Birth defects of the jaw include
Micrognathia
Agnathia
Maxillary hypoplasia
Micrognathia is a small lower jaw (mandible). Pierre Robin sequence and Treacher Collins syndrome, which are disorders characterized by several defects in the head and face, are associated with a small lower jaw. If the lower jaw is too small, the infant may have difficulty eating or breathing. Surgery to extend the jaw may correct or diminish the problem.
Agnathia, a condition in which a part of or the entire lower jaw is missing, is a severe malformation. Often the infant also has abnormalities of the ears, temporal bone, saliva glands, the muscles used in chewing, and facial nerve. Treatment of agnathia consists of reconstructive surgery with bone grafts and other tissue grafts to improve the appearance and function of the jaw.
Maxillary hypoplasia is underdevelopment of the upper jaw (maxilla). It causes a flat mid-face, which makes the lower jaw appear to stick out. Treatment of maxillary hypoplasia involves surgery to reposition the upper jaw and align it with the lower jaw.
Doctors diagnose all of these defects by assessing the degree of jaw underdevelopment with x-rays Plain X-Rays X-rays are high-energy radiation waves that can penetrate most substances (to varying degrees). In very low doses, x-rays are used to produce images that help doctors diagnose disease. In high... read more and computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more 
(CT) of the face.
(See also Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Birth defects of the face and limbs are fairly common. They may involve only a specific body part, such as the mouth (cleft lip or cleft palate) or foot (clubfoot). Or they may be part of a... read more .)
