The quality check of plugs in human teeth and the detection of marginal defects and abrasion effects during a specified time period has been improved by photogrammetric methods, using imagery from the scanning electron microscope (SEM) for a three dimensional measurement. Due to the small magnification of the micrographs, caused by the object size, the geometry of the scanning operation required the use of perspective formulas during the photogrammetric set up and data registration procedure. Unneglectable image distortions, effected by the small image scale, has been detected by the use of a calibration grid and the stereo models where extended by an additional third image to meliorate the quality of the photogrammetric measurement. The quality of data acquisition was proved by mapping the whole tooth surface. The relationship between the models of different epochs of one object was established by the detection of features on the tooth surface without artifical control points and the breakdown of a specified part of the plug during the time of observation is documented.
M. Gruber, M. Gruber,
"Untersuchungen von zahnfiillungen anhand von REM-Zeitreihen", Proc. SPIE 1395, Close-Range Photogrammetry Meets Machine Vision, 13952Q (1 August 1990); doi: 10.1117/12.2294341; https://doi.org/10.1117/12.2294341