Prognathism: a jaw projected forward, what it is
- Nerve
- Highlighted area
Quick facts
- Definition
- Projection of the mandible (mandibular prognathism) or maxilla (maxillary prognathism) ahead of the expected pattern for the face.
- How it is assessed
- In profile, using reference lines and the relationship between the teeth, usually with cephalometry.
- Relationship with occlusion
- Mandibular prognathism usually accompanies Angle class III, with the lower teeth ahead of the upper ones.
- Limit of facial harmonization
- The change is skeletal; facial harmonization can camouflage aspects of the contour but does not correct the bone base.
Prognathism is the projection of a facial structure ahead of what is considered the pattern for that face. The term usually refers to the mandible, but it also applies to the maxilla. When the mandible is the main player, the chin and the base of the lower lip sit ahead of the line of the rest of the face, which is clearly visible in profile.
What are the types?
| Type | Structure involved | How it looks in profile |
|---|---|---|
| Mandibular prognathism | Large or strongly projected mandible | Chin forward, lower lip prominent |
| Maxillary prognathism | Projected maxilla | Midface and upper lip forward |
| Pseudoprognathism | Retruded maxilla (the chin only seems forward) | Normal chin, retruded midface |
The distinction between true and relative is important. In a patient with a retruded maxilla, the mandible may be in a normal position and still look forward. Planning without separating the two cases leads to wrong conclusions.
How is it assessed?
By inspecting the profile and by measurements. Facial analysis uses reference lines, such as the Steiner S line, and the facial convexity angle, which tends to be straight or concave when the mandible is strongly projected. The relationship between the teeth, Angle class III, completes the reading, and cephalometry measures the skeleton on an X-ray.
In the facial harmonization clinic, assessment is visual and comparative. The professional observes the facial profile, identifies the imbalance and decides whether the case fits aesthetic procedures or needs referral to orthodontics and oral and maxillofacial surgery.
What can and cannot facial harmonization do?
Harmonization can work on the harmony of the lower third in mild cases, adjusting the perceived proportion between the lips, the labiomental fold and the chin. In someone with a projected mandible, the goal is usually to balance the whole, not to increase chin projection even further. In someone with retrogenia or micrognathia, the logic is the opposite.
Also called: prognathia, mandibular projection.
Frequently asked questions
Can prognathism be corrected with filler?
No. Prognathism comes from the position of the bones and the occlusion. Filler can change how parts of the contour are perceived, but correcting the base is orthodontic or surgical, indicated after a specialist assessment.