The Trouble with Trismus

Twenty-two percent of members filling in a poll about trismus in our Facebook group have limited mouth opening after surgery or (chemo)radiation. I am one of them and will write this post partly through the lens of my own experience.

I think I fit into the category of moderate to severe trismus as I am only able to open my mouth about 1 1/2 fingers wide. A lot of our members have had success using tongue depressors (the most common method), stretching using their fingers or by use of a Therabite. Below is the three finger full mouth opening we would all like to have.

A few of us have chronic trismus. Below is an extraxt from a Chris O’Brien Lifehouse study on trismus:

Head and neck cancer treatment often leads to significant physical and functional impairments. One of the most distressing impairments is trismus, a condition characterized by limited mouth opening. Trismus can severely compromise patients’ quality of life, affecting essential functions such as eating, speaking, and maintaining oral hygiene. Trismus exercises are an important method to improve functional outcomes and promote the overall well-being of patients with head and neck cancer-induced trismus.

How is trismus measured?

Trismus can be graded as follows:

Severe: 15 mm or less interincisally (between the teeth)

Moderate: 16–25 mm

Mild: 25–35 mm

Normal: Greater than 35 mm 

Trismus is caused by scarring of the muscles that open and shut the jaw because of surgery or radiotherapy and is a real downer.

Because of trismus, my dentist and prosthodontist struggle to operate within my mouth and I can no longer be intubated through the mouth during a general anaesthetic. In my daily life I barely notice it because I eat soft food anyway and have enough opening to clean my teeth. Some patients have worse problems as you can see in this video from the Mouth Cancer Foundation.


If it’s treated early trismus can be fixed or prevented from getting worse. Speech language therapists and physios can help with this (mainly SLTs) and for most patients an increasing number of tongue depressors placed in their mouth over days and weeks can do the trick. Some departments make a gadget by joining the sticks together and others will provide a Therabite.

It’s well documented that passive stretching works better than active stretching. That means that you let the device open the mouth for you. You can do a passive stretch with the fingers of both hands.

The Chris O’Brien Lifehouse in Sydney has invented a 3D printed device that might not be so hard on the teeth and which has been successfully trialled with patients who suffer from chronic trismus.

Here are the last two paragraphs from their Phase II clinical trial.

Our study has several limitations. Most notably our study lacks a control group, however all participants had chronic trismus that was not improving without intervention. While Restorabite™ has the unique capability to individually select the force applied to the mouth, at this stage the optimal force, duration, and frequency of exercises is unknown. Future studies will apply computational techniques to identify patient specific upper and lower force limits during trismus therapy.

In conclusion, this phase II cohort trial demonstrates the safety and clinical utility of Restorabite™, a new trismus device which uses measurable regulated and incremental force to treat trismus induced by head and neck cancer and its treatment, resulting in improved opening of the oral cavity and quality of life. The results of this study were either equitable, or superior to other studies conducted internationally.

In conclusion, trismus is something you want to get onto fast, the speech language therapist can help you with it and if all else fails there are new products coming onto the market in due course!

For more detailed info see this link but always check with your medical team first before you start your exercises.