Trismus is traditionally considered being a late effect of cancer therapy with functional deficits becoming clear in the first year after completing radiation therapy. These deficits can rapidly progress to a state of functional impairment. The most common treatment for trismus is physical therapy comprising an active range of motion (ROM) exercises, hold and relax techniques. Once trismus has developed, it may be hard to reverse. Thus, prevention with a program of self-care is important for managing this side effect. This study want to test the effect with adjunctive devices plus exercise to prevent trismus.

Inclusion Criteria:

1. Age is greater than or equal to 20 years old.
2. Those who are able to communicate in Mandarin and Taiwanese and have no reading or listening or writing disabilities can fill out the questionnaire by themselves or with the assistance of the researcher.
3. Diagnosed with head and neck cancer, and is expected to receive head and neck radiation therapy for the first time.
4. A clear consciousness, no severe cognitive impairment or mental symptoms.
5. Willing to participate in this research and obtain consent.

Exclusion Criteria:

1. People with known temporomandibular joint disorders.
2. The maximum opening degree is less than or equal to 25 mm.
3. Those who have received radiotherapy for the head and neck in the past.
4. Those who have been diagnosed by a physician for poor wound healing after surgery and unable to perform mouth-opening rehabilitation exercises.