What is the anatomy of the lips?
The lips are the fleshy parts surrounding the oral cavity that is made of only three to five layers of skin, where as the rest of the face can consist of up to 16 layers of skin. The very thin skin combined with a vast network of blood capillaries and nerve endings make the lips very sensitive to tactile perceptions. Besides that, the lower amounts of melanin (pigment cells) also gives a somewhat rosy hue to the lips. The shape and size of lips are greatly influenced by one’s genetics, lifestyle behaviors, and will vary with age.
The lips have always been decorated throughout human history for social status, cultural practices, courtship, beauty, and aesthetic purposes. The lips are important not only as one of the vital aesthetic units of the face but also as a critical tool for speech articulation and for swallowing food. Hence, lip augmentation or enhancement procedures must be highly successful to maintain the normal function of the lips.
Research studies conducted in the late 20th century examine the profiles of a group of Caucasian females and found that fuller and more anteriorly positioned lips were trendier and more aesthetically pleasing. A research study conducted by Nguyen and Turley for about 65 years, beginning in 1930, found that there were significant changes in the ideal lip aesthetics for male model, which included increasing vermilion display, increasing lip protrusion, and increasing lip curl.
The observations above were made by carefully examining and analyzing the progressive changes of male model profiles from photographs collected from famous fashion magazines. Nowadays, thanks to the innovation in the treatments available, and the ever-changing cultural and beauty trends, lip augmentation procedures are gaining interest among patients. In fact, lip augmentation is one of the most common and widely requested aesthetic treatment since the introduction of modern soft tissue implants.
What are the characteristics of the ideal lips?
The ideal aesthetic characteristics and standards of beauty vary greatly across cultures and eras. For example, the Western community prefers plump and well-defined lips. Though models with soft and plump lips were admired and there was indeed a cultural preference for plump lips, the early years of medical aesthetics did not even have precise guidelines for the assessment and enhancement of the lips. Fortunately, extensive research found that the “ideal” lips should have the following characteristics:
- Volume and fullness;
- Correct ratio between the upper and lower lips;
- Well-defined vermilion border.
It is important that the lips maintain a harmonious balance with the other facial features of the patient. A patient with small and delicate facial features with very full lips may not appear aesthetically pleasing since the lips are out of proportion with the rest of the features. Besides the proportion of facial features, lip augmentation procedures can only achieve successful and desirable results when the sexual dimorphism aspect is considered. This is because men are predisposed to having a larger lip volume, total lip height, and mouth width than women.
Recently, the procedural techniques for augmentation and improvement of the lips have greatly progressed due to innovation and availability of countless soft tissue implants on the market.
To ensure the best outcomes for their patients. Physicians must be knowledgeable and familiar with the anatomy and terminology of the lips and the necessary assessments required before they even perform a lip augmentation procedure.
How are the lips assessed prior to lip rejuvenation procedures?
Physicians are greatly encouraged to assess their patients in their natural sitting position because this is a standardized and reproducible position for upright examination. Besides that, it is imperative that the lips are examined while relaxed as well as animated, so as to assess the natural position of the lips and the symmetry of muscle contractions; this can help detect any abnormal asymmetry. The assessment of the lips in these two states can also help to determine the action and hyperactivity of muscles. Though the position of the lips is associated with the teeth and alveolar process, there are actually other factors that also play a role in an attractive smile. Physicians, especially dental professionals, should take the time to thoroughly examine the other anatomical factors that influence the lower face and the smile aesthetics. These factors include the following:
The dentition, gingivae, and alveolar bone components:
- Crown width
- Crown length
- Incisor crown angulation
- Incisal plane
- Open gingival embrasure
- Gingiva-to-lip distance
- Gingival margin
- The relative position of the mandible to the maxilla
Soft tissue components:
- Morphology of the lips and soft tissue
- Prominence of the chin and the nose
Besides the factors above, medical practitioners must also perform a systematic clinical evaluation of the lips to better understand the aesthetic issues at hand and the appropriate treatment required for a successful procedure. The following lip parameters may be evaluated during the initial assessment:
- The height of both upper and lower lips
- The height of lower lip-chin
- The ratio of the upper lip to lower lip-chin height
- The height of both upper and lower lip vermilion
- Interlabial gaps, which are the gaps between the lips at rest
This lip parameter is influenced by the patient’s ethnicity and is directly related with lip prominence. Compared to fuller lips, thinner lips tend to easily follow the movements of the jaw and the teeth. Hence, patients with thin lips may develop obvious aesthetic imperfections caused by the loss or movement of teeth.
This parameter of the lips can be assessed by checking the patient’s side profile to see lip protrusion and prominence relative to the protrusion of the nose and the chin. Lip prominence can vary greatly because of soft tissue factors, including lip thickness; skeletal factors; and dentoalveolar factors, such as the position of the incisor teeth.
Physicians can determine the lip curvature, lip inclination, and lip curl by examining the patient’s frontal and profile views. The position and strength of the dentoskeletal support of the lips can either result in an exaggerated or reduced lip curl. For instance, the maxillary dentoalveolar retrusion could be the cause of a flat upper lip.
Medical professionals should examine the lip posture and lip seal while the patient rests their head in the natural repose position. It is important that both of these parameters be inspected when the patient is relaxed and not exerting any excessive muscle contractions. While each patient has a distinctive orolabial soft tissue posture, physicians must use adaptive postures if the lip seal does not happen in the repose position. This simply means that the patients will experience continuous contraction of circumoral musculature.
The dentoalveolar provides strong support to the lips, so the inclination of the lips indicates the extent and strength of the underlying dentoalveolar. Patients develop protrusion or retrusion of the lips if the upper or lower incisors are either protruding or retruded. Eversion of the lower lip can happen when the upper incisor teeth impinge on the lower teeth.
Lip activity and function:
It is important that the physicians examine the patient for hypertonic (high muscle tone or hyperactivity) or hypotonic (low muscle tone or underactivity) lips. The hypertonic lower lip may retrocline the lower incisor teeth, resulting in a strap-like appearance of the lower lip. Besides that, a hypertonic upper lip levator muscle can instead give rise to an excessively gummy smile. On the other hand, the hypotonicity of the upper or lower lip can make the lips appear flaccid and overstretched when achieving a lip seal. This condition is prevalent among patients with increased lower-face height.
A complete and thorough assessment of the lip anatomy and the perioral region is vital for determining the treatment goals and methods and the path to a successful lip augmentation procedure. It is imperative that both the physicians and the patients agree on the treatment goals so that patients will be satisfied with the results of the procedure.