The purpose of this study was to determine the accuracy of the prediction methods which are frequently used in the clinic, such as Moyers’, Tanaka and Johnston’s, Song’s Hixon and oldfather’s, Kaplan’s, Smith’s. These prediction methods were compared to the data, which were obtained from 100 Kyung-Hee University students (50 males and 50 males and 50 females) with normal occlusion of permanent dentition, using a retrospective statistical analysis. The standard periapical radiopgraphs for the lower premolars using 16-inch long cone technique and the yellow stone dental casts were taken from each samples. The mesiodistal widths of 4 incisors, canine, premolars were measured on the dental casts, and those of premolars were measured on the radiographs. The correlation coefficients, paired samples t-tests, regression coefficients between the actual measuredments of the samples and the predicted measurements of each methods were analyzed.
The results obtained were as follows:
1. The prediction methods using periapical radiographs tended to show a stronger correlation than the methods using dental casts; the correlation coefficients between the actual widths of the lower canine and premolars and the predicted
widths of the tested methods were higher in Smith, Kaplan, Hixon & Oldfater, and Tanaka & Johnston (p<0.001).
2. The moyers’ probability chart at 65% showed a tendency toward the least difference between the actual measurements and the predicted widths of the lower canine and the preolars, and the methods of Smith, Kaplan, Tanaka & Johnston also showed a less difference.
3. By means of evaluation in correlation coefficients and paired smaples t-tests, the Smith and Tanaka & Johnston in male, and the Moyers’ 65% and Song in female showed a high tendency toward accurate methods.
4. The regression equations by models that are derived from the study were as follows :
Male(Lt.) :Y=10.799+0.475X Femle(Lt.) :Y=7.427+0.609X (Rt.) :Y=11.043+0.462X (Rt.) :Y=8.475+0.556X
5. The regression equations by radiographs that are dericed from the study were as follows : Male(Lt.) :Y=6.5651+0.9720X Femle(Lt.) :Y=4.8656+1.0632X (Rt.) :Y=7.8610+0.9060X (Rt.) :Y=4.5483+1.0843X
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