Oral treatment device

An oral treatment device includes an inertial measurement unit, IMU, operable to output signals dependent on movement of the oral treatment device. The oral treatment device includes a controller configured to receive signals from the IMU indicating movement of the oral treatment device relative to the oral cavity, and process the received signals using a trained classification algorithm to obtain classification data, the classification algorithm being configured to determine whether the oral treatment device is being moved according to a predetermined movement type. The controller is configured to control the oral treatment device to perform an action using the classification data.