Logan Steele
The jaw muscle, also known as the masseter muscle, is a thick, rectangular muscle that is essential for chewing and other oral functions. It is one of four muscles that make up the masticatory apparatus, alongside the temporalis, medial pterygoid, and lateral pterygoid muscles. The masseter muscle is divided into two parts: the superficial portion, which is tendon-like and connects to the cheekbone, and the deep portion, which is more muscular and connects to the jawbone. This muscle is responsible for elevating the jaw during chewing and plays a role in stabilizing the temporomandibular joint (TMJ). Disorders of the jaw muscle, such as myofascial pain, bruxism, and temporomandibular joint dysfunction, can cause significant discomfort and impact oral functions.
| Characteristics | Values |
|---|---|
| Number of masseter muscles | 2 (one on each side of the jaw) |
| Shape | Parallelogram |
| Parts | Superficial and deep |
| Function | Elevates the mandible, causing a powerful jaw closure |
| Controlled by | Masseteric nerve, a branch of the trigeminal nerve |
| Conditions | TMD, hypertrophy, submasseteric abscesses, myofascial pain, myospasm, myositis, bruxism, TMJ dysfunction |
| Treatments | Botox injections, surgery |
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The masseter muscle
The masseter is one of the four muscles of mastication (chewing). It is a powerful, quadrangular muscle that originates from the zygomatic arch and inserts along the angle and lateral surface of the mandibular ramus. The superficial portion of the masseter is thick and tendon-like, connecting to the zygomatic bone (cheekbone). The deep portion is smaller and more muscular, connecting to the jawbone. The entire superficial (or lateral) aspect of the muscle is covered with thin but very strong masseteric fascia. The medial, or inner, surface of the muscle is mostly related to the ramus of the mandible, almost completely covering its superficial surface.
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Masticatory muscle disorders
The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods. The muscle is shaped like a parallelogram, connecting to the mandible (lower jawbone) and the cheekbone. There are two masseter muscles, one on each side of the jaw, and each is divided into two sections: the superficial and deep portions. The superficial portion is thick and tendon-like, connecting to the zygomatic bone (cheekbone), while the smaller, more muscular deep portion connects to the jawbone.
There are several types of MMDs:
- Myofascial pain (MFP): This is characterised by the presence of one or two taut bands within the muscle, with painful trigger points that cause referred pain when compressed.
- Localized myalgia: This is a term used to describe a dull, aching pain that the patient localises to the masticatory system, usually the masseter and temporalis muscles, or cervical muscles.
- Myositis: An inflammatory condition of the muscles caused by acute trauma or infection, characterised by swelling and redness overlying the skin, increased temperature in the affected area, and resulting in jaw dysfunction and a limited range of movement.
- Myospasm: Also known as muscle cramp, this is an acute condition resulting from a sudden, involuntary, and continuous tonic contraction of the muscle. It may lead to trismus (lockjaw), pain on movement, and a severely limited range of motion of the mandible.
- Myofibrotic contracture: This involves a painless shortening of the muscle due to fibrosis in and around the remaining contractile muscle tissue following an infectious process or trauma. It results in limited mouth opening and unyielding resistance to passive jaw muscle stretch.
- Bruxism: This consists of involuntary, aimless, and repetitive teeth clenching or grinding, occurring during sleep or wakefulness due to various psychological, neurological, and orodental conditions. It can cause tooth wear, temporomandibular joint and muscle pain, and tension-type headaches.
Diagnosis of MMDs involves a careful history and clinical examination of the jaw and neck muscles, which may be followed by additional investigations. Treatment options include physical therapy, Botox injections, and, in some cases, surgery.
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Bruxism
The masseter muscle, a facial muscle connecting the mandible (lower jawbone) and cheekbone, is crucial for chewing solid foods. It is assisted by four other muscles in elevating the jaw during chewing. The masseter muscle can become hypertrophied or abnormally large due to genetic factors, repeated jaw clenching, or unknown causes. This hypertrophy is associated with a square-shaped jawline and can lead to restricted jaw movement, pain, and headaches.
