Analysing chin prominence in relation to the lower lip: The lower lip-chin prominence angle.

The purpose of this investigation is to describe a potentially useful analysis in assessing the required extent of sagittal chin augmentation or set-back, by relating chin prominence to lower lip position using the 'lower lip-chin prominence angle'. The secondary aim was to quantitatively evaluate the influence of this angle on perceived attractiveness and desire for surgery. Having described this angular analysis, a quantitative evaluation was undertaken by incrementally altering the angle on an idealised profile image to create a range of images that were rated on a 7-point Likert scale by a pre-selected group of pre-treatment orthognathic patients, clinicians and laypeople. In treatment planning alterations in chin prominence, an 'ideal' sagittal position with soft tissue pogonion on or just behind a true vertical line through the most prominent point of the lower lip may be used. Chin retrusion or prominence up to an angle of 15° retrusion to -5° prominence is deemed acceptable. Surgery is desired from chin prominence of greater than -15° and retrusions greater than 25°. The greater the retrusion or prominence of the chin from an angle of 0°, the less the perceived attractiveness and the greater the desire for surgical correction.