CEPHALOMETRIC A-POINT CHANGES DURING AND AFTER MAXILLARY PROTRACTION AND EXPANSION

The purpose of this study was to analyze the treatment and posttreatme nt maxillary changes achieved with maxillary protraction therapy. The cephalometric records of 25 consecutively treated Chinese children wit h Class III malocclusions (mean age 8.4 years) were analyzed for cepha lometric A point changes, which were then compared with an untreated, age and sex matched Class III control sample. A cephalometric maxillar y superimposition technique was used to differentiate between the skel etal and the local contributions to the total A point change. Results showed that 6 months of maxillary protraction therapy produced a mean A point advancement of 2.4 mm compared with 0.2 mm in the control grou p. Of this advancement, 75% was found to be due to skeletal maxillary advancement and 25% was attributed to local remodeling. Significantly less downward movement of A point was found with treatment compared wi th the controls, which could be related to the direction of force appl ication, No significant differences were found in the horizontal and t he vertical movements of A point between the treatment and the control groups during the 12-month posttreatment period, indicating stability of early maxillary protraction in patients with Class III malocclusio ns.