INTRODUCTIONrnDentin dysplasia type I (DD-I, OMIM:125400) is a rare, autosomal-dominant, heritable, non-syndromic disorder characterized by obliterated pulp chambers, diminutive roots, and severe hypermobility of teeth.1–4 This is also often combined with frequent periapical radiolucencies in apparently sound teeth, both in the deciduous and permanent dentitions, with an estimated incidence of 1/100000.5–7 DD-I increases the risk of early tooth loss and causes functional and esthetic disturbances. The initial information on DD-I mainly originated from reports of isolated cases owing to a low incidence. The genetic defects underlying DD-I were subsequently identified by genetic screen-ing in affected families. To date, gene mutations in SMOC2, VPS4B, and SSUH2 in three affected families from different countries have been identified, which strongly suggests that this disease is genetically heterogeneous.4,8–10 Despite major advancements in knowledge regarding molecular and cellular involvement in DD-I, the pathogenesis of this dysplasia remains undefined.