Oligodontia is the lack of tooth development of 6 or more permanent teeth, without an associated systemic disorder. Hypodontia is the absence of 6 or less teeth, but is usually part of a more complex set of developmental problems. Most cases of tooth agenesis involve hypodontia. Researchers have recently discovered a number of genes and gene products which control communication between and within the cells that are necessary for tooth formation. Examples of extracellular signals are bone morphogenetic proteins and fibroblast growth factors.
Genes are the molecular code of life.
The 46 human chromosomes contain approximately 100,000 genes. Three billion information bases make up these 100,000 genes. These genetic mistakes may then be passed on from generation to generation as mendelian inheritance traits. Familial tooth agenesis can be transmitted as an autosomal dominant , autosomal recessive, or X-linked condition. Recent studies have found that mutations in two regulatory genes, MSX-1 and PAX9, cause tooth agenesis.