|Classification and external resources|
Tooth gemination is a dental phenomenon that appears to be two teeth developed from one. There is one main crown with a cleft in it that, within the incisal third of the crown, looks like two teeth, though it is not two teeth. The number of the teeth in the arch will be normal.
The phenomenon of gemination arises when two teeth develop from one tooth bud and, as a result, the patient has an extra tooth, in contrast to fusion, where the patient would appear to be missing one tooth. Fused teeth arise through union of two normally separated tooth germs, and depending upon the stage of development of the teeth at the time of union, it may be either complete or incomplete. On some occasions, two independent pulp chambers and root canals can be seen. However, fusion can also be the union of a normal tooth bud to a supernumerary tooth germ. In these cases, the number of teeth is also normal and differentiation from gemination may be very difficult, if not impossible. In geminated teeth, division is usually incomplete and results in a large tooth crown that has a single root and a single canal. It is an asymptomatic condition.
The prevalence of gemination or fusion is 2.5% in primary dentition, and 0.1 - 0.2% in permanent dentition. It is more frequently observed in primary than permanent dentition; anterior than posterior teeth; unilaterally than bilaterally. It commonly occurs in the primary upper incisors.
The cause of gemination is still unknown. However, there are a few possible factors contributing to gemination:
- Vitamin deficiency
- Hormonal irregularities
- Infection or inflammation of areas near to the developing tooth bud
- Drug induced
- Genetic predisposition
- Radiotherapy that caused damage to the developing tooth germ
- Misaligned teeth can lead to chewing difficulty and damage adjacent structures
- Occlusion affected, causing deviation 
- Asymmetry of the dental arch due to enlarged crown
- Aesthetic problem
- Delay or obstruct the eruption of adjacent tooth 
- Tooth anatomy making the surface hard to clean and increase susceptibility of dental decay and periodontal disease 
- Clinical examination
- Radiographs - shown as two crowns arising from one single root 
- Patient should be advised to maintain a good oral hygiene to prevent plaque accumulation.
- Fissure sealants and resin restorations for deep grooves and fissures to prevent dental caries.
- Orthodontic treatment 
- Reshape and restore teeth with appropriate material.
- Root canal treatment, followed by the reduction of medio-distal width of the tooth. Restore teeth with crown.
- Root canal treatment then surgically divide the tooth into two teeth.
- If the tooth is not suitable for root canal treatment, then extraction could be considered. Fixed or removable prosthetic may be needed after extraction.
- Transplantation of supernumerary teeth to replace the geminated tooth.
Before root canal treatment or extraction are carried out, the clinician should have thorough knowledge about the root canal morphology to avoid complications.
Related abnormalities of the dentition
- Amelogenesis imperfecta
- Dentinogenesis imperfecta
- Hyperdontia - More than the average number of teeth
- Anodontia - Lack of tooth development
- Süha Türkaslan, Hasan Suat Gökçe and Mehmet Dalkız (July 2017). "Esthetic Rehabilitation of Bilateral Geminated Teeth: A Case Report". European Journal of Dentistry. 1 (3): 188–191. PMC 2638247. PMID 19212565.
- E. Grammatopoulos (11 Aug 2007). "Gemination or fusion?". British Dental Journal. 203: 119–120. doi:10.1038/bdj.2007.699.
- Siavash Moushekhian, Masoud Shiehzade, Amir Shammas (June 2014). "Treatment Plan and Clinical Management of a Geminated Maxillary Lateral Incisor: A Case Report". JDMT. 3 (2): 87–90.
- "Tooth gemination in dentistry". DentaGama Dental Social Network. DentaGama. Retrieved 1 December 2017.
- Nandini DB, Deepak BS, Selvamani M, Puneeth HK (2014). "Diagnostic dilemma of a double tooth: a rare case report and review". Journal of Clinical and Diagnostic Research. 8 (1): 271–2. doi:10.7860/JCDR/2014/6556.3928. PMC 3939503. PMID 24596793.
- Spuller RL, Harrington M (1986). "Gemination of a maxillary permanent central incisor treated by autogenous transplantation of a supernumerary incisor: case report". The American Academy of Pediatric Dentistry. 8 (4): 299–302. PMID 3472179.