The purpose of this study was to look for associations between lower incisor movement and working and balancing condylar movement during lateral excursion in children with primary dentition and adults with permanent dentition. Mandibular movement was recorded using a TRI-MET (an optoelectronic analysis system with six degrees-of-freedom) at a sampling frequency of 100 Hz. The movement data was transferred to a graphics workstation for analysis. Subjects were categorized by age into two groups. The primary dentition group consisted of 19 children (mean age: 5 years and 5 months, s.d.: 8·7 months), and the permanent dentition group consisted of 22 women (mean age: 20 years and 5 months, s.d.: 26·3 months). The occlusion and TMJ in both groups were normal, with no history of orthodontic treatment. Three orthogonal excursive ranges and the 3D linear distance of the incisal and balancing and working condylar points, along with inter- and intra-individual correlations between the incisor and the balancing and working condyles during lateral excursion, were estimated by using multilevel statistical models. Lateral excursion in children with primary dentition was characterized by smaller incisor excursive ranges and 3D linear distance than in adults, and stronger inter- and intra-individual correlations between incisor and balancing condylar movements than in adults. In both children and adults the lateral excursion of the incisor was a good indicator of the extent of balancing condylar movement, but not working condylar movement.
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