Longitudinal changes in Class I subjects with moderate mandibular skeletal protrusion.

Two groups of Class I females were followed from 6 to 18 years of age. At the initial evaluation, subjects in one group had normal sagittal jaw-base relationships, while those in the other group had moderate mesial relationships between the jaw bases. The purpose of this study was to compare craniofacial morphology and growth in these two groups. Subjects with mesial jaw-base relationships had mandibular skeletal protrusion due to a more forward positioning of the mandible relative to anterior cranial base. Other morphological group differences involved jaw-base relationships (but not jaw size). All the observed group differences were present at age 6; no new differences were observed later. Some differences stayed significant up to age 18, while others became less distinct with time. Incremental growth in the groups was comparable. Similar growth of the jaws apparently helped to maintain initial group differences in jaw-base relationships.