Treatment for bruxism aims to address the symptoms and underlying causes. Behavioural changes, such as learning proper tongue, teeth, and lip positioning, can help ease jaw pain. Mouth guards, typically worn at night, can absorb the force of biting and protect the teeth. Botox injections are another option, blocking nerve signals to the masseter muscle. In some cases, surgery may be considered to shrink the masseter muscle, although this is less common due to its invasive nature and side effects. Regular dental exams are crucial for detecting signs of bruxism, such as flattened tooth tips, and for monitoring the condition's progression.
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Tumours
The jaw muscle, or masseter muscle, is a facial muscle that plays a major role in chewing solid foods. Tumours in the jaw muscle are rare but can occur. Jaw tumours can be benign (non-cancerous) or malignant (cancerous). Benign tumours are more common and may be caused by cysts or other abnormalities in the jawbone or soft tissue. Malignant tumours, or jaw cancer, are much less common but can be extremely dangerous as they can spread to other parts of the body.
Benign jaw tumours are typically slow-growing and may produce no symptoms at all. However, even benign tumours can grow large enough to change the structure of the jaw, cause pain, or damage teeth. The most common type of benign jaw tumour is ameloblastoma, which usually forms in the lower jaw near the back teeth (molars). It is usually benign but can become malignant in some cases. Other types of benign jaw tumours include central giant cell granuloma, dentigerous cysts, and odontogenic keratocysts.
Malignant jaw tumours, or jaw cancer, are much less common but often more serious. The most common type of jaw cancer is ameloblastic carcinoma, which forms from the tissue involved in tooth formation. It is typically found in the lower jaw near the molars. Other types of malignant jaw tumours include clear cell odontogenic carcinoma, ghost cell odontogenic carcinoma, osteosarcoma (bone cancer), and primary intraosseous carcinoma.
It is important to see a healthcare provider as soon as possible if you experience any symptoms of a jaw tumour, such as pain, swelling, or changes in tooth position. Early detection and treatment are crucial for improving outcomes and preventing the spread of cancer to other parts of the body. Treatment options for jaw tumours may include surgery, radiation therapy, or other interventions depending on the specific type and stage of the tumour.
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Jaw muscle pain
The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods. The muscle is shaped like a parallelogram, connecting to the mandible (lower jawbone) and the cheekbone. There are two masseter muscles, one on each side of the jaw. The masseter is the primary muscle that brings your teeth together when you chew.
Jaw pain is a common issue affecting millions of people. It may be mild or severe and can be caused by various factors. One of the most common causes of jaw pain is grinding teeth or bruxism, which can lead to tooth damage and pain in the temporomandibular joint and muscles. This disorder is characterised by involuntary, aimless, and repetitive teeth clenching or grinding, which can occur during sleep or wakefulness. Bruxism can be a symptom of various psychological, neurological, and orodental conditions.
Other common causes of jaw pain include gum disease, toothaches due to cavities or abscesses, and dental problems such as cracked, crowded, or sensitive teeth. Jaw pain can also be caused by injuries to the jaw or mouth, infections such as mumps, tetanus, or sinusitis, and arthritis, especially rheumatoid arthritis. In rare cases, jaw pain may be a symptom of a heart attack, as pain near the heart can be referred to the jaw.
Temporomandibular joint disorders (TMD) are a group of conditions affecting the temporomandibular joint or surrounding muscles, causing pain or tenderness. TMD can be treated by reducing jaw movements and, in some cases, Botox injections or surgery. Masseter hypertrophy, or an abnormally large masseter muscle, can also result in restricted movement of the jaw, pain, or headaches and is often treated with Botox injections.
If you are experiencing jaw pain, it is important to seek advice from a healthcare provider, especially if the pain lasts more than a week. They can help diagnose and treat the underlying cause of your jaw pain.
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Frequently asked questions
The jaw muscle is a group of muscles that work together to move the jaw. These muscles are known as the muscles of mastication or chewing.
The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The masseter muscle is a strong, thick, rectangular muscle that consists of a superficial and deep part. It is the key muscle that elevates your jaw during chewing and brings your teeth together.
Common jaw muscle disorders include myofascial pain, myospasm, myofibrotic contracture, myositis, and bruxism. These disorders can result in symptoms such as pain, stiffness, restricted jaw movement, and lockjaw.
