Hypodontia UMLS:C0020608 Hypodontia needs to be confirmed by X-rays. The terms hypodontia and oligodontia have been used interchangeably in literature but these define two different clinical entities. Hypodontia has been used to define exclusively the absence of permanent teeth and excluding third molars, but the absence of any deciduous and permanent teeth, including third molars, should be called hypodontia as well. HP:0000668 SNOMEDCT_US:64969001 The absence of five or less teeth from the normal series by a failure to develop. Missing between one and six teeth Failure of development of between one and six teeth Tooth agenesis