Gemination, Twinning, Concrescence and Fusion of Teeth

Gemination:

• 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.