Definition: A single developing tooth germ attempts to divide but is incomplete resulting in an abnormally larger than normal tooth. The overall tooth count is still 16 for an arch. This is sometimes referred to as twinning.
Radiographic Features:
Location: More common in primary teeth in the anterior but can occur anywhere (maxillary and mandibular teeth)
Edge: Well-defined.
Shape: Tooth shape.
Internal: Radiopaque and radiolucent. Radiopacity of tooth structure (enamel and dentin). Radiolucency of soft tissue (pulp chamber and root canal space).
Other: None
Number: May be single or multiple.
Gemination
Mandibular third molar
(looks like two molars creating one massive molar)
Can Fusion be a better option than gemination.
Whenever one becomes two ,(germination)the two twins created should in most cases smaller.
Like wise when two molars(actual and a supposed supernumerary) try to fuse it tends to look bigger.
Fusion would require one less tooth in an arch – 15 instead of 16 in an arch. And surprisingly when one becomes two they are not always smaller and sometimes the second one is about the same size as the original.