retrognathism retrognathism retrognathia is a type of malocclusion which refers to an abnormal posterior positioning of the maxilla or mandible, particularly the mandible, relative to the facial skeleton and soft tissues. not to be confused with micrognathism. retrognathismother namesretrognathisma child with treacher collins syndrome showing microtia and retrognathism awaiting corrective surgeryspecialtymedical genetics, dentistry a retrognathic mandible is commonly referred to as an overbite, though this terminology is not used medically.