[Shafer 7th ed 40, 41/ 6th ed 40]
| Gemination | - An attempt at division of a single tooth before calcification, resulting in incomplete formation of two teeth.(AIIMS-2012)
- The resultant structures 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.
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| Twinning | - The division of a single tooth resulting in one normal and and one supernumerary tooth. The number of teeth will be more than normal
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| Concrescence | - A form of fusion of cementum after completion of root formation
- The teeth are united by cementum only.
- Maxillary molars are frequently involved.
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| 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.
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