Trismus

Introduction:

Trismus is a common presentation by the patient in routine dental practice. This condition causes difficulty in opening mouth which in turn impairs eating, interferes with oral hygiene, restricts access for dental procedures, and may adversely affect speech and facial appearance.

Trismus has number of potential causes and it’s important to recognize the underlying cause for effective management of this condition

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Definition:

Trismus in greek is Tonic contraction of the muscles of mastication.

The Normal Mouth Opening Range:
Range- 40-60 mm (avg-35mm)
Males display greater mouth opening

The Normal Lateral movement is 8-12 mm

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Causes Of Trismus (Etiology)

Several conditions may cause or predispose an individual to develop Trismus.

1. Intra-Articular Causes:

A- Ankylosis
B- Arthiritis Synovitis
C- Meniscus Pathology

Ankylosis:
- True Bony Ankylosis: can result from trauma to chin, infections and from prolonged immobilization following condylar fracture
Treatment- several surgical procedures are used to treat bony ankylosis, Eg: Gap arthroplasty using interpositional materials between the cut segments.

- Fibrous Ankylosis: usually results due to trauma and infection
Treatment- trismus appliances in conjunction with physical therapy.

Trismus Appliances:

Indications:
A- Intracapsular (TMJ) pathosis
B- Bony interferences from styloid or coronoid process
C- The presence of foreign body
D- Muscle fibrosis or immature scar tissue

Types Of Trismus Appliances:

A- Externally activated appliances
- Dynamic bite opener
- Threaded, tapered screw
- Screw type mouth gag
- Fingers
- Tongue blades
- Continuous-dynamic jaw extension apparatus.

B- Internally activated appliances

- Tongue blades
- Plastic tapered cylinder

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2. Extra-Articular Causes:

A- Infection
B- Dental treatment
C- Trauma

D- TMJ Disorders
E- Tumors and Oral care
F- Drug Therapy:
G- Radiotherapy and Chemotherapy
H- Congenital / Developmental Causes:
I- Miscellaneous disorders

A- Infection
Odontogenic- Pulpal
- Periodontal
- Pericoronal

Non-Odontogenic- Peritonsillar abscess
- Tetanus
- Meningitis
- Brain abscess
- Parotid abscess

The hallmark of a masticatory space infection is trismus. Or infection in anterior compartment of lateral pharyngeal space results in trismus. If these infections are unchecked, can spread to various facial spaces of the head & neck and lead to serious complications such as cervical cellulitis/ mediastinitis.
Treatment- Elimination of etiologic agent along with antibiotic coverage

Trismus or lock jaw due to masseter muscle spasm, can be a primary presenting symptom in tetanus, Caused by clostridium tetani, where tetanospasmin (toxin) is responsible for muscle spasms.
Prevention- primary immunization (DPT)

B- Trismus Related To Dental Procedure:
Oral surgical procedures- extraction of lower molar teeth may cause trismus as a result either of inflammation involving muscles of mastication or direct trauma to the TMJ
Inaccurate positioning of the needle when giving inferior alveolar nerve block before extraction
Barbing of needles at the time of injection followed by tissue damage on withdrawal of the barbed needle causes post-injection persistent paresthesia, trismus and paresis
Treatment- in acute phase
Heat therapy
Analgesics
A soft diet
Muscle relaxants (if necessary)
When acute phase is over the patient should be advised to initiate physiotherapy for opening and closing mouth.

C- Trauma:
Fractures, particularly those of the mandible and Fractures of zygomatic arch and zygomatic arch complex,Accidental incorporation of foreign bodies due to external traumatic injury
Treatment- fracture reduction, removal of foreign bodies with antibiotic coverage

D- TMJ Disorders:
Extra capsular disorders – myofacial pain
Intra capsular problems – disc displacement, arthritis, fibrosis etc
Acute closed locked conditions – displaced meniscus

E- Tumors And Oral Malignancies:
Rarely, trismus is a symptom of nasopharyngeal or infra temporal tumors/ fibrosis of temporalis tendon, when patient has limited mouth opening, always pre malignant conditions like oral sub mucous fibrosis (OSMF) should also be considered in differential diagnosis

F. Drug Therapy:
Succinyl choline, phenothiazines and tricyclic antidepressants causes trismus as a secondary effect. Trismus can be seen as an extra-pyramidal side-effect of metaclopromide, phenothiazines and other medications.

G. Radiology / Chemotherapy:

- Complications of Radiotherapy:
1. Osteoradionecrosis may result in pain, trismus, suppuration and occasionally a foul smelling wound.
2. When muscles of mastication are within the field of radiation, it leads to fibrosis and result in decreased mouth opening.
- Complications of Chemotherapy:

Oral mucosal cells have high growth rate and are susceptible to the toxic effects of chemotherapy, which lead to stomatitis.

H. Congenital / Developmental Causes:
Hypertrophy of coronoid process causes interference of coronoid against the anteromedial margin of the zygomatic arch.
Treatment-Roronoidectomy
Trismus-pseudo-camtodactyly syndrome is a rare combination of hand, foot and mouth abnormalities and trismus.

I. Miscellaneous disorders
- Hysteric patients: Through the mechanisms of conversion, the emotional conflict are converted into a physical symptom. Eg: trismus

- Scleroderma: A condition marked by edema and induration of the skin involving facial region can cause trismus

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