Extra-oral examination: soft tissues
As well as the skeletal pattern, the facial soft tissues can influence tooth position. If there is an underlying skeletal discrepancy, the soft tissues may help to guide teeth into a more favourable position (dentoalveolar compensation) so that the occlusal relationship is improved. Soft tissue evaluation should involve examination of:
The following aspects of the lips should be examined:
- lip fullness and nasolabial angle;
- lip tone;
- lower lip line;
- lip competency;
- method of achieving an anterior oral seal at rest/swallowing.
Lip fullness maybe classified as protrusive, straight or retrusive. The relationship of the lips to Ricketts Esthetic line (E-line), which runs between the tip of the nose and chin point, can help with this assessment (Figure 15.1A). If the lower lip lies anterior to the line it is considered protrusive, if it lies 0–2 mm behind it is normal and if >2 mm posterior to the line it is retrusive. If the nose is large, so that the E-line is displaced anteriorly, this may give a misleading assessment. The lips tend to become less protrusive with growth as the nose and chin point develop (see Chapter 6).
The nasolabial angle (NLA), formed by a tangent to the upper lip and columella of the nose, can give an indication of upper lip position (Figure 15.1B). In Caucasians, the upper lip should slope/>