Proteins produced from the DSPP gene are critical for normal dentin and
tooth formation. Allelic mutations in the DSPP gene cause a variety of phenotypes that
range in severity. The most common condition caused by DSPP mutations is
dentinogenesis imperfecta type II (DGI – II). The DGI –II trait is highly penetrant and
transmitted in an autosomal dominant manner. De novo mutations that cause DGI-II
occur but appear to be rare. The clinical phenotype is characterized by amber to blue
gray discoloration of both the primary and permanent dentitions and teeth that may be
normal or diminished in size and can have a marked constriction at the cementumenamel
junction. The pulp chambers tend to fill in with irregular dentin that has an
increased water content, decreased mineral content and diminished number of dentinal
tubules. The second phenotype associated with DSPP mutations is known as dentin
dysplasia type II (DD-II). This trait is essentially the same as DGI-II in the primary
dentition with an attenuated expression in the permanent dentition. The permanent teeth
tend to have normal or only slight color changes and normal crown and root
morphology. The pulp chambers are frequently abnormal in morphology with anterior
teeth often having a thistle tube shaped pulp chamber. Investigators continue to search
for phenotype-genotype relationships with over 30 DSPP gene mutations reported to
date. Investigators suggest that certain frameshift mutations lead to DD-II while others
feel there is overlap in locations of mutations and the DGI-II and DD-II phenotypes.
The specific molecular basis and mechanism for the differences in clinical phenotypes
and severities that result from these allelic DSPP mutations are not known at this time.
Keywords: DSPP, dentinogenesis imperfecta, dentin dysplasia, dental phenotype,
gene mutations.
