Dentin dysplasia type I (DD-I) is a rare human dentin disorder that may affect both the primary and permanent dentitions. The teeth present crowns with normal morphology but short or absent roots. Pulp chamber obliteration and early exfoliation of primary teeth are also observed. We describe herein the typical and atypical features of DD-I presented by a 6-year-old patient, the diagnostic rationale and assessment emphasizing the histological and scanning electron microscopic analysis and the therapeutic approach. The DD-I diagnosis in patients in the mixed dentition period is challenging, especially when only some teeth are affected.