The inapplicability of formulae to determine vertical dimension.
The accuracy and precision of certain external cephalometric measurements were investigated on a subject presenting optimal conditions, using ten operators. Due to difficulties in identifying landmarks and tissue compressibility, the standard deviation of a measurement for ten replications ranged from 0 . 3 to 1 . 7 mm, while the "between operators" standard deviation was no better than 2 . 0 mm. Measurement accuracy was also poor: that of primary interest, subnasale-gnathion, had a bias of the order of 7 mm, judged by a radiographic determination. A minimum denture success rate of 97% is equated with a standard deviation of 1 mm in the design freeway space. A recently published regression equation for predicting occlusal vertical dimension has a minimum error of prediction of 5 . 8 mm and thus is considered an inadequate predictive tool. The errors demonstrated in facial measurements suggest that using formulae to predict occlusal vertical dimension is unlikely to produce clinically acceptable results.
D002508:Cephalometry; D005145:Face / Q000033:anatomy & histology; D006801:Humans; D008297:Male; D008433:Mathematics; D011336:Probability; D012107:Research Design; D014716:Vertical Dimension