Tooth agenesis is a common kind of tooth dysplasia and it can be divided into the hypodontia, oligodontia and anodontia. The oligodontia, which can be inherited as an autosome- dominant, autosome- recessive, or X- linked trait, consists of two types: syndromic oligodontia and non - syndromic oligodontia. The oligodontia happens with familial heredity background or not. The article summarizes the relationship between the PAX 9 gene mutation of patient and the oligodontia.
