Effective treatment plan for maxillary protraction: is the bone age useful to determine the treatment plan?

A major skeletal effect of reverse-pull headgear is a forward movement of maxilla, via remodeling of the circummaxillary sutures. We hypothesized that an evaluation of bone age would help to determine the effective planning and optimum timing using reverse-pull headgear. Differences in the cephalometric measurements between the initiation of treatment and after 1 year of treatment were calculated from 60 Japanese patients in mixed dentition with skeletal Class III malocclusions. Bone age was appraised by the Tanner-Whitehouse 2 method using hand-wrist radiographs at the initiation of treatment. The control groups (mean chronologic age, male 10.3 years and female 9.6 years) were treated by lingual arch and/or chincup, and the reverse-pull headgear groups (mean chronologic age, male 9.7 years and female 9.4 years) by reverse-pull headgear. The forward movement of the maxilla and increase in the palatal length were larger in the bone age-based younger male reverse-pull headgear subgroup than in the bone age-based older male reverse-pull headgear subgroup. The increase of SNA in the male reverse-pull headgear group was significantly larger than that of the female reverse-pull headgear group, which had a more mature skeletal status than the former. In the male reverse-pull headgear group, the forward movement of the maxilla and increase in the palatal length showed significant inverse correlation with the bone age, but not with the chronologic age. These results support our hypothesis that the bone age is a useful clinical indicator to determine the effective treatment plan with reverse-pull headgear.