Three dimensional x-ray imaging systems are described in this application. In particular, this application describes a 3D dental intra-oral imaging (3DIO) system that collects a series of 2D image projections. The x-ray imaging system comprises a housing, an x-ray source attached to a articulating or motion gantry configured to move the source within the housing to multiple positions, an x-ray detector array located on an opposite side of an object to be imaged from the x-ray source, where the detector array is synchronized with the x-ray source to capture 2D images of the object when the x-ray source is located in multiple imaging positions, and a processor configured to accept the 2D images and reconstruct a 3D image. The multiple imaging positions can be located on a plane substantially parallel to the x-ray detector array. Other embodiments are described.