Comparison of maxillary and mandibular growth

In this longitudinal study, serial lateral cephalometric radiographs were used to compare growth patterns of the maxilla and mandible, with hand-wrist radiographs used to assess skeletal maturity. The sample comprised 28 untreated subjects (15 female, 13 male) who were followed from ages 6 to 20 years. All subjects had Class I malocclusions without anterior crossbites. Absolute values and incremental changes for linear and angular cephalometric measurements were recorded and analyzed, and the relative growth-rate formula was used to provide an accurate index of acceleration and deceleration of growth. The SNA angle did not change significantly with age, but the SNB angle increased significantly in the male subjects. The ANB angle decreased continuously until age 14. The palatal plane descended significantly from the horizontal plane. The anterior and posterior nasal spines moved at about the same rate. The mandible grew in length twice as much as the maxilla from ages 6 to 20. With growth, the facial profiles of the male subjects became straighter as the chin became more prominent. The female subjects had less incremental growth and duration of growth of the mandible, so that the profiles remained more convex. Overall, skeletal and chronologic ages did not differ significantly, except at ages 10 and 16 in the female subjects. Individual variability pointed to the need for assessing each patient's pattern in the general guidelines of the group pattern.