A dental CT apparatus includes a control system arranged to move a radiation source and an imaging sensor on the opposite sides of an imaging station. The control system includes at least a first imaging mode designed for imaging patients and means for selecting at least one second imaging mode in which the source of radiation and the imaging sensor are driven during an exposure at an angular velocity of less than 4 degrees/second. A digital three dimensional models of teeth are generated based on imaging impressions or models of teeth by a CT apparatus provided with at least one specific imaging mode for the purpose.