What is the recommended treatment approach for a healthy adult patient with no significant medical history seeking botulinum toxin (Botox) injections for the upper lip, mentalis, and depressor anguli oris (DAO) muscles?

Botulinum Toxin Treatment for Upper Lip, Mentalis, and DAO

For cosmetic treatment of the upper lip, mentalis, and depressor anguli oris (DAO) muscles in healthy adults, botulinum toxin injections are safe and effective when performed with precise anatomical technique, using conservative dosing (typically 2-4 units per muscle group in the lower face) and avoiding medial injection points to prevent smile asymmetry and lower lip dysfunction. 1, 2, 3

Treatment Approach by Muscle Group

Depressor Anguli Oris (DAO)

• Inject laterally along the muscle belly, avoiding the medial border where the DAO overlaps with the depressor labii inferioris 2
• The lateral border is adjacent to risorius, zygomaticus major, and platysma muscles, requiring precise localization 2
• Use external facial landmarks to identify optimal injection sites rather than relying solely on palpation 2
• Medial injection or toxin diffusion into the DAO can cause contralateral depressor labii inferioris hyperfunction, resulting in asymmetric smile with excessive lowering of the opposite lower lip 4

Mentalis Muscle

• Base injection sites on mandibular external anatomical landmarks to ensure proper localization 1
• The mentalis originates from the alveolar bone of the mandible and is the primary target for treating cobblestone chin from hyperactivity 1
• Avoid deep or lateral injection to prevent mouth closure insufficiency and lower lip ptosis 1
• Understanding mandibular anatomy leads to better injection localization and outcomes 1

Upper Lip (Orbicularis Oris)

• The orbicularis oris is now routinely treated for overall facial appearance improvement 3
• Use minimal units in this area due to the risk of functional impairment 3
• Precise technique is essential given the anatomical complexity of the lower face 4

Dosing Considerations

• Lower face typically requires 20 units total distributed across multiple injection points 4
• Individual muscle groups require 2-4 units to minimize adverse events while maintaining efficacy 2
• Men require more units than women for equivalent effect 3
• Conservative dosing reduces complications in patients with severe rhytids, previous facial surgery, or altered anatomy 5

Critical Safety Principles

Injection Technique

• Adjust dose, distribution, and timing to minimize adverse event frequency 6
• Use proper injection techniques and appropriate regional dosing 5
• Light touch massage poses less risk than deep tissue manipulation 6
• Avoid aggressive myofascial release techniques for 2 weeks post-injection to prevent toxin migration 6

Adverse Event Management

• All effects are temporary and reversible, typically lasting 3-6 months 6
• The primary risk involves toxin diffusion from target muscles to adjacent structures (FDA boxed warning) 6
• Smile asymmetry from unintended muscle paralysis can be corrected with additional 3-unit injection into the hyperactive contralateral muscle 4
• Complications are more likely in patients with severe rhytids requiring higher doses, previous facial surgery with altered anatomy, or preexisting neuromuscular disease 5

Common Pitfalls to Avoid

• Medial injection into DAO causes depressor labii inferioris dysfunction and smile asymmetry 4
• Excessive dosing increases risk of mouth closure insufficiency and lip ptosis 1
• Inadequate anatomical knowledge leads to injection into adjacent muscles 2
• Deep tissue massage within 2 weeks may displace toxin to unintended areas 6

Combination Therapy

• Botulinum toxin combined with lasers or filler substances provides ideal aesthetic outcomes 3
• Multiple areas of the upper face can be treated simultaneously to increase patient satisfaction 3