The aim of this study was to use a microsensor to investigate the association among overjet reduction, treatment duration, and wear time of the van Beek activator. The study sample comprised patients (n=28) with a mean age of 11.60 (±1.25) years at start of treatment treated with the van Beek activator. The prescribed wear time was 12hours per day. The evaluation period was limited to the first 3 appointments. The wear times during the 3 intervals were assessed. Treatment periods with good compliance were characterized by a wear time of 8hours or more per day. The medians of overjet were 9.00mm at the start of treatment and 5.75mm at the third appointment. The mean total wear time throughout the evaluation period was 7.75 (±3.66) hours per day. Significant correlations were found at the 3 intervals. Patients with a mean wear time of 8hours or more per day achieved significantly greater overjet reductions. Patients with good compliance of at least 5months showed significantly greater overjet reductions. Significant overjet reduction was achieved with a minimum daily wear time of 8hours for at least 5months. The level of compliance had a strong tendency to be maintained throughout the treatment period. No patient achieved the prescribed wear time of 12hour per day.