Condylar retruded contact position and intercuspal position correlation in dentulous patients. Part I: Three-dimensional analysis of condylar registrations.

A three-dimensional condylar analysis of the ICP relative to the RCP was completed for 75 patients by using a system of styli adapted to an arcon articulator. The recorded sagittal condylar positions were seen in three of the four quadrants, the posterior-superior quadrant was devoid of registrations. The percent of registration was approximately equal for the right and left sides; anterior-inferior quadrant, 60%; posterior-inferior quadrant, 30%; and anterior-superior quadrant, 10%. Midcondylar value of the ICP presented the smallest standard deviation but the data concerning condylar position were unreliable because symmetrical and asymmetrical movement may produce similar midcondylar values. Seventy-two percent of the anterior-posterior and 45% of the superior-inferior condylar ICP recordings of patients fell within the range of a dentally healthy sample of young men. Only 2% of recordings the patients were outside this range in a superior direction. These data were nearly equal numerically for the right and left sides and conformed to the anatomic freedom of TMJ. Slightly more than 57% of the sample had an MLD greater than 0.3 mm compared with a dentally healthy sample. There was a 42% greater incidence of skew greater than 0.7 mm and a 22% greater occurrence of tilt greater than 0.7 mm in the dental patient sample, compared with the findings of Hoffman et al. An index ICP asymmetry was proposed that indicates the relative value of skew and tilt in a single quantitative factor. Three mandibular movements were identified, skew and tilt with angular components and MLD, translation. These three movements have 3 degrees of freedom, right or left movement or no movement, resulting in 27 permutations. The combination of these elements make it difficult to determine condylar position from occlusal midline observation.