The aims of the study were to adapt a computerized system to epidemiologic conditions, for rapid full-mouth measurements of alveolar bone levels from X5-magnified periapical radiographs and to analyze the variations in measurement due to different system components. Full-mouth measurements of interproximal alveolar bone height in percentage of root and tooth lengths were completed within an average time of 15 min per set of radiographs. An analysis of variance showed that the examiner variation in measurement of a linear scale distance was 0.02 mm. The measurement accuracy was different for different distances; each distance (d) measured with this system should therefore be calibrated with the equation Y = -0.007-0.014 (log3d-1.50), where Y is the estimate of measurement accuracy. The present computerized system enabled rapid recordings and demonstrated good measurement precision and accuracy; these are valuable features in epidemiologic investigations.
The aim of the study was to develop a sensitive measuring method enabling direct evaluation of gingival swelling to be made as registered on dental casts. On two separate occasions, when different degrees of severity of gingival inflammation were present in the same subject, reversible hydrocolloid impressions were taken of the mandible. The casts obtained were located successively in identical three-dimensional relationships in a field of interference fringes generated by two intersecting beams of collimated helium-neon laser light, and were photographed. The evaluation of the moiré pattern obtained directly by superimposition of the two images of the surface studied indicated that a decrease in gingival height of 0.38 mm in the direction of the camera had occurred between the two occasions. The use of a computer-based image-processing system considerably improved the visibility of the pattern. The reproducibility of the impression technique, as well as the relocation and superimposing techniques, proved satisfactory at the moiré resolution used (0.19 mm). The method has potential application in clinical experimental research, and therefore warrants further evaluation.
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