Hereditary Defects of Tooth Dentin. Recent Progress on Genetic Aetiology Suggests for Modifications of the Existing Classification System

Hereditary defects of dentin include dentinogenesis imperfecta (DGI) and dentin dysplasia (DD). They are characterized by abnormal dentin for­ mation. Within the last 32 years, since the first classification system was pro­ posed, significant advances have been made regarding their genetic aetio­ logies. In the classification system suggested by Shields et al (1973), den­ tinogenesis imperfecta type I (DGI­I) is associated with some types of osteo­ genesis imperfecta (OI), which is caused nearly in all cases by mutations of the genes encoding type I collagen (Col1A1 and Col1A2 genes). However, a more specific relationship between the type of OI, the genetic defect and the dental involvement can not been established. As far as isolated dentin defects are concerned, 10 mutations all occurring in different sites of the DSPP gene have been described to cause DGI­II, DGI­III and DD­II. No information about the gene defects in DD­I is currently available. Plenty of new evidence suggests that the existing classification system should be revised at least as far as the types of dentinogenesis imperfecta II and III are concerned.