A stereo dental x-ray with viewing device. The Ritter Intra-Oral Stereoscope was patented in 1933 by the Ritter Dental Manufacturing Co. of Rochester, NY (Pieper and Kester 1931). Established in 1887, Ritter is still a leading provider of dental equipment.

X-rays were discovered by Wilhelm Röntgen in 1895. Within two weeks of Röntgen's publication, the German dentist Wilhelm Walkhoff took the first x-ray images of human teeth. However, x-rays weren't commonly used for dentistry until the 1950s (radiation exposure and electrocution were legitimate concerns.)

Although they were a huge step forward for medicine, x-rays had limitations. Interpreting 3D geometry in an x-ray could be difficult because important visual cues—occlusion and shading—were missing:

Their examination therefore does not allow one to appreciate the shape of the surfaces and to know the order of superposition of the various planes of the object. This last point constitutes a serious defect, especially for application to diagnosis (Marie and Ribaut 1897, 613).

Fortunately, a solution was close at hand. Stereography had been popular since the 1850s and "within months" of Röntgen's discovery was proposed as a way of clarifying x-ray geometry (Gallay 2019, 105).