Union between the dentin or enamel of two separate developing primary or
permanent tooth germ ,one of which may be supernumerary.
Fused teeth have separate pulp chambers and root canals .
If you count the teeth clinically number of teeth may be reduced ,except if fusion occurred with supernumerary.
iv-Gemination
Represent an attempted division of a single tooth germ by
invagination during the proliferation stage of growth.
Usually one root and one root canal is present.
Number of the teeth in the arch are normal or reveals an extra tooth.