Initial displacements and variations of eight human child skulls owing to high-pull headgear traction determined with laser holography.

In this study eight macerated, human child skulls (dental age approximately 9.5 years) were subjected to a standardized high-pull headgear traction system. Tensile forces from 0.5 to 3.5 N (1 N = 0.1 kgf) per side were produced to the maxillae. Displacements of skeletal components were determined at 22 indicator points per skull by means of laser holography. Coordinated displacements and variations in amount and direction were established in all skulls. The overall amount of displacements was primarily a characteristic of an individual skull, not of a particular displacement. On the average, the maxillae were displaced in a slightly downward and posterior direction almost parallel to the occlusal plane. No deformations of skeletal components were seen. Results indicated that initial displacements of the maxillae and other skeletal components are not in the same direction as the direction of applied forces.