Dentin dysplasia is a genetic defect of dentin formation inherited as an autosomal dominant trait. It is characterized by normal enamel but atypical dentin formation with abnormal pulpal morphology. Once thought to be a single entity, dentin dysplasia has now been divided into type I (radicular) and II (coronal). Type I is by far the more common. Both types include multiple/generalized involvement of primary and permanent dentition. Combinations of both types have also been described in the literature. Four distinct forms of dentin dysplasia type I and 1 form of dentin dysplasia type II are identified. Although there seems to be no need to identify more than 2 distinct types of this relatively rare inherited defect of human dentin, the possible existence of additional forms of the disease cannot be ruled out. Here is a case report of dentin dysplasia in a single tooth, with crown and roots of normal dimensions, associated with severe pain and mobility and histologically involving both coronal and radicular dentin. Focal odontoblastic dysplasia or dentin dysplasia type III could be the new entity.