Vertical changes in Class III patients after maxillary protraction with expansion in the primary and mixed dentitions.

PURPOSE This study determined the vertical response of class III patients in the primary, mixed, and late mixed dentition phases fitted with a protraction mask and expansion. METHODS The before and after cephalometric records of 112 patients divided by sex were analyzed at ages 3 to 6, > 6 to 9 and > 9 to 12 years to assess the vertical changes. Data was correlated by means of paired t tests and scheffe's multiple contrasts. The study showed: (1) descriptive statistics and the before and after results in males and females in the different age groups; (2) the changes in males and females disregarding age; and (3) the changes at the different ages disregarding gender. RESULTS The main vertical changes in this study were seen in the FMA angle, GoGn to SN, Facial axis, and ANS-Me between the ages of 3 to 6 years. Between 6 to 9 years, a lesser significant opening existed and no significant change could be seen in the GoGn-SN angular measurement. Between 9 to 12 years all linear and angular measurements became non significant with the exception of ANS-Me. CONCLUSIONS Class III corrections should be started as early as possible, once the diagnosis is made and cooperation allows it. Most of the changes were seen between the ages of 3 to 6 years. No significance was seen after the age of 9 years with the exception of ANS-Me in both males and females (P < 0.05). No differences were seen between males and females in all measurements at the different ages with the exception of occlusal plane to SN (P < 0.05) between 3 to 6 years. The vertical changes were mostly seen in the mandible with no direct benefit from the changes in the midfacial region.