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. The gene discussed is VPS4B; the disease is dentin dysplasia type I.