Assessing the effectiveness of Hospital-Based Manufactured Medical Device Restorabite for treatment of Trismus in adults after head and neck cancer surgery (Cohort 2)

The primary objective is to determine optimal exercise duration and force to treat Trismus. Description of Interventions: • Passive jaw range of motion exercises using Restorabite as per randomised Arm • Active jaw range of motion exercises using Restorabite as per randomised Arm • 10 x 1hr weekly sessions face to face or over telehealth with speech pathology. Gradual progression through the force hierarchy as clinically indicated. • Home practice: daily for 20 minutes for duration of study (10 weeks) Passive and active jaw range of motion exercises is a continuous exercise performed with Restorabite. It involves inserting the pressed down Restorabite between the front teeth and letting the device stretch the jaw (passive motion exercise) then bite down on the mouth guards (active motion exercise). Then repeat the letting go of the bite (passive motion exercise) and biting down on the device (active motion exercise). Participants will be given a Restorabite device and randomised to one of seven daily exercise programs (20 minutes daily). Arm 1. Low force for maximum of 30 seconds of 4 repetitions x 5 times with Restorabite Arm 2. Low force for maximum of 60 seconds of 2 repetitions x 5 times with Restorabite Arm 3. Low force for maximum of 120 seconds of 1 repetition x 5 times with Restorabite Arm 4. High force for maximum of 30 seconds of 4 repetitions x 5 times with Restorabite Arm 5. High force for maximum of 60 seconds of 2 repetitions x 5 times with Restorabite Arm 6. High force for maximum of 120 seconds of 1 repetition x 5 times with Restorabite Control. Stacked tongue depressor for maximum of 30 seconds of 5 repetitions x 5 times Low force is defined as maximum intensity of up to 30N (insert position 4 on Restorabite device) High force is defined as maximum intensity of up to 50N (insert position 8 on Restorabite device) Participants will be given a device, and the treatment will last for 10 weeks. Participants will be asked to attend 10 sessions of 1-hour weekly appointments with the speech pathologist. These appointments can be conducted either in person or via Telehealth. Follow up appointments will be required at 6 months and 12 months after the study treatment finishes. At the first and last appointments and 6 months and 12 months follow up appointments, participants will be asked to answer Quality of Life (QoL) questionnaires. Optional semi-structured interviews, using an interview guide, will be conducted with patients to evaluate their experiences using a device for trismus at the end of the intervention. These 30-60minute interviews will be conducted via video conferencing (Zoom) once during the course of the trial. To monitor adherence to the intervention speech pathologists will closely follow up participants. To increase the adherence to the intervention, speech pathologists will set up a 10-week appointment plan at the beginning of the trial and also offer tele-health appointments.