The Depressor Anguli Oris (DAO) is a small facial muscle that significantly influences our resting expression. Located on either side of the chin, its primary role is to pull down the corners of the mouth. When the DAO remains chronically tense or overactive, it contributes to a perpetually downturned mouth, often called a “resting frown” or “marionette lines.” Understanding the function of this muscle is the first step toward achieving a more relaxed and neutral facial appearance. This article provides methods for identifying the source of this tension and implementing effective relaxation strategies.
Anatomy and Function of the Depressor Anguli Oris
The Depressor Anguli Oris is a triangular-shaped, paired muscle situated in the lower third of the face. It originates from the oblique line of the mandible (the lower jawbone) near the chin. From this anchor point, the muscle fibers converge upward toward the angle of the mouth.
The DAO inserts into the modiolus, a dense fibromuscular node at the corner of the mouth where several facial muscles intersect. Its action is to depress, or pull down, the angle of the mouth, which is associated with expressions of sadness or displeasure. This downward pull directly opposes the action of muscles like the Zygomaticus Major, which lift the mouth corners into a smile.
Persistent tension of the DAO creates a downward drag on the skin, contributing to the formation of lines that run from the corners of the mouth down to the jawline. This muscular imbalance, where depressor muscles overpower the elevators, is why relaxing the DAO can significantly alter the resting face. The muscle is innervated by the marginal mandibular branch of the facial nerve.
Common Causes of DAO Muscle Tension
DAO tension frequently stems from chronic habits and underlying physical imbalances. Repetitive facial movements, particularly habitual frowning or grimacing, lead to hypertrophy (overdevelopment) of the muscle fibers. This overactivity causes the muscle to maintain a shortened, tense state even when the face is at rest.
Chronic stress is a significant contributor, as many individuals unconsciously hold tension in their lower face and jaw. This sustained, low-level muscle contraction is often linked to anxiety or concentration, causing the jaw to be subtly clenched throughout the day. Over time, this constant tension shortens and tightens the DAO, reinforcing the downturned mouth appearance.
Issues with dental occlusion (the way the upper and lower teeth meet) can influence tension in the facial muscles. The entire stomatognathic system, which includes the jaw, teeth, and associated musculature, is interconnected with head and neck posture. For example, a forward head posture, common when looking at screens, strains the neck and jaw muscles, indirectly contributing to tightness in the depressor muscles of the lower face.
Self-Care Techniques for Relaxation
Targeted self-massage is a direct and effective way to encourage the DAO muscle to release tension. To begin, locate the muscle by placing your index and middle fingers on the corner of your mouth and drawing a line down to the jawline, just above the bone. This triangular area is where the DAO is situated.
Apply gentle, sustained pressure to this area with your fingertips, moving in small, circular motions along the muscle’s path for 30 to 60 seconds on each side. An advanced technique involves inserting a clean finger pad just inside the mouth near the corner and applying pressure outward toward the muscle attachment on the lower jaw. This internal approach, called intra-oral massage, targets deeper tension points and helps soften the muscle fibers where they anchor to the bone.
Specific stretches can help elongate the muscle and retrain facial expression patterns. A simple technique is to fold your lower lip over your bottom teeth, consciously pulling the skin down and slightly out to stretch the DAO. Another exercise involves placing your index fingers just above the jawline and gently pulling the corners of your mouth down and away from the midline, holding the stretch for five seconds.
Conscious awareness is important for long-term relief. Throughout the day, check your facial posture, particularly during times of concentration or stress. If you notice your jaw clenching or your mouth corners pulling down, make a deliberate effort to soften your expression and gently separate your upper and lower teeth. This practice of monitoring and interrupting habitual tension patterns helps prevent the DAO from becoming chronically hyperactive.
When to Seek Professional Intervention
When self-care methods do not provide sufficient relief for chronic or severe DAO muscle tension, professional intervention offers more intensive solutions. A common medical approach involves the use of neuromodulators, such as botulinum toxin, precisely injected into the DAO muscle. The neurotoxin temporarily blocks the nerve signals that cause the muscle to contract, preventing the downward pull on the mouth corners.
This temporary relaxation allows the mouth-lifting muscles to exert more influence, which can elevate the resting position of the mouth. The effects typically last between three and four months, requiring repeat treatments to maintain the relaxed state. Because the lower face is a complex area, these injections must be performed by an experienced medical professional to avoid affecting surrounding muscles involved in speech or eating.
Physical therapy or specialized facial acupuncture can address deep-seated muscular imbalances. A physical therapist can provide advanced manual release techniques and a specific program to strengthen the antagonistic muscles that lift the mouth, retraining the lower facial structure. If tension is related to jaw alignment or teeth grinding, a consultation with a dentist or orthodontist is appropriate. They can assess for underlying bite issues or temporomandibular joint dysfunction contributing to the chronic facial muscle strain.