Ultrasound is well suited for imaging of teeth and their internal structures due to its high resolution, its ability to detect small variations in acoustic impedance, its ability to penetrate hard tissues and restorations, and its non-ionizing nature. Of particular clinical interest are those structures that are difficult to detect with radiography, including microcracks, subsurface caries and fractures, occlusal caries, and defects that are adjacent to restorations. This book outlines the challenges and advantages associated with dental ultrasound, details existing dental imaging and dental ultrasound techniques, and presents a novel approach to the detection of subsurface dental structures. This book is a revised and reformatted version of the Ph.D. dissertation, submitted to the Biomedical Engineering Interdepartmental Program at the University of California, Los Angeles in 2005, originally entitled "Development of an ultrasound imaging system for the detection of subsurface fractures and caries in human teeth."