Objectives: To measure skull thickness in a group of subjects with skeletal Class II and a group with skeletal Class III malocclusion and compare these results with a group with Class I occlusion.
Setting and sample population: Department of Orthodontics, School of Dentistry, University of Copenhagen. The Class II group comprised 25 females aged 17-42 (mean 26.0). The Class III group comprised 53 patients, 29 females aged 17-39 (mean 24.2) and 24 males aged 17-38 (mean 22.6). The control group comprised 39 subjects, 19 females and 20 males, aged 22-30, with a neutral occlusion and normal vertical and sagittal jaw relationship.
Material and methods: The thickness of the frontal, parietal and occipital bones was measured on lateral radiographs of patients with skeletal Class II and Class III and compared with the control group. Method error ranged from 0.30 to 0.60 mm and reliability coefficients from 0.79 to 0.97. Unpaired t-tests were used for evaluating differences in thickness.
Results: Females with skeletal Class II malocclusion had a significantly thinner occipital bone and thicker frontal bones than the control females. Skull thickness in Class III malocclusion was comparable to the control group.
Conclusion: The most important outcome of this study was reduced skull thickness in the occipital area and thickening of the frontal bone in females with skeletal Class II malocclusion compared with females with Class I. Deviations in the theca cranii are thus associated with skeletal Class II malocclusions.