- An attempt at division of a single tooth before calcification, resulting in incomplete formation of two teeth.
- The resultant structure will have two completely or incompletely separated crowns with a single root and root canal.
- It is difficult to differentiate between gemination and a case in which there has been fusion between a normal tooth and a supernumerary tooth.
Twinning:
The division of a single tooth resulting in one normal and one supernumerary tooth. The number of teeth will be more than normal.
Concrescence:
- A form of fusion of cementum after completion of root formation
- The teeth are united by cementum only.
- Maxillary molars are frequently involved
Fusion:
- Union of two normally separated tooth germs.
- If the union occurs before calcification, the two teeth are completely united to form a single Large tooth.
- If the union occurs after calcification, there is union of roots only. The tooth may have separate or fused root canals.
- Fusion of teeth is more common in deciduous teeth.