Characteristics of protrusive and lateral excursions of the mandible in children with the primary dentition.

This study characterizes the mandibular protrusive and lateral excursions of children with primary dentition. With use of a Selspot system, the protrusive and lateral excursions of nine children with the primary dentition and nine adults with the permanent dentition were measured and compared. This system was able to analyse the simultaneous movements of multiple points on the mandible of a subject in three dimensions. Furthermore, the system proved appropriate for use in young children because of the small burden imposed on them during the measurements. Using this subject-friendly system, the directions of the mandibular excursion for five reference points on the mandibular dental arch at each measurement distance (i.e. at 0.5 mm intervals) for three projected angles (frontal, sagittal and horizontal) were calculated. From the results it was found that the excursions of the primary dentition can move more horizontally and more forward with small descent compared with the permanent dentition. The underlying reason for these findings may be physiological growth, maturation, and adaptation of the occlusal function.