(y) ANTERIOR FACE HEIGHT
* UAFH: Upper Anterior Face Height
Linear measurement from Nasion to Anterior Nasal Spine (N-ANS).
* LAFH: Lower Anterior Face Height
Linear measurement from Anterior Nasal Spine to Menton (ANS-Me).
* UAFH / LAFH Ratio:
The ratio of UAFH to LAFH is more important than the individual linear measurements of UAFH and LAFH. UAFH varies with the superior-inferior dimension of the size of an adult skull while the ratio of UAFH/LAFH indicates the balance of facial proportions.
• UAFH/LAFH ratio <0.8 indicates a greater LAFH, or longer lower anterior face height.
• UAFH/LAFH ratio >0.8 indicates a smaller LAFH, or shorter lower anterior face height.
(y) CHIN
* Pg – NB: Pogonion to Nasion – B point (3 mm +/- 2 mm)
Reference Line: Nasion – B point
The prominence of the bony chin (not to be confused with the soft tissue chin) is measured by the distance of Pogonion (the most anterior point of the chin) to the reference NB line.
A smaller than average value indicates a recessive chin while a greater than average indicates a prominent chin.
Chin prominence is also affected by auto-rotation of the mandible (hinge axis rotation at Centric Relation). Rotation of the mandible in an anterior-superior direction (forward) increases chin prominence relative to NB. Rotation of the mandible in an inferior-posterior direction (backward) decreases chin prominence relative to NB.
SN-Pg and NPg-FH also measure chin prominence with respect to SN and FH reference planes.
