Video data acquired during a three-dimensional scan of dentition provides a source of still images that can be displayed alongside a rendered three-dimensional model of the dentition, and the two views may be synchronized to provide a common perspective of the model’s subject matter. The blades of the impeller are identical, but are arranged in pairs such that impellers of different hydraulic characteristics are formed with blades of the same shape. , referred to as a SmartStack module, that can be coupled directly to a device with a SmartStack module controller. A non-volatile memory device coupled with the microprocessor is operative to store fault indications when present. The user’s set of activities may be shared with one or more other users.