Cosmetic Effects of Botulinum Toxin in the Upper Lip, DAO, and Mentalis
Botulinum toxin injections in the upper lip, depressor anguli oris (DAO), and mentalis muscles produce specific aesthetic improvements by temporarily paralyzing these muscles, resulting in reduced perioral wrinkles, elevated mouth corners, and smoothing of chin dimpling.
Mechanism of Action
Botulinum toxin type A blocks acetylcholine release at the neuromuscular junction, causing temporary muscle paralysis that lasts weeks to months 1, 2. This reversible paralysis of targeted facial muscles reduces dynamic wrinkles and modifies facial contours 3.
Specific Treatment Areas and Effects
Upper Lip (Perioral Region)
- Reduces vertical lip lines ("smoker's lines" or perioral rhytids) by weakening the orbicularis oris muscle 4
- Softens the appearance of a gummy smile when injected into the levator labii superioris, reducing excessive gingival display 5
- Prevents downward nasal tip sagging through strategic injection points 5
- Treatment of the perioral area is now routinely performed and contributes to overall facial aesthetic improvement 4
Depressor Anguli Oris (DAO)
- Elevates the corners of the mouth by weakening the downward pull of the DAO muscle 4
- Reduces marionette lines (lines extending from mouth corners downward) 5
- Creates a more pleasant, less sad facial expression by preventing the downturned mouth appearance 6
- The DAO is a key muscle for addressing lower facial aesthetics 4
Mentalis Muscle
- Smooths chin dimpling and "pebbled chin" appearance caused by mentalis hyperactivity 6, 5
- Reduces the appearance of a dimpled chin that occurs with certain facial expressions 6
- Approximately 30.5% of patients in full-face treatment protocols receive mentalis injections 5
Clinical Considerations and Safety
Dosing and Technique
- Full-face treatment protocols typically use 113.8 ± 17.6 units total of onabotulinumtoxinA across multiple facial areas 5
- Individualized dosing per injection site varies by muscle size, strength, and desired effect 6
- Men generally require higher doses than women due to greater muscle mass 4
Common Pitfalls
- Unwanted diffusion from mentalis to depressor labii inferioris can occur, causing asymmetric lower lip movement 5
- This complication occurred in 5 of 189 patients (2.6%) in one large series, but all cases were minor and self-limited 5
- Proper injection technique and anatomical knowledge are essential to avoid diffusion to adjacent muscles 6
Safety Profile
- These lower facial treatments are safe when performed correctly, with complication rates around 3.2% in full-face protocols 5
- All reported complications were minor and temporary, resolving without intervention 5
- The treatment has been confirmed as effective and safe in both short and long-term use 6
Treatment Integration
- Combination therapy using botulinum toxin with fillers or lasers produces optimal aesthetic results 4
- Full-face approaches that include upper lip, DAO, and mentalis treatment are increasingly prevalent and lead to excellent overall outcomes 5
- Treatment of these advanced facial areas requires greater anatomical understanding compared to traditional upper face injections 4