 It is characterized by presence of normal enamel but atypical dentin with abnormal pulpal morphology.Witkop in 1972 classified DD into two types which are Type I (DD-1) is the radicular type, and type II (DD-2) is the coronal type.DD-1 has been further divided into 4 different subtypes (DD-1a,1b,1c,1d) based on the radiographic features.