This trial evaluates how well a new therapeutic device works in managing trismus in patients who received radiation treatment for head and neck cancer. Radiation therapy is a common form of treatment in patients with head and neck cancers. However, changes to surrounding tissue following radiation therapy may lead to trismus, an inability to open the mouth fully. This can create significant functional impairment leading to malnutrition due to impaired chewing, risk of dental infections due to impaired oral hygiene, difficulty with speech, and decreased health-related quality of life. Exercise therapy is the mainstay of treatment for post-radiation trismus to help improve mobility and flexibility and increase range of mouth opening. This new device is non-invasive and is similar to other jaw stretching devices where a mouthpiece is placed between the teeth and a hand-lever is used to spread open the upper and lower jaw. However, it will also have additional sensors to measure pressure exerted by the hands and jaw as well as the distance to open the mouth which could help guide therapy. This study may help doctors customize a device to patient-specific needs, provide real-time feedback, and encourage compliance for trismus exercise therapy.

PRIMARY OBJECTIVE:

I. To assess the clinical efficacy of the trismus device, as measured by the change in maximum interincisal opening over the six-week treatment period.

SECONDARY OBJECTIVE:

I. To assess participants compliance rates and jaw opening pressures when using this device.

OUTLINE: Participants are assigned to 1 of 2 parts.

PART I: Participants test the trismus device and complete questionnaires on study.

PART II: Participants undergo exercise therapy with the trismus device under supervision of a speech language pathologist on study.

Participants will be on study for up to 6 weeks with a follow-up visit 7 days after completion.

Inclusion Criteria:

• Male or female >= 18 years of age at visit 1.
• Documentation of a radiation-induced trismus diagnosis as evidenced by one or more clinical features consistent with the trismus phenotype (maximum interincisal opening (MIO) < 35 mm) and a history of head and neck radiation
• Written informed consent (and assent when applicable) obtained from subject or subject's legal representative and ability for subject to comply with the requirements of the study.

Exclusion Criteria:

• Presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the patient or the quality of the data.
• Minors (age < 18 years) or patients with inability to provide informed consent.