The application of Moire magnification to high-resolution studies of human premolar eruption

The optical phenomenon of Moire magnification can be used to provide real-time measurements of the position of an erupting human premolar, with a resolution of 0.1 μm or better. A new instrument for this purpose, which allows repeated measurements in the same individual, is described. Cyclic changes in the position of the erupting tooth in concert with the heartbeat, with a magnitude of 0.05–0.35 μm, can be discerned. An unusual cyclic rhythm, with a period of 20–50 s, was observed.