Trismus or Restricted mouth opening- Causes, Treatments

Trismus or Restricted mouth opening

Trismus also known as lockjaw, it is a painful restriction of mouth resulting inability to open the mouth or mandible jaw. Trismus or Restricted mouths opening is a condition, can interfere with many daily activities like chewing, swallowing, talking, maintaining proper oral hygiene, even breathing. It can be a temporary or permanent, temporary occurs much more frequently than permanent. Trismus can be accompanied

Trismus or Restricted mouth opening
Trismus or Restricted mouth opening, fig 1

Common causes of Trismus or Restricted mouth opening:

  • Impacted 3rd molar– Pericoronitis (Fig. 2), it is inflammation of soft tissue/gum around fully or partially impacted of the third molar.
  • Oral Submucous fibrosis- It is a precancerous condition.
  • Inflammation, injury of muscles of mastication- it can be because of surgical wisdom tooth extraction, it is a temporary condition.
  • Peritonsillar abscess, a complication of tonsillitis which usually presents with a sore throat, dysphagia, fever, and change in voice
  • Any severe Oral or Ear infection, abscess & cellulitis
  • Trauma, fracture of the mandibular jaw or zygomatic arch
  • Temporomandibular joint dysfunction
Pericoronitis, Fig 2

Other causes:

  • Radiation therapy to the face and neck
  • Myositis (muscle inflammation)
  • Tetanus
  • Tumors or cancer
  • Nerve damage
  • Acute osteomyelitis
  • Ankylosis of the TMJ
  • Mumps
  • Seizure
  • Congenital and developmental causes etc.


Muscles of Mastications, Fig 3

Precancerous condition – Oral Submucous fibrosis:

Oral Submucous fibrosis is a precancerous condition or premalignant condition, is a condition or lesion involving abnormal cells which are associated with an increased risk of developing into cancer. It is a morphologically altered cell which is more likely to transform into cancer than a normal cell. So if restricted mouth opening is noticed immediately visit Dentist otherwise it can easily transform cancer. The risk factor of Oral Submucous fibrosis is tobacco & betel nut.


What are the other Sign & Symptoms seen can be seen with Trismus?

  • Jaw pain
  • Headache, facial pain & ear pain
  • A “spasm” or “tight” sensation when attempting to open the mouth.
  • The difficulty with proper chewing
  • Muscle spasm etc.


Evaluation of the normal range of mouth opening:

Normal interincisal mouth-opening ranges from 35 to 45 mm. Males usually have slightly greater mouth opening than females. Mouth opening generally evaluated by using his/her three finger index (index, middle and ring fingers- Fig. 4), the normal mouth opening is three finger mouth opening. The normal lateral movement is 8-12 mm, and normal protrusive movement is approximately 10 mm. Some have distinguished mild trismus as 20–30 mm, moderate as 10–20 mm and severe as less than 10 mm.

Evaluation of the normal range of mouth opening
Evaluation of the normal range of mouth opening, Fig 4

Diagnostic approach:

  1. When you will visit a doctor & your doctor will evaluate by:
  • A doctor will review a patient’s lifestyle, medical history and discuss any previous surgery, fractures, or other trauma of your head, neck, or jaw.
  • Your Dentist may examine the oral health condition, oral mucosa, muscle & TMJ to find out how well it can open, and whether there are any abnormalities in jaw motion
  • Conduct a physical examination of your jaw and neck.


  1. X-ray & CT scan taken from the TMJ to see if there is any damage to the TMJ and surrounding structures


Treatment of Trismus or Restricted mouth opening:

  • Treatment requires treating the underlying cause of dental treatments & physical therapy. If you are facing this problem immediately visit the Dentist & follow his/her advice.
  • Additionally, control of symptoms with the proper painkiller, muscle relaxants, and warm compresses may be used.


Written by: Dr Anuran Ghosh Mondal

Mob: +91 9432580313



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