Changes in atlas position with Class II activator treatment in Class II malocclusion patients

Cho, Moon Ki; Lee, Jin Woo; Cha, Kyung Suk; Chung, Dong Hwa

Abstract

OBJECTIVE
Previous studies have reported that morphological features of the first cervical vertebra (atlas) have been associated with mandibular growth direction. The purpose of this study was to show the possible positional and morphological changes of the Atlas from activator treatment in Class II malocclusion patients.
METHODS
Lateral cephalometric radiograph tracings were made at initial, middle and final stages of treatment. Angular and linear measurements of skeletal and morphological features were measured on the anatomical landmarks and reference planes.
RESULTS
The skeletal effects of activator treatment on Class II malocclusion patients were evident on ramal height, body length, effective body length, ANB, and overjet. Clockwise rotation of the long axis of the Atlas was found in Group 1, but there was no inclination change of the Atlas in groups 2 and 3. There was no significant correlation between anterior and posterior positions of the atlas or morphological change in all groups. - except for posterior movements of the Atlas found in group 1.
CONCLUSION
Clockwise rotation of the atlas axis resulted from activator treatment in Cl II malocclusion patients. Change in atlas axis can be thought of as an indicator for success of activator treatment.