Reliability of a measuring-procedure to locate a muscle-determined centric relation position

Although reproducibility of centric relation position, determined with an anterior deprogramming device, a leaf gauge, is widely accepted among clinicians, data confirming statistical evidence are lacking in the current literature. The objective of this study was to prove clinical reliability of a measuring-procedure to locate the centric relation position, determined with the leaf gauge. A sample of 15 subjects (6 men, 9 women, age 22 to 46), assessed with the Research Diagnostic Criteria to rule out any TMD-signs, was selected. Three observers each took three sequential interocclusal records with the leaf gauge, to mount a set of casts into the centric relation position in an articulator. Out of 15 subjects, 12 (5 men, 7 women) fitted criteria of precision--three out of three interocclusal records for each of the three observers--in a split-cast procedure. The applied statistical method is an analysis of variance model (ANOVA) with two factors for 3 observers and 12 subjects. The variance components estimation procedure is MIVQUE (0). The a was set at 0.05. No significant difference between observers for the measured variables sagittally (XL, XR), transversally (YL, YR), and vertically (ZL, ZR) could be found. MIVQUE variance components estimates for observers is < 0, varies for subjects from 0.04 to 0.20 and varies for error from 0.12 to 0.25 mm. Reliability of a measuring-procedure to locate a muscle-determined centric relation position could be established satisfactory.