The Road to Three-Dimensional Imaging in Orthodontics

This paper examines the origins of 3-dimensional craniofacial measurement. It briefly tracks the development of measurement methods from the plaster casts and facial moulages of the early 20th century to the cone beam computed tomographic scanners of today. The fundamental difference in design between cone beam scanners and conventional computed tomography scanners is described in their difference in primary function; cone beam scanners are optimized for the location of hard tissue structures, such as teeth and bone, whereas computed tomography scanners were originally optimized for the detection of subtle distinctions in the radiopacity of different bodily soft tissues under different conditions of health and disease. The advantages and limitations of several attempts at quantitative measurement of the skull and face in 3 dimensions are noted.