Abstract
The purpose of this study was to characterize mandibular movement during protrusion in anterior crossbite children with primary dentition. Mandibular movements were measured using a TRI-MET®, an optoelectronic analysis system with six degrees-of-freedom, at a sampling frequency of 100 Hz. This measurement data was transferred to a graphics workstation for analysis. The subjects with primary dentition were categorized into two groups according to their interocclusal relations, group one had normal occlusion and group two had anterior crossbite. The former group consisted of 20 children (mean age: 5 years and 6 months), and the latter group consisted of 15 children (mean age: 4 years and 9 months) . Anterior-posterior range, right-left range, superior-inferior range and three-dimensional linear distance of the incisal point and the condylar points during protrusion were estimated by using multilevel statistical models. Correlation coefficients between incisor and condylar distances were evaluated at both the inter-individual and intra-individual levels. The study's results were:
1) Protrusion of the anterior crossbite group was characterized by smaller ranges and distances of both the incisors and condyles than children with normal occlusion. This suggests that when the teeth are at maximum intercuspal position the condyle is located more anteriorly in anterior crossbite children than in normal children.
2) High correlation coefficients in both groups of children, suggest that condylar movements during protrusion can be reliably estimated from incisor movements.
3) Intra-individual correlations of normal occlusion children were larger than their inter-individual correlations, but the reverse was true for anterior crossbite children.
