|Limitation of Mouth Opening (Trismus)
|Photos showing a patient with Trismus and the Use
of Spatulas to Ameliorate the Trismus
|Last Updated 20th March 2020
|Photo showing a patient with Trismus using a Trismus Screw. These have to be
used with caution as they can severely traumatised the 'front' teeth and may lead to
Trismus is a painful condition that restricts normal mandibular movement and function as a result of masticatory
musculature spasms. Patients are unable to open their mouth within the normal range (35 to 55 mm [average is 40
mm]; 3-finger wide).
Trismus is diagnosed from clinical examination of the Maximal Inter-Incisal Distance (MID) of less than 40 - 45 mm caused by contracture of
the masticatory musculature and not by obstructive joint impingement.
This represents the distance from the incisal edge of the maxillary (upper jaw) and mandibular (lower jaw) incisors. In œdentulous
(toothless) patients, it is measured between the maxillary and mandibular alveolar ridges of less than 40 - 45 mm will be classified as
|Trismus (Ætiological Causes & Differential Diagnosis of Limited Mouth Opening
|Evidence suggests that gender may be a factor in vertical mandibular opening. In general, males display greater mouth opening
In general, all conditions resulting in an impaired ability to open the mouth within a normal range is classified as trismus.
Trismus has a number of potential causes, which range from the simple and non-progressive to those that are potentially life-threatening.
Trismus can have consequences including impaired mastication (chewing), difficulty in speaking, in achieving adequate oral hygiene and in
access for oral care. If left untreated, degenerative processes in the masticatory muscles, with disuse atrophy, may ensue.
- Limited mouth-opening ability
- Deviation of the jaw toward the affected side (muscles not functioning properly because of spasms)
- Diffuse facial swelling and fever (only if associated with infections)
- Pain severity: severe pain in acute condition (if there are trigger points in muscles); dull, aching pain if muscle spasms persist for a long
- Pain at rest
- Difficulty to open the mouth wide and attain full-range motion
- Inability to chew or bite on solid foods
- Discomfort when yawning
- Difficulty to brush teeth and follow routine oral hygiene care, which can lead to bad breath and a high risk of caries
- Pain in one or more masticatory (chewing) muscles
- Sensation of muscle tightness, cramping, or stiffness
- Difficulty with respect to speech; inability to receive proper dental care
Rule Out Other Pathologies
- Thoroughly review the patient's dental and medical history
- Ask about the onset, nature, progression, aggravation, radiation of pain and relieving factors
- Ask about any dental treatment, joint clicking and locking, trauma, infections, medical conditions, radio-therapy or drug intake
- Inquire about pain in neck, shoulder and back muscles
- Inquire about sleep bruxism (clenching / grinding / tooth tapping) or daytime para-function (clenching / gum chewing / fingernail biting)
- Perform a complete extra-oral and intra-oral examination
- Check for visible muscle fasciculation (pathognomonic for myo-spasm / trismus diagnosis)
- Check for facial asymmetry
- Measure maximum mouth opening (check for inter-incisal distance) and lateral range of jaw motion
- Palpate the masticatory muscles and check for tenderness (some areas may be extremely tender due to deep pain input from myo-
fascial trigger points)
- Palpate the neck muscles (especially sterno-cleidomastoid muscle) and upper shoulder muscles (trapezius)
- Examine the tempero-mandibular joint (TMJ) (check for any tenderness, uncoordinated movement, clicking sounds and crepitus)
- Look for partially erupting 3rd molars and gingival inflammation
- Check teeth for any wear facets and / or occlusal disharmony
- Perform a radiographic investigation.
- Panoramic radiographs may be advisable to look for any associated abnormalities with TMJ’s.
- CT and MRI scans may be required to rule out pathologies in structures such as TMJs, ears, etc.
Based on the clinical history and signs, a diagnosis of trismus is determined.
- Facial trauma with / without bone fracture
- Non-odontogenic infections (tonsillitis, meningitis, tetanus, parotid abscess): trismus is a hallmark of masticatory-space infections and
may also occur along with pericoronitis
- Needle stick injury to the medial pterygoid muscle
- Fibrosis (when masticatory muscles are involved in field of radiation)
- Prolonged mouth opening (following any dental procedure like dental extraction / high points after dental restoration)
Treatment (including patient education, self-care management, rest and analgesics) should be directed towards the underlying causes.
- Partially impacted tooth: extraction of offending tooth may be required
- Infection: antibiotic therapy
- Trauma: referral to an Oral Surgeon / Oral & Maxillofacial Surgeon
Common Initial Treatments
- Advise the patient to follow a soft diet and avoid solid foods
- Suggest heat therapy (placing moist hot towels on the affected area for 15-20 minutes every 1 hr)
- Suggest taking analgesics: Paracetamol, .5 - 1g every 4 - 6 hours or Ibuprofen 200 - 400 mg every 4 - 6 hours
- Muscle relaxants may be used in combination with analgesics or alone. Benzodiazepines may also be used, such as diazepam (2 - 5
mg, 3 times / day)
- Physiotherapy treatments may be required to establish normal function (exercises will include neck stretching, chin tuck, massaging of
masticatory muscles and other jaw stretching)
- Mandibular opening devices might be considered in some cases, but most likely provided by a physiotherapist or dental specialist
- Avoid any daytime jaw parafunction (gum chewing, finger nail biting, tooth clenching, etc.)
- Work with a physiotherapist to strengthen their jaw muscles, if needed (in acute conditions)
|Photos showing various trismus treatments. a: spatulae b: trismus screw c: therabite d: dynamic splint