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A to Z of Lip Augmentation: Anatomy and Aesthetics

In recent years, the pursuit of youth and beauty has led to a surge in cosmetic surgeries, with lip augmentation becoming increasingly popular.

Fortunately, advancements in techniques and materials have made it possible to alter the appearance of the lips through various injectable substances and surgical methods. The goal is to create a balanced and aesthetically pleasing form that complements an individual's unique facial features and ethnic background. Additionally, it is essential to consider the natural aging process, as the properties of the lips change over time, including volume loss, thinning, and lengthening of the upper lip. Therefore, understanding lip anatomy and physiology in the context of facial aging is vital for obtaining optimal cosmetic results.

In this blog, we will discuss the importance of lip anatomy and how it should be examined, the natural aging process of the lips and the various non-surgical options for lip augmentation.

Lip Anatomy

The lip anatomy can be categorised into external components: skin and mucosa.

The skin of the lip follows relaxed skin tension lines and extends from subnasale to the vermilion border, transitioning to the mucosa. The vermilion border, also known as the junction between the skin and mucosa, is a significant anatomical landmark for lip augmentation procedures, particularly injection-based techniques.

The mucosa consists of both dry (exposed to air) and wet (inner surface) portions. The vermillion, which lacks keratin and contains a rich vascular network, gives the lips their characteristic red color. Beneath the visible surface lies the orbicularis oris muscle, which provides tissue volume and maintains oral competence. Innervated by the facial nerve and sensory branches of the trigeminal nerve, the muscle is supplied with arterial blood from the labial artery, a branch of the facial artery.

The lips serve two main functions. Firstly, they act as a sphincter, thanks to the orbicularis musculature. The lower lip, less mobile, helps maintain oral competence, while the upper lip, more mobile, drapes over the upper dentition. Secondly, the lips play a crucial role in facial expression, facilitating communication through speech, smiling, laughing, and other expressions.

Lip Aesthetics

When evaluating lip aesthetics, it is crucial to consider the overall facial appearance. The lips should be in harmony with the surrounding soft tissue and skeletal structures of the midface, taking into account each individual's unique features. Excessive lip augmentation in individuals with underdeveloped midfaces can result in an unnatural appearance.

Facial analysis often divides the face into subunits. Within the upper lip, there are three subunits: the central philtrum and two lateral subunits. The lower lip consists of a single subunit. The face is also divided into horizontal thirds, with the lips located within the lower third. The lower lip is approximately twice the height of the upper lip.

See below the figure illustrating facial analysis, using horizontal thirds. (From Votto et al, 2021)

Horizontal thirds, facial analysis, lip augmentation

The concept of the golden ratio, commonly used in various disciplines, including art and mathematics, has been applied to describe the ideal proportions of the lips relative to the rest of the face. In youthful individuals, the vertical height ratio between the upper and lower lips is ideally 1:1.5. The upper lip is particularly notable for its Cupid's bow complex, characterized by two high points of the vermilion and a sloping depression between them in the central lip. Preserving these delicate contours is important during lip augmentation to avoid an unnatural appearance.

See below the figure illustrating the use of golden ratio in facial analysis. (From Votto et al, 2021)

Golden ratio, facial analysis, Cupid's bow complex

When assessing lip aesthetics, the profile view and lip projection should be considered. The upper lip should project 3.5 mm anterior to a line drawn from subnasale to pogonion, while the lower lip should project 2.2 mm anterior to that line. Most experts agree that the upper lip should have greater projection than the lower lip.

The underlying dentoalveolar structures, including the dentition and alveolar ridges, play a role in lip projection. It is important to consider natural tooth display in women and men when performing lip augmentation. Women typically show 3-4 mm of their anterior teeth when the lips are at rest, and these standards should be preserved during augmentation. Orthodontic treatment may be beneficial in addressing lip augmentation camouflage.

Aging Process of Lips

The aging face presents various changes, particularly in the lips. These changes can be attributed to both intrinsic and extrinsic factors, such as genetics, social factors, sunlight exposure, and smoking. Intrinsic changes primarily occur in the dermis, where there is a decrease in ground substance and a shift in the ratio of collagen types. Elastic fibers become thin and fragmented, leading to a reduction in collagen. Extrinsic factors like sun damage and smoking can accelerate this process. The aging process begins with a phase of glandular and muscular hypertrophy, resulting in full, youthful lips. However, the most noticeable sign of aging is the loss of ideal fullness and projection of the lips.

As the aging process continues, additional changes occur:

  1. Skin laxity increases, causing the corners of the mouth to turn downward.

  2. Muscles, subcutaneous fat, and even the structures supporting the teeth and gums lose volume with age.

  3. Visually, the aging lip shows a decrease in the amount of vermillion, a less defined Cupid's bow, and a less prominent white roll (the border between the lip and surrounding skin).

  4. The repetitive movement of the orbicularis muscle can lead to vertical lines on the upper and lower lips, known as vertical rhytids.

  5. Over time, marionette lines may also form, characterized by vertical lines at the corners of the mouth, giving an appearance of sadness.

Non-surgical Procedures for Lip Augmentation

There are various non-surgical options available for lip enhancement. Surgical implants and autologous fat transfer are less commonly used today. The most popular nonsurgical method is the injection of dermal fillers, which can increase lip volume and shape. There is ongoing debate about the ideal filler material for lip augmentation, with a variety of natural and synthetic compounds being used, each with their own advantages and limitations.

