Longitudinal study of relative growth rates of the maxilla and the mandible according to quantitative cervical vertebral maturation

Abstract

Introduction: The purpose of this study was to investigate the relative growth rates (RGR) of the maxilla and the mandible according to quantitative cervical vertebral maturation (QCVM) of adolescents with normal occlusion.

Methods: Mixed longitudinal data were used. The sample included 87 adolescents (32 boys, 55 girls) from 8 to 18 years of age with normal occlusion, selected from 901 candidates. Sequential lateral cephalograms and hand-wrist films were taken once a year for 6 consecutive years. The growth magnitude (GM) and RGR of the maxilla and the mandible were measured and analyzed.

Results: GM and RGR were not always consistent, because subjects had different periods of time between the QCVM stages. GM was not as reliable as RGR. RGR had no significant sex differences in the maxilla and the mandible, in spite of different decelerating curves. However, statistically significant sex differences were found in the GM of mandibular measurements. The greatest growth potentials were not synchronized between the maxilla and the mandible. For both sexes, the greatest RGR of maxillary length and height was in QCVM stage I; then, deceleration occurred. The greatest RGR of mandibular length and height was in QCVM stage II, and the next largest was in QCVM stage I.

Conclusions: Understanding the RGR can provide references for orthodontic treatment and orthognathic surgery.