['The aim of this study was to evaluate the effect of TheraBite exercises on mouth opening and to analyze factors influencing this effect in a patient record evaluation.', 'Effect of exercises with a TheraBite to treat trismus was evaluated in 69 head and neck cancer patients of two university medical centers. Mouth opening was measured as interincisal distance in millimeters. Patient, tumor, and treatment characteristics were analyzed for their relationship with change in mouth opening. Variables univariately associated (p\u2009≤\u20090.05) with change in mouth opening were entered in a logistic regression analysis as possible predictors for an increase in mouth opening of the smallest detectable difference of 5 mm or more.', 'Mean initial mouth opening was 22.0 mm (SD 6.4); mean increase in mouth opening was 5.4 mm (SD 5.7). "Chemotherapy", "medical center", and "time from oncological treatment to start exercises" were significantly associated with an increase in mouth opening. In the logistic regression analysis, "medical center" (β\u2009=\u20091.97) and "time from oncological treatment to start exercises" reduced the odds of reaching an increase in mouth opening of 5 mm or more, β\u2009=\u2009-0.11 per month.'] Does theraBite exercise to treat trismus secondary to head and neck cancer?