Dermal fillers, particularly those derived from hyaluronic acid (HA), dominate the market, constituting about 77% of market shares. Temporary biodegradable fillers derived from bovine collagen, human collagen, and porcine collagen are also available. Implants made from acellular human dermis and allogeneic human tissue collagen matrix have shown promise. Other options include neurotoxins, lasers, micropigmentation, and autologous fat grafting, although the long-term effectiveness of fat grafting is debated. In addition to fillers, surgical lip implants, Botox, and various skin resurfacing techniques can be used as adjunctive therapies for lip enhancement.

Autologous Fat Injection

The use of fat injection for transplanting free fat grafts has been established since the introduction of liposuction. The technique was first attempted in 1893 for facial deformity treatment and has since been widely used for various facial tissue repairs. A core fat graft technique was developed specifically for lip augmentation and correcting deficiencies in the cheeks and buccal area. Alternatively, the microlipoinjection technique can be used to harvest fat from donor sites such as the groin, gluteal fold, and lateral gluteal area. The harvested fat cells are purified and then injected into the subcutaneous areas requiring volume enhancement.

To ensure successful fat grafting, it is important to select a donor site that can be concealed cosmetically, properly prepare the fat graft, and securely place it into the recipient site with careful control of bleeding. Overcorrection of approximately 30% to 50% is necessary due to the rapid resorption of the graft, which can lead to variable survival rates ranging from 40% to 80%. While fat injection can be beneficial in perioral regions, its limited longevity and potential for irregular surface contours have restricted its use in the lips. Currently, it is mostly used as an adjunctive therapy for lip augmentation.

Collagen Fillers

Collagen has been used as a filler in aesthetic procedures for over two decades and was one of the first fillers introduced in the field. The initial collagen fillers were derived from bovine collagen, with products like Zyderm and Zyplast entering the market in the early 1980s. In 2003, human-derived collagen obtained from neonatal foreskin, namely CosmoDerm and CosmoPlast, was developed. Unlike bovine collagen fillers, these human-derived products do not require an allergy skin test and were approved for restoring the lip border.

Both Zyplast and CosmoPlast are cross-linked and are used to address moderate to deep lines and enhance the junction between the colored part of the lip (vermillion) and the surrounding skin. However, collagen has fallen out of favor and been overshadowed by newer and more effective filler materials. Many collagen-based fillers have been discontinued due to their limited efficacy. Additionally, collagen fillers have a relatively short duration, typically lasting only around 3 months, compared to hyaluronic acid (HA) fillers, which can last an average of 6 to 12 months.

Hyaluronic Acid

The next group of fillers commonly used is derived from hyaluronic acid (HA), a substance found in the dermis and other tissues in the body. HA fillers have gained popularity due to their effectiveness, biocompatibility, and safety profile. They are also hydrophilic, meaning they attract water from surrounding tissues, further enhancing soft tissue volume. HA fillers do not require a skin test and are easily accessible. Their duration of activity typically ranges from 6 to 12 months.

Nonanimal HA fillers can be cross-linked with other molecules to increase their stability against hyaluronidase, an enzyme that breaks down HA. The cross-linking agent used in biphasic and monophasic HA fillers is 1,4 butanediol diglycidyl ether. Restylane and Perlane are examples of biphasic HA fillers that have been extensively used for lip enhancement. Restylane, approved by the FDA in 2003, is suitable for treating moderate to severe wrinkles and folds.

Juvederm, approved by the FDA in 2004 for correcting nasolabial folds, is another HA-derived filler that is now commonly used for lip augmentation. Juvederm is an example of a monophasic monodensified HA filler, and its effects can last up to 6 to 9 months when injected into the lips. Monophasic HA fillers contain a mixture of HA molecules of varying sizes and shapes. Juvederm, with its Hylacross gel technology, provides a softer and smoother consistency compared to other HA fillers.

Understanding the aging lips and the different filler materials available, including HA fillers, is important for achieving natural results. Injection techniques specific to filler materials and basic guidelines for achieving natural outcomes are described.

See below the figure summarising the common dermal fillers. (From Votto et al, 2021)

Dermal fillers, Restylane, Juvederm, Perlane, Radiesse

Side Effects & Complications

Complications can arise from lip augmentation procedures due to technical errors, allergic reactions, or non-allergic responses to the filler material. Early side effects such as redness, swelling, bruising, and pain at the site are generally treated conservatively with ice, elevation, and over-the-counter medications like nonsteroidal anti-inflammatory drugs.

Common complications include asymmetry and visible irregularities in the contour of the lips. Superficial placement of fillers can result in visible deformities, and if skin blanching occurs, it indicates that the filler has been injected too superficially. Massage can help disperse the filler material to the correct subdermal layer. Granules or dermal nodules may also appear, which can be treated with steroid injections or 5-fluorouracil injections.

Rare complications include intravascular infiltration and skin necrosis, occurring in approximately 0.001% of filler procedures. Intra-arterial injection or occlusion of subdermal arteries by filler material can lead to skin necrosis. The use of a blunt-end cannula can minimize the risk of intravascular injection. If there is suspicion of intravascular injection, the filler treatment should be stopped, and a warm compress can be applied. In cases of excess hyaluronic acid filler or improper dispersion, hyaluronidase can be used to break down the filler material if necessary.


Lip augmentation is a commonly performed elective cosmetic procedure that can be done in the surgeon's office. While it is generally safe, it requires a comprehensive understanding of anatomy, physiology, aesthetics, and techniques to achieve natural-looking and desirable outcomes. Dermal fillers are the most popular and frequently used materials for lip augmentation. There are various injection techniques available, and following anatomical norms and guidelines is crucial to meet patients' expectations and create natural, youthful, and full lips.


Lip Augmentation (2021) Hyaluronic Acid Is an Effective Dermal Filler for Lip Augmentation: A Meta-Analysis (2021)

Current concepts in lip augmentation (2016)


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