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Orthognathic classification - Retrognathia class II

The word 'retrognathia' is derived from the ancient Greek words retro (backwards) & gnathos (jaw).
Lower jaw too short
Synonym: retrognathia - mandibular retroposition - mandibular retrusion - micrognathism - bird face.
Facial Sculpture Clinic - Dr Joël Defrancq - Jaw surgery and implant reconstructive surgery Orthognathic surgery involves a lower jaw advancement (BSSO Bilateral sagittal split advancement). A chin advancement procedure is often needed as well. The dental classification of a receding lower jaw is a Class II 1&2 and is based on Mr Angle's Classification of malocclusion (Angle Class I - Class II 1 & 2 - Class III).

Mr Angle was a most famous orthodontist from the beginning of the last century. This dental classification is based on antero-posterior (sagittal) dimension and does not take into account the vertical discrepancies (short or long face) or transversal discrepancies (narrow or broad).
There are two types: Angle Class II 1 & 2
Treatment of Angle Class II 2: orthodontically, the condition should be turned first from a Class II 2 into a Class II 1. Only then can orthognathic surgery (BSSO) change it into a normal class I.
Upper jaw prognathism
Synonym: Protruding upper jaw.
Facial Sculpture Clinic - Dr Joël Defrancq - Jaw surgery and implant reconstructive surgery Upper jaw prognathism is exceptionally rare, yet they are nevertheless split up in two groups.

  1. Upper jaw prognathism (Maxillary Hyperplasia).
  2. Alveolar Prognathism (often racial). 

Those two groups should not be confused with the far more common mandibular retrognatia.

True upper jaw prognathism

This means that the upper jaw is oversized in the three axis of space: It is too broad, protruding too far anteriorly, and too long vertically.

Alveolar prognatism

Those patients have only pro-alveolie abnormalities in the front-teeth area. The front teeth jut out horizontally from the face (protruding too far anteriorly), but without vertical consequences. Surgery involves setting the upper jaw back (Le Fort I set back) or orthodontics with premolar extraction, or both, but always with a mandibular advancement!
Postoperative instructions & frequently asked questions

My orthodontist tells me that he can avoid surgery by extracting two premolars in the upper jaw and closing the gaps orthodontically?

Some orthodontists certainly prefer not to send a patient to a maxillofacial surgeon for a lower jaw advancement. And so, they choose to extract two premolars in the upper jaw and retract the front orthodontically. This creates flat faces and virtually always compromises the facial aesthetics outcome.
The bottom line in a skeletal Class II 1 is always an excessively small lower jaw, not an excessively large upper jaw with too many teeth (or only in very exceptional cases). Please remember that the bottom line is bone, not teeth.