Effects of Mouth-opening Training on the Maximum Interincisal Opening

PURPOSE:The purpose of the study was to investigate the effect of mouth-opening training with follow-up telephone calls for reducing postoperative trismus in patients with oral cancer.

METHODS:The study is a randomized clinical trial using repeated measures. Sixty-eight patients admitted at a general hospital in Taiwan for oral cancer surgery were recruited and randomly assigned to either the intervention or control group. All subjects were instructed to practice mouth-opening exercises three times a day every day for three months. Subjects in the intervention group received additional 6 follow-up phone calls to enhance mouth-opening exercise adherence. Data on maximum interincisal opening and mandibular function impairment were collected before surgery, at one-month, and three-months after discharge, using the TheraBite Range-of-Motion scale and Mandibular Function Impairment Questionnaire.

The purpose of the study was to investigate the effect of mouth-opening exercise training with follow-up telephone calls for preventing postoperative trismus in patients with oral cancer. The specific aims were to test the intervention effects on enhancing mouth-opening exercise practice, MIO, and mandibular function. We hypothesized that the intervention group would show 1) better adherence to mouth-opening exercises, 2) greater MIO, and 3) better mandibular function over time, compared to the control group.

The study is a randomized clinical trial using repeated measures. A convenience sample of 68 oral cancer patients was recruited and randomly assigned to either the intervention or control group according to a list generated by the Random Allocation Software. Subjects in both groups received two 30-minute individual trainings on the mouth-opening exercises before discharge from the hospital. Subjects were instructed to practice the mouth-opening exercises three times a day, every day, for 12 weeks. Subjects in the intervention group received additional 6 follow-up phone calls (at 1, 2, 3, 4, 8 and 12-week after discharge) from the interventionist to enhance mouth-opening exercise adherence. Data on MIO and mandibular function impairment were collected before surgery, at one-month, and three-months after discharge, using the TheraBite Range-of-Motion scale and the Mandibular Function Impairment Questionnaire. The study was approved by the research ethics committee of the hospital where the data were collected.

All statistical analyses were carried out using the SPSS statistical package version 20.0 (SPSS Inc., Chicago, IL, USA). Characteristics of the subjects were summarized by percentages, means, and standard deviations (SDs). Chi-squared tests or Fisher's exact tests and two independent samples t-tests were used to examine group baseline equivalency. Value changes of study outcomes (MIO and mandibular function impairment) and mouth-opening exercises performed from T1, T2, to T3 were expressed in two study groups. A general linear model was used to model these outcomes as a function of main group effect and main time effect. An interaction term (group difference by time) was added into each model to investigate the synergistic effect of the intervention with time. Both the stability analysis and the analysis of repeated relationships were performed by generalized estimation equations (GEE).

Eligibility Criteria:
Inclusion Criteria:

1. aged 18 years or older
2. diagnosed with oral cancer
3. scheduled for a primary curative oral cancer surgery
4. able to communicate in Mandarin or Taiwanese
5. obtained medical clearance from the patient's attending physician to participate in the study

Exclusion Criteria:

1. diagnosed with lip or tongue cancers which were less relevant to trismus
2. had central incisors extracted during the surgery