Mutations in DSPP cause a range of autosomal dominant dental diseases, including dentin dysplasia type 2 (DD-II),(20) dentinogenesis imperfecta type 2 (DGI-II),(21) and dentinogenesis imperfecta type 3 (DGI-III).(22) To date, no other gene besides DSPP has been associated with isolated inherited dentin defects.(2,14) Dspp null mice display severe dentin malformations,(23) while transgenic expression of only the N-terminal domain (Dsp) in the null background partially rescues the dentin phenotype.(24) The volume of dentin but not the dentin mineral density is restored. The gene discussed is DSPP; the disease is dentinogenesis imperfecta type 3.