Tooth development is a complex process of reciprocal interactions
that we have only recently begun to understand. With the large number
of genes involved in the odontogenic process, the opportunity for
mutations to disrupt this process is high. Tooth agenesis (hypodontia)
is the most common craniofacial malformation with patients missing
anywhere from one tooth to their entire dentition. Hypodontia can
occur in association with other developmental anomalies (syndromic)
or as an isolated condition (non-syndromic). Recent advances in genetic
techniques have allowed us to begin understanding the genetic processes
that underlie the odontogenic process and to identify the mechanisms
responsible for tooth agenesis. Thus far two genes have been identified
by mutational analysis as the major causes of non-syndromic
hypodontia;PAX9 and MSX1. Haploinsufficiency of either has been
observed to cause the more severe forms of hypodontia whilst point
mutations cause hypodontia to varying degrees of severity. With the
prevalence of hypodontia having been observed to have increased during
the 20
century, the future identification and analysis of its genetic
basis is essential to allow us to better treat the condition. The clinician
can facilitate this process by collaborating with the human geneticist
and referring patients/families with familial hypodontia for investigative
research.