permanent tooth. Most of the fused teeth are associated with occlusalS disturbances, space problems, aesthetic and periodontal problems.10 The fissure present at the union between fused teeth predisposes it to caries and periodontal disease. The larger root surface area of fused primary teeth may result in delayed resorption of root and this may lead to ectopic resorption of the permanent successor.4 The presence of fused teeth can also cause aesthetic problems, especially in the anterior region. The treatment of fused teeth depends on the clinical situation; patientŐs expectations and degree of compliance.11 Proper instructions regarding maintenance of oral hygiene should be given to the patient to avoid caries. Fissure sealants can be used as they reduce the risk of caries. A multidisciplinary approach can also be used to ensure functional occlusion and aesthetics.


In the present case restoration of 75 and 85 was done with glass ionomer cement and fused primary teeth were retained as such as they were free from caries. Preventive approach was planned that included topical fluoride application, dietary alterations, oral hygiene instructions and periodic follow-ups.



A thorough clinical and radiographic evaluation is necessary to detect the presence of double teeth in primary dentition. Early diagnosis is the key to management. Fused teeth in primary dentition may be associated with anomalies in permanent dentition. It is important to recognize this dental anomaly, as it will facilitate the establishment of a right treatment with multidisciplinary view.



We would like to thank the staff members from the Department of Oral and Maxillofacial Pathology for their support.


Author Affiliations

Dr. Vivek Mehta, Assistant Professor, Department of Pediatric Dentistry, Faculty of Dentistry, Jamia Millia Islamia University, New Delhi-110025,



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Corresponding Author

Dr. Vivek Mehta

Assistant Professor

Dept. of Pediatric Dentistry

Faculty of Dentistry,

Jamia Millia Islamia University

New Delhi-110025

Ph: +91 9212024943




Source of Support: Nil, Conflict of Interest: None Declared.


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