Constancy of the angle between the Frankfort horizontal plane and the sella-nasion line: A nine-year longitudinal study

Abstract

Objective: To investigate the constancy of the angle between the Frankfort horizontal plane (FH) and the sella-nasion line (SN) using longitudinal data. Materials and Methods: Longitudinal lateral cephalometric data of 223 children (116 girls and 107 boys) from 6 to 14 years of age were used. The angle between FH and SN (SNFH), the distance from FH to the nasion (NFH), the distance from FH to the sella (SFH), and the differences between the NFH and SFH (Δ) were also measured. All data were analyzed statistically using independent ttests and mixed-effect regression model analysis. Results: The mean SNFH values showed some minor fluctuations, ranging from 9.26° to 9.74° in girls and 8.45° to 8.95° in boys. The mean NFH and SFH values gradually increased according to age irrespective of sex. There were statistically significant differences by sex for all measurements at several ages. The annual change in SFH and D showed sexual dimorphism. Conclusions: There are variations among individuals in the angle between the FH and SN. However, within an individual, the angle does not vary significantly over time during the observation period. © 2014 by The EH Angle Education and Research Foundation, Inc.