Vertical dimension. Part 1: Comparison of clinical freeway space

This study was conducted in order to compare the clinical freeway space mea surements using three simple methods commonly used by dentists in their pra ctices. The study was performed in 15 young healthy subjects with natural d entition and bilateral molar support. Artificial landmarks (adhesive tape) were placed on the more prominent parts of the nose and chin of each subjec t. Vertical dimension of occlusion (VDO) was measured in the intercuspal po sition. Postural vertical dimension (PVD) was measured in the following fun ctional conditions: after swallowing saliva, after pronouncing the word "Mi ssissippi", and in a relaxed postural mandibular position (RPMP). Then, the clinical freeway space value in each functional condition was obtained by subtracting VDO from PVD value. Significant differences among clinical free way space values using three different methods were observed (ANOVA). A sig nificantly higher clinical freeway space value was found using phonetics me thod than after swallowing and with the mandible in a relaxed postural posi tion (Bonferroni multiple comparison test). No significant differences betw een swallowing and relaxed methods were found. These results seem to sugges t that the measures of clinical freeway space depend upon the method used.