Botulinum toxin for the depressor anguli oris
Botulinum toxin in the depressor anguli oris is used to soften the droop of the mouth corner when that droop has a muscular component. It is what patients look for as "Botox in the mouth corner". In many cases, however, the downturned mouth comes mainly from loss of support, and the right answer is different, or a combination.
This guide is a review. It does not give doses, points or injection technique, which are the decision of the qualified professional, according to the product label and the rules of their professional council. The detailed anatomy of the muscle is in the glossary entry for the depressor anguli oris; the area as a whole is in mouth corners.
Why does the mouth corner droop?
The position of the commissure is the result of a balance. Pulling up are the zygomaticus major, the levator anguli oris and the risorius; pulling down are the depressor anguli oris and the platysma. They all meet at the modiolus, the fibromuscular knot lateral to the commissure.
Other factors act on this balance:
- Loss of volume and support in the lower third, around the commissure and in the chin.
- Descent of the cheek tissues, which weighs on the area and forms the marionette line.
- Hyperactivity of the depressor, which pulls the corner down when speaking and in expressions.
- Anatomy and habit, which explain a downturned corner in young patients.
The toxin acts only on the third item. That is why the central question of the assessment is: how much of the droop is muscle and how much is structure?
Toxin, filler or both?
| Finding on assessment | Predominant component | Most coherent option |
|---|---|---|
| Corner drops when speaking or in expressions, nearly normal at rest | Muscular | Toxin in the depressor |
| Corner drooping at rest, with no major change in expression | Volume and support | Mouth corner filler |
| Marionette line that continues to the jaw | Lower third support | Filler with jaw and chin in the plan |
| Corner drooping at rest and worse with expression | Mixed | Combination, in stages |
| Retruded chin that wrinkles when speaking | Hyperactive mentalis and lack of projection | Mentalis toxin and chin filler |
| Significant lower third laxity | Skin and tissues | Firming options or referral; the toxin has little role |
How to assess before recommending treatment?
- Rest. Compare the height of the commissures with the line where the lips meet. Record whether there is a difference between sides.
- Speech and a look of displeasure. Watch whether the corner drops markedly and whether a crease appears running down from the commissure toward the jaw.
- Smile. Assess symmetry and how far the lower lip drops to show the teeth. That movement depends on the depressor labii inferioris, a neighbor of the depressor anguli oris and partly covered by it.
- Palpation during contraction. Ask the patient to pull the corners of the mouth down and palpate the muscle mass over the jaw.
- Chin and neck. The mentalis and the platysma often work together in pulling the lower third. Sometimes the plan includes all three areas; the neck part is in toxin for platysmal bands.
- Oral function. Ask about difficulty holding liquids, whistling or pronouncing certain letters. Professions that depend on the mouth (wind instrument players, singers, teachers, broadcasters) call for a specific conversation.
What are the risks and unwanted effects?
The depressor anguli oris is small and surrounded by muscles with important functions. The margin for error is narrow.
| Effect | Probable cause | How it usually evolves |
|---|---|---|
| Asymmetric smile | Reach of the depressor labii inferioris | Temporary; the lower lip drops less on one side |
| Difficulty holding liquids or articulating words | Reach of the orbicularis oris | Temporary; quite bothersome in daily life |
| Change in lower lip position | Reach of the mentalis or other depressors | Temporary |
| Small effect | Predominant structural component | Reassess the plan |
| Asymmetry between sides | Different muscle strength, different response | Assess at follow-up |
| Bruising and local pain | Vessels of the area | Resolves in days |
An asymmetric smile after toxin is the complication patients remember most, because it shows in every conversation and every photo. It is usually transient, but may last as long as the product's action.
The overview of toxin complications, by area, is in complications with botulinum toxin, and the map of agonists and antagonists is in facial muscles in botulinum toxin.
What is the expected timeline?
| Moment | What usually happens |
|---|---|
| First days | Little visible change |
| First weeks | The corner drops less when speaking and in expressions |
| Following weeks | Stable effect; time to assess smile symmetry |
| A few months | The effect fades and the pull returns gradually |
General timeframes are in how long the toxin takes to work and how long Botox lasts. Because the area is small and functional, the conservative approach, with reassessment before any add-on, is usually the safest.
How to combine it with filler?
When both components exist, the order and interval are the professional's decision. Some lines of reasoning that help with planning:
- Treating the structure usually provides the base. Without support, reducing the strength of the depressor changes the resting position little.
- The toxin refines the expression. It acts on the corner that drops when speaking, something filler does not solve.
- One step at a time makes it easier to read. By doing them at different times, you and the patient know what each option contributed and what to correct.
- With hyaluronic acid in the area, hyaluronidase should be available. The facial artery and the origin of the labial arteries pass close to the commissure; see labial vascular occlusion.
To structure the plan and the conversation about prices in stages, see staged plan.
How to explain it to the patient?
Patients often say "my mouth is downturned" or "I look angry". Show in the mirror what happens when they speak and when they are at rest.
Record the assessment, the video and the guidance in the patient record, and use an informed consent that mentions asymmetric smile and changes in lip function. A template is at informed consent for botulinum toxin.
And in Harmy?
Checklist for toxin in the depressor anguli oris
- Muscular component confirmed: the corner drops when speaking and in expressions.
- Volume and support component assessed, with chin and jaw.
- Smile and speech recorded on video before the injection.
- Oral function and the patient's profession considered.
- Indication checked against the label of the product registered with ANVISA.
- Patient informed about asymmetric smile and changes in the lips.
- Follow-up scheduled to assess symmetry before any add-on.
Frequently asked questions
Does Botox in the mouth corner lift a downturned mouth?
It can soften the droop when it comes from the strength of the depressor anguli oris muscle. When the main cause is volume loss, laxity or lack of chin support, the toxin alone usually adds little, and the plan includes other options.
What is the difference between Botox and filler at the mouth corner?
The toxin reduces the strength of the muscle that pulls the corner down. Hyaluronic acid filler restores support and volume to the corner of the mouth and the marionette line area. Many patients have both components, and the options can be combined.
Can Botox in the mouth corner leave the smile crooked?
It can, if the toxin reaches the depressor labii inferioris or the orbicularis oris. The smile becomes asymmetric or the lower lip loses part of its movement. It is usually temporary, and the risk is lower with proper assessment and technique.
How long does Botox last in the mouth corner?
Generally a few months, as in other areas of the face, varying with the product, the dose, the strength of the muscle and the patient. The effect fades gradually.
Harmy images are illustrative simulations generated by AI from the patient's photo to support the conversation between practitioner and patient. They are not a promise of results. Indication, technique, product and volume are solely the decision of the licensed practitioner. This content is for information only and does not replace a clinical assessment.