Cephalometric Measurements in Adolescents with Class I Normal Occlusion

Objectives: Cephalometric norms (CN) used by orthodontists come from ideal occlusions or occlusions undefined by Angle Class.  The objectives of this study were to (1) describe CN for a random sample of adolescents with Class I normal occlusion (CIN), (2) develop adolescent CN, and (3) test the hypothesis that CN of genders are similar.     

Methods: Radiographs of adolescents (19 male, 19 female, mean age=12.0 years) were taken from the Iowa Facial Growth Study [IRB permission].  Fourteen cephalometric measurements (11 angular, 3 linear) were recorded with a cephalometric protractor and digital calipers.  Intra-rater reliability correlations (r = .9774-.9981, p < 0.0001) showed excellent agreement between duplicate measurements.  Gender differences were analyzed using Student’s t-test.  Visual comparisons of genders were generated using histograms of measurement variables.   

Results: None of the adolescent cephalometric variables measured in this study showed significant differences between genders (p > 0.05).   Non-statistical comparisons of means in this study (G) with previous means: Downs (D), Riedel(R), Michigan (M), Taylor & Hitchcock (TH), Harris (H), Saksena (S) yielded mostly similarity.  Dissimilarities included FH/N-Pog 4.8ᵒ (1sd) higher in (D); MP/FH 7.2ᵒ (1sd) lower in (D); Inter-incisal angle 7.4ᵒ (1sd) higher in (D); upper incisor/A-Pog 3 mm (1sd) lower in (D); and male N-Me distance 6mm (1sd) higher in (M).        

Conclusions: The null hypothesis predicting no differences between adolescent males and females was accepted for all cephalometric variables.  The differences between the present study means and those of previous studies may be explained by (1) sample differences, selection of subjects, and perhaps growth maturation in (D).  Most previous CN observed appear satisfactory for adolescents. 

Support: University of Iowa College of Dentistry Dows Research Award.