REPRODUCIBILITY OF BONE HEIGHT MEASUREMENTS MADE ON SERIAL RADIOGRAPHS

THE OBJECTIVE OF THIS STUDY was to determine the reproducibility of al veolar bone height measurements made on digitized images of serial rad iographs using 3 different alignment systems for taking serial radiogr aphs: 1) XCP Rinn System, 2) XCP Rinn System modified to include an al ignment pin, and 3) I / EGAD system (impression based-electronically g uided alignment device). Eighty duplicate films taken 1 hour apart of randomly selected anterior or posterior sites for alignment systems 1 and 2 were taken on 40 subjects, Thirty-eight duplicate films were tak en of posterior and anterior sites on 19 subjects with alignment syste m 3. Cemento-enamel junction alveolar crest measurements were made on digital images using the side-by-side technique. Image pairs of serial radiographs were dichotomized into well-matched and poorly matched gr oups based on subjective evaluation of the geometric likeness. Of thos e taken with system 1, 47% were well matched; with system 2, 62%; and with system 3, 98%. The measurement error of change in radiographic bo ne height, defined as twice the standard deviation of difference (mm), was determined. This varied between 1.03 mm for poorly matched radiog raphic pairs taken with alignment system 1 and 0.52 mm for all radiogr aphic pairs taken with alignment system 3, These results can be used t ogether with power calculations to select an alignment system for a pa rticular study. For example, power calculations indicate that detectin g a bone change of 0.5 mm using the I / EGAD system would require one- third of the subjects needed when using the XCP Rinn method.