Incisor and mandibular condylar movements of young adult females during maximum protrusion and lateratrusion of the jaw

This study evaluated the correlations between condylar translation and inci sor movements during maximum protrusion and lateratrusion. The sample was 2 7 adult females (23-35 years old), selected for normal temporomandibular fu nction, occlusion, and skeletal patterns. Condylar and mandibular central i ncisor movements [linear distances (LD) and curvilinear pathways (CP)] were recorded in three dimensions for 20 s with an optoelectric (Optotrak(R)) j aw-tracking system while each participant performed multiple maximum protru sive and lateratrusive cycles. Masticatory analysis and multilevel statisti cal programs computed the three-dimensional movements of the incisors and c ondylar hinge axis during protrusion and lateratrusion, CP of the incisor p oint averaged 12.0 mm (9.3 mm LD) during protrusion, 13.0 mm (11.5 mm LD) d uring right excursion and 12.3 mm (11.0 mm LD) during left excursion. CP Of the condyles averaged 11.9-12.9 (9.2-9.5 LD) mm during protrusion. During lateratrusion the contralateral condyles moved anteroinferiorly 11.6-14.1 m m (9.5-10.2 mm LD); the ipsilateral condyles moved posterolaterally 5.8-6.8 mm (2.3-2.5 mm LD). The left condyles demonstrated more movement than the right condyles during protrusion and than the contralateral condyles during laterotrusion. Relative variation, as measured by the coefficient of varia tion, was greater for the movements of the ipsilateral than contralateral c ondyles. Incisor movements were only moderately related to condylar movemen ts between individuals and between replicates; LDs showed stronger correlat ions than CPs; and correlations were stronger for lateratrusion than protru sion. While incisor and condylar movements were not affected by repeated pr otrusion, incisor CP (approx. 0.2 mm/cycle) and LD (approx. 0.1 mm/cycle) i ncreased significantly with repeated excursive movements to the left and ri ght. It was concluded that (1) incisor protrusion and lateratrusion provide moderately reliable measures of condylar translation: (2) the linear dista nces that the incisors move during lateratrusion provide the best measure o f contralateral condylar translation: and (3) condylar movements are not af fected by repeated protrusion or lateratrusion. (C) 2000 Elsevier Science L td. All rights reserved.