Effect of Oral Exercise on Trismus after Oral Cancer Radiotherapy: A Quasi-Experimental Study

Trismus is a severe complication of oral cancer treatment. Oral exercise is a potentially helpful approach for preventing or improving trismus. The study aimed to test the efficacy of an oral exercise for enhancing the maximum inter-incisal opening (MIO) in patients undergoing surgery and radiotherapy for oral cancer. This is a quasi-experimental study. A sample of 69 oral cancer patients completed the study, with 35 in the control group and 34 in the intervention group. Intervention subjects were asked to perform three 20-min oral exercise sessions per day for six months. Data on oral exercise practicing time, MIO, and mandibular function impairment were collected at the last radiotherapy exposure (T1), three months (T2), and six months (T3) after the radiotherapy. At T3, the intervention group exercised 217.1 min (95%CI: 107.4~326.7) more than the control group. The generalized estimation equations showed a statistically significant group-by-time interaction in MIO. The change in MIO score from T1 to T3, as indicated by the regression slope, was 2.5 mm (95%CI: 0.4~4.6) greater in the intervention group than in the control group. The results support the efficacy of the study intervention for improving patient exercise adherence and MIO.