Signs and Symptoms
- Chewing difficulty and damage to adjacent structures
- Deviation in occlusion
- Asymmetry of dental arch due to enlarged crown
- Aesthetic problem
- Delay or obstruction of adjacent tooth eruption

Cause
- Unknown cause, but possible factors include vitamin deficiency, hormonal irregularities, infection or inflammation near developing tooth bud, drug-induced, genetic predisposition, and radiotherapy damage to tooth germ

Mechanism
- Gemination occurs when two teeth develop from one tooth bud, resulting in an extra tooth
- Fusion is the union of two normally separated tooth germs, which can be complete or incomplete
- Geminated teeth have incomplete division, resulting in a large tooth crown with a single root and canal
- Gemination is an asymptomatic condition
- Prevalence of gemination or fusion is 2.5% in primary dentition and 0.1-0.2% in permanent dentition

Diagnosis
- Clinical examination
- Radiographs showing two crowns arising from a single root

Treatment
- Maintain good oral hygiene to prevent plaque accumulation
- Use fissure sealants and resin restorations to prevent dental caries in deep grooves and fissures
- Consider orthodontic treatment
- Reshape and restore teeth with appropriate materials
- Perform root canal treatment, followed by reduction of medio-distal width and crown restoration
- Surgical division of the tooth into two teeth if root canal treatment is not suitable
- Extraction may be considered if the tooth is not suitable for root canal treatment, followed by fixed or removable prosthetic if needed
- Transplantation of supernumerary teeth to replace the geminated tooth
- Thorough knowledge of root canal morphology is necessary to avoid complications before root canal treatment or extraction

Related abnormalities of the dentition
- Amelogenesis imperfecta
- Dentinogenesis imperfecta
- Hyperdontia (more than average number of teeth)
- Anodontia (lack of tooth development)