Oral treatment device

An oral treatment device includes a head for use in treating an oral cavity of a user, the oral cavity including a plurality of oral cavity zones, and an inertial measurement unit, IMU, operable to output signals dependent on position and/or movement of the head. The oral treatment device includes a controller configured to receive signals from the IMU indicating position and/or movement of the head relative to the oral cavity, and process the received signals using a trained non-linear classification algorithm to obtain classification data. The classification algorithm is trained to identify, from the plurality of oral cavity zones, an oral cavity zone in which the head of the oral treatment device is located. The controller is configured to control the oral treatment device to perform an action using the obtained classification data.