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How can radiation limit jaw opening?

5 April 2023

There are around 12,400 new cases of head and neck cancer in the UK every year. Head and neck cancer can be found in the mouth and lips, voice box, throat, salivary glands, nose and sinuses, and at the back of the nose and mouth. Of these, mouth cancer is the most common type, and one which dental professionals may be able to spot in its early stages during routine dental check-ups – with symptoms including mouth ulcers and lumps in the mouth. [i]

The effect of radiation on the jaw joint

Cancer and trismus are linked in a number of ways. Cancer can cause trismus through: tumours in the jaw muscles or joint, surgery to remove the tumour, or radiation to treat the cancer. Of these, radiation therapy to treat head and neck cancer is the most common cause. [ii] Not all patients who receive treatment will experience trismus, but it is thought to affect between 10 and 40% of patients. And, it doesn’t impact everyone in the same way, with some patients still able to open their mouth normally, and others unable to do so. [iii]

Radiation therapy can cause scar tissue to form in the jaw muscles, making them feel stiff and painful. When this happens, it can be hard for patients to move their jaws normally and open their mouths. The amount of treatment a patient receives can increase the risk of getting trismus. [iv] For instance, a patient who is being treated for a recurrence, or who is receiving a higher dosage, is likely to be at higher risk for trismus than those having treatment for the first time. [v]

Treating trismus caused by scar tissue

Trismus can make it difficult to open the mouth, making tasks like oral hygiene, eating, and talking a challenge. Because of this, it is important to recommend treatment and exercises to help patients improve their range of motion.

There are a number of ways to manage trismus. These include:

  • Massaging the jaw muscles
  • Exercising the jaw muscles
  • Maintaining good posture [vi]

The sooner the signs of trismus are noticed, and management techniques begin, the more likely patients are to regain their usual jaw function. However, if patients have recently undergone surgery, make sure it is safe before recommending exercises.

Massaging the jaw muscles is helpful to relieve tension. Suggest that patients massage the jaw muscles 2 or 3 times a day, and that they try not to clench their jaw when they are stressed. This will help to keep the jaw muscles relaxed.

There are a number of exercises trismus patients should try, which aim to increase their range of motion. These exercises intend to stretch the jaw muscles, and patients should feel a stretching sensation, but no pain. Exercises include:

  • Opening the mouth as wide as they can (without pain) and holding it
  • Moving jaw from left to right and holding it
  • Passive stretching exercise [vii]

Passive motion has been shown to be very effective, with research showing it can reduce pain and inflammation as well as increasing range of motion. The exercise is designed to stretch the jaw joint and muscles, without additional strain for the patient.[viii]

The OraStretch Press Rehab System is designed to prevent and treat trismus using passive motion to stretch the jaw, joint and facial tissues to increase mobility, flexibility and function. By using the OraStretch Press, patients can increase their range of motion, improve jaw function and reduce pain. And, with proper use, patients can expect to gain 1-2 mm per week in range of motion.[ix]

Supporting patients in recovery

It is important to look out for signs of trismus in patients who are having radiation treatment. Limited mouth opening can have a serious impact on patients’ quality of life, including causing problems with speech, and nutrition, because some patients struggle to fit food into their mouth. And, because patients might struggle to clean their teeth properly, they may experience more oral health problems without treatment. Generally, the sooner treatment is started the better, to help limit the effects and maximise mouth opening.










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