A longitudinal study of condylar growth and mandibular rotation in untreated subjects with class II malocclusion.

Abstract

Condylar growth intensity, mandibular growth rotation, and the association between growth intensity and rotation were evaluated in 32 untreated subjects with Class II malocclusions. Condylar growth was measured on serial lateral head films annually from ages 8 to 13. The analysis showed that the growth intensity of the condyles varied only slightly between girls and boys, with boys growing more. Fluctuations in growth intensity were observed in all subjects from year to year. None of the individuals maintained a consistent growth velocity over two or more consecutive years. The average condylar growth intensity was two to three mm per year throughout the period from age 8 1/2 to 12 1/2 for both sexes, with boys growing slightly faster than girls at some ages. The greatest growth velocity observed was eight mm in one year, which was seen in one boy. Three girls had as much as six mm of condylar growth in one year. Average mandibular rotation was -0.8 (+/- 0.5 SD) per year in boys and -0.6 degrees (+/- 0.6 SD) in girls, with great individual variation for both sexes. Ninety percent of the subjects showed some degree of anterior or forward rotation; only one subject demonstrated posterior rotation and three demonstrated almost no rotation. No clear relationship was found between amount of condylar growth and mandibular rotation. This study shows that condylar growth intensity varies considerably between subjects and from year to year in each subject, and suggests that clinicians need to be conservative when estimating treatment length for a patient with a Class II malocclusion.