From the Guidelines
The muscles of mastication, including the masseter, temporalis, medial pterygoid, and lateral pterygoid, play a crucial role in jaw movement and are commonly affected in temporomandibular disorders (TMDs), which can be effectively managed with early diagnosis, reassurance, and simple physiotherapy, as well as dental interventions such as splints 1. When examining the muscles of mastication, it is essential to assess for tenderness, trigger points, and muscle hypertrophy, as these can be indicative of TMDs or other underlying conditions 1. Key points to consider in the management of muscles of mastication include:
- Accurate diagnosis through careful history and physical examination
- Identification of red flags, such as giant cell arteritis or cancer, which can present with facial pain
- Multidisciplinary team approach for chronic facial pain management
- Consideration of associated factors, such as bruxing habits, altered sensation, and impact of pain on quality of life 1. In terms of treatment, early intervention with simple physiotherapy and reassurance can be effective in managing TMDs, while more complex cases may require a multidisciplinary approach, including dental and medical interventions, such as carbamazepine for neuropathic pain 1. It is also important to note that the muscles of mastication are innervated by the mandibular branch of the trigeminal nerve (CN V3), and dysfunction of these muscles can lead to temporomandibular joint disorders, causing pain and limited jaw movement.
From the Research
Muscles of Mastication
The muscles of mastication include the lateral pterygoid, temporalis, medial pterygoid, and masseter muscles. These muscles play a crucial role in the movement and function of the temporomandibular joint (TMJ) and are often involved in temporomandibular disorders (TMD) 2, 3, 4, 5.
Temporomandibular Disorders (TMD)
TMD is a collective term for a group of musculoskeletal conditions involving pain and/or dysfunction in the masticatory muscles, TMJ, and associated structures 2. The diagnosis of TMD has significantly improved over time, with the recent Diagnostic Criteria for TMD (DC/TMD) being reliable and valid for most common diagnoses 2.
Role of Muscles in TMD
- The lateral pterygoid muscle has been shown to play a significant role in TMD, with the superior head of the lateral pterygoid muscle (SLP) seeming to have lost its diskal stabilizing function in patients with internal derangement (ID) of the TMJ 5.
- The inferior head of the lateral pterygoid muscle (ILP) has probably adapted to control the inner joint instability while continuing its own actions, and seems to have lost its functional specificity 5.
- The temporalis and masseter muscles have not been shown to be hyperactive in TMJ ID, with no significant differences in EMG activity between TMJ ID and control subjects 5.
- Botulinum toxin-A injection into the lateral pterygoid muscle has been shown to be effective in reducing symptoms of TMD, including pain and clicking of the TMJ 3.
Treatment of TMD
The treatment of TMD typically involves a combination of non-invasive therapies, including patient education, self-care, cognitive behavior therapy, pharmacotherapy, physical therapy, and occlusal devices 4. In some cases, referral to an oral and maxillofacial surgeon may be indicated for refractory cases 4.