Orthognathic Surgery Class 3 or Mandibular Prognathism

What is Mandibular Prognatism and how is it treated?

Mandibular prognathism, derived from the Latin word pro, meaning “forward", and the Greek word gnathos, meaning “jaw, is a facial deformity which is described as the presence of an anteroposterior discrepancy between the mandible and the maxilla. That is, both jawbones are misaligned.

In cases of mandibular prognathism, the mandible is overdeveloped in relation to the maxilla. In dental terminology, mandibular prognathism is also known as class III.

Facial features with this type of problem tend to appear slightly hard and aggressive.

Mandibular prognathism is diagnosed when:

  • The mandible presents abnormal overdevelopment with respect to the maxilla, which is considered a skeletal problem.
  • The patient has excess chin projection.
  • The prominent jaw is caused by a dental problem, that is, when the teeth are misaligned.


Orthognathic surgery as solution to mandibular prognathism or class III  solves functional problems such as erradicating discomfort when chewing, and pain in the temporomandibular joint (TMJ). In addition, there is also a great aesthetic improvement after surgery: facial features become softer, finer and more harmonious.


The three conventional solutions to this problem are, respectively:

  • Bimaxillary orthognathic surgery, where the maxillofacial surgeon needs to operate on both the mandibular and the maxillary bone, or monomaxillary orthognathic surgery, where the surgeon acts on only one of the two skeletal structures. Depending on the case, orthognathic surgery should be accompanied by orthodontic treatment.
  • Mentoplasty or chin reduction surgery.
  • Orthodontic treatment.