The masseter is the most powerful jaw closing muscle, generating bite forces of 700-800 N at the molar teeth. Its hypertrophy from bruxism produces the square jaw appearance of masseter hypertrophy. Masseter nerve transfer to the facial nerve is the most popular reinnervation technique for facial palsy reconstruction — providing bite-activated smile with minimal donor deficit.
| Origin | Superficial part: lower border of the zygomatic arch. Deep part: inner surface of the zygomatic arch |
|---|---|
| Insertion | Superficial part: lower half of the lateral ramus and angle of the mandible. Deep part: upper half of the ramus and coronoid process |
| Nerve Supply | Masseteric nerve (branch of the mandibular nerve V3) |
| Blood Supply | Masseteric artery (from the maxillary artery) |
| Actions | Mandibular elevation (jaw closing) — the most powerful jaw closer per unit cross-section; Assists jaw protrusion (superficial part) |
|---|
Botulinum toxin injection into the masseter reduces bruxism-related pain, masseter hypertrophy, and temporomandibular joint loading. The masseteric nerve (V3 motor branch) is harvested and transferred to the facial nerve zygomatic branch for smile restoration — the patient learns to smile by biting. Results are excellent with 85% achieving grade 3+ smile symmetry.
The masseter is the prominent cheek muscle palpable between the zygomatic arch and the mandibular angle, becoming firm during jaw clenching and visible in hypertrophy.
Bruxism-driven masseter enlargement producing square jaw and TMJ pain managed with botulinum toxin injection and occlusal splint.
