Short answer: Retrognathia means a jaw positioned further back than it should be, while prognathism means a jaw positioned forward. Protrusion describes a forward position of the teeth or jaw, and retrusion a backward position. These terms are not a diagnosis; they are the medical names for positional relationships seen during an examination.
Terms related to jaw position
- Retrognathia: The jaw sits back. Mandibular retrognathia means a retruded lower jaw, maxillary retrognathia a retruded upper jaw.
- Prognathism: The jaw sits forward. Mandibular prognathism is a protruding lower jaw.
- Micrognathia: The jaw is small in size.
For these topics, see our pages on a retruded lower jaw, a protruding lower jaw and a retruded upper jaw.
Terms related to tooth position
- Protrusion / protrusive: Teeth tipped forward or positioned forward. A “protrusive movement” is sliding the lower jaw forward.
- Retrusion: Teeth tipped backward.
- Overjet: The horizontal distance by which the upper front teeth sit in front of the lower front teeth.
- Overbite: The vertical overlap of the upper front teeth over the lower front teeth; when excessive, it is called a deep bite.
- Bimaxillary protrusion: Both the upper and lower teeth are tipped forward.
What do Class I, II and III mean?
- Class I: A normal relationship between the molars; there may be crowding or spacing.
- Class II: A relationship in which the lower teeth are behind the upper teeth; often seen with protruding front teeth.
- Class III: A relationship in which the lower teeth are in front; seen with a protruding lower jaw or a retruded upper jaw.
If these terms appear in your report
The terms describe what the clinician sees; they do not say whether treatment is needed or which method is suitable. For that, age, growth stage, facial profile and X-ray measurements are assessed together. For other terms, see our glossary of orthodontic terms.
Quick questions
Is retrognathia hereditary?
Jaw size and position are largely influenced by heredity; habits such as mouth breathing can also affect development.
Can prognathism only be corrected with surgery?
In growing children, orthodontic appliances may be tried; in people who have finished growing, surgery may be considered for severe skeletal cases.
What is the difference between overjet and overbite?
Overjet describes the horizontal overlap, overbite the vertical overlap.
How do you find out what suits you?
The information here is general; the right plan for you is determined by an intraoral examination, X-rays and a clinician's assessment. At our clinic in Oran, Çankaya, Ankara, we go through these topics together with your questions during the first orthodontic consultation. For a general list of orthodontic problems, you can also see our page on orthodontic problems and treatment options.
