The effects of orthopedic forces on the craniofacial complex utilizing cervical and headgear appliances.

1. A three-dimensional anatomic model of a human skull was produced with birefringent materials for photoelastic analysis. By means of photoelastic techniques during application of high-pull and cervical extraoral traction, stresses were visualized within the model. 2. Extraoral anchorage affected the position of the maxillary molar and its resulting alveolar development. Cervical headgear had a much greater tipping effect on the maxillary molar than did the high-pull headgear. Both appliances examined could produce stresses which may be transmitted to distant eraniofacial sutures. As opposed to high-pull traction, cervical pull in general stressed more areas and to a much greater degree. 4. The pterygoid plates of the sphenoid bone, the zygomatic arches, the junction of the maxilla with the lacrimal bone and the ethmoid, and the maxillary teeth were affected by both types of headgear. 5. Only cervical traction produced stresses at the frontal process of the maxilla and the Zygomaticofrontal suture. 6. There were two findings which had not been previously reported: First, cervical traction tended to open the palate in the posterior region. Second, high-pull traction produced compressive stresses at the junction of the right and left maxillae inferior to the anterior nasal spine.