The specific name of the anomaly shown in the following radiograph is:
Dens in Dente 
(Dens invaginatus, dilated composite odontome)
The  ‘dens in dente’  is a  developmental variation which is thought to arise as a result of an invagination in the surface of tooth crown before calcification has occurred. Several causes of this condition have been proposed. These include increased localized external pressure, focal growth retardation, and focal growth stimulation in certain areas of the tooth bud. The permanent maxillary lateral incisors are the teeth most frequently involved,  and in the majority of cases the  ‘dens in dente’ appears to represent simply an accentuation in the development of the lingual pit.
Radiological signs
Dens in dente represent a tooth-shaped, enamel-covered mass within the crown and/or root of the tooth but which may traverse the length of the tooth. Dilated odontome represents the most extreme form of this anomaly and exhibits a grossly altered morphology that is internally outlined by a dense linear radiopacity. In both cases, the apical region may or may not display an open apex and there may be associated adjacent apical rarefaction.
Dens in dente
Dilated odontome
Dens invaginatus
Ghost tooth