W hat are the aesthetics of ideal lips in men and women? The lips form a transition zone between the facial skin and the oral mucosa and are a significant aesthetic feature of the face. The lips are perhaps the most movable expressive aesthetic unit of the face. Leonardo da Vinci described the importance of the ‘strongly movable section of the face around the mouth and chin in determining facial expression’, which emphasizes the importance of observing the face in animation as well as in the static state.
“Eternity was in our lips and eyes.”
William Shakespeare
Anatomy of the Lips
1. Philtrum
2. Philtral ridges/columns
3. Cupidʼs bow
4. High points of the vermilion (bilateral)
5. White roll
6. Upper lip vermilion
7. Upper lip tubercle
8. Vermilion border (mucocutaneous junction)
9. Lower lip vermilion
10. Oral (labial) commissures
11. Nasolabial groove
12. Mentolabial groove
Aging
Lip size tends to increase until puberty, due to muscular and glandular hypertrophy, following which it begins to decrease due to changes in the skin and the supporting tissues.
Lip Lines
They are defined as the vertical position of the upper and lower lips in relation to the anterior dentition. The ‘ideal’ dentolabial relationship results when the upper lip covers approximately the upper two-thirds of the maxillary incisor crowns at rest, with 2–4 mm maxillary incisor exposure.
There are high and low lip lines.
Lip Tonicity
It refers to the muscular tone of the lips, related to the production of normal muscular contraction and function.
Hypertonicity refers to a state of abnormally high muscle tone, sometimes described as hyperactivity or overactivity, which is common in Class II, division 2 malocclusion.
Hypotonicity of the upper lip is common in patients with increased lower face height.
Lip Morphology or Form and Structure of Ideal Lips
Lip Height:
The ratio between the upper and lower lip subdivision should be 1:2 (upper lip: 1/3, lower lip: 2/3).
Lip Incompetence:
With the mandible in rest position and the lips in repose, the interlabial gap may be between 0 and 3 mm. An interlabial gap of greater than 4 mm is usually an indication of an incomplete lip seal.
Variation in Vermilion Heights:
1:1 ratio is preferable.
Upper Lip Thickness:
This may be measured horizontally from a point on the anterior aspect of the maxillary alveolar process.
Lip Contour:
It may be evaluated in frontal and profile view. In frontal view, the lips are evaluated for curvature. In the profile view, the lips are evaluated for lip curl (anterior curvature) and inclination (sagittal cant).
Ethnic Variation:
Lip thickness is influenced to a great extent by ethnic background. Caucasians of northern European backgrounds have relatively thin lips compared with Caucasians of eastern European or Middle Eastern origin. Black individuals often have the greatest degree of lip thickness, coupled with an increased propensity for the dentoalveolar protrusion, leading to an overall more bilabial protrusive appearance.
Complete Lip Seal (Lip Competence):
Competent lip posture implies adequate lip seal, with the lips able to contact one another without strain when the mandible is in rest position.
Incomplete Lip Seal (Lip Incompetence):
Incompetent lip posture occurs when the lips are unable to form an adequate seal under similar unstrained conditions, i.e. excessive separation of the lips at rest.
Proffit has stated that as a general guideline, which holds for all ethnic groups, lip separation at rest should be no more than 3 – 4 mm; above this, the lips are termed incompetent.
Lip Prominence:
E – line (Ricketts ): Upper and lower lip prominence may be measured in relation to the ‘Esthetic’ (nose – chin) line, drawn from pronase to soft tissue pogonion. This measurement is highly dependent on nasal tip and chin projection.
In white Caucasians the average values are:
Upper lip: − 4 to − 6 mm behind E – line
Lower lip: − 2 to − 4 mm behind the E – line.
Influence of Sex:
Slightly greater relative lip prominence in women is partly due to reduced nasal projection.
Influences of Ethnicity:
Black individuals tend to have more prominent lips, due to greater soft tissue lip thickness and a tendency to bimaxillary dentoalveolar protrusion.
Position of the Lower Lip in Relation to the Upper Lip:
As a general guideline, the lower lip should rest slightly posterior to the upper lip in profile view.
Width of the lips in relation to the jaw:
Ideally, the width of the lips should be 40% of the jaw width.
