Minimum detectable change in occlusal load - normative data for healthy and head and neck cancer populations

Traditionally, pain has been a signal to de-intensify jaw exercises for trismus to prevent tissue damage. It is unknown whether patients who have undergone surgery or radiotherapy for head and neck cancer have sufficient sensation to detect changes in occlusal load. This study sought to compare the minimum detectable occlusal load in a cohort of patients with head and neck cancer (HNC) and compare this with healthy controls. Twenty patients who were treated for HNC and 20 healthy controls were recruited from a single institution. A purpose-built pressure transducer was used to measure the minimum detectable force (measured in Newtons) applied to the jaw and the interincisal distance. Analysis was conducted using a mixed effects linear regression. The mean minimum detectable occlusal load in patients with HNC was 18.7N compared to 4.5N in healthy controls (mean difference 14.3N, 95% CI 12.2N to 16.4N, p < 0.001). Adjusted IID predicted force (0.15N per-mm IID, 95% CI 0.09 to 0.2, p < 0.001) with a weak interaction between treatment with radiotherapy and IID in HNC patients (p = 0.85). Patients who have been treated for HNC are less sensitive to changes in force applied to the jaw. This is concerning given that most jaw stretching devices use an unregulated and unknown amount of force to achieve greater mouth opening.