Norms for Occlusal Cant in Angle Class I Normal Subjects

Objectives: The purposes of this study were to assess in Class I normal occlusion (CIN) subjects (1) cant of the occlusal plane between the most buccal images of the right & left upper and lower second molars in posterior-anterior (PA) cephalograms compared to a cranial reference horizontal, determined by the intersection of the floor of the anterior cranial fossa at the lateral walls of the orbits, (2) difference between the occlusal and reference planes, and (3) gender differences. These data will aid in PA cephalometric assessment of patients.
Methods: Twenty males and 18 females with CIN occlusions were selected from the University of Iowa Facial Growth Study. Selection criteria: (1) appropriate PA cephalogram, (2) permanent first and second molars in occlusion, and (3) no orthodontic treatment prior to date of PA cephalogram. Two measurers, each at two separate measuring times, measured the occlusal cant and the cranial reference horizontal using Dolphin™ software. An average of two measurements was used for data analysis. Statistical analyses included one and two-sample t-tests. Inter- and intra-observer reliabilities were analyzed with intra-class correlation.
Results: Intra-class correlation coefficients for inter-and intra-observer agreement were 0.92 and 0.89, respectively. The mean (SD) difference between the occlusal cant and the cranial horizontal was 0.18 (1.31) degrees. Mean differences between the occlusal cant and cranial horizontal did not differ significantly from zero (p=0.4071), and no significant difference existed between males and females (p=0.6868).
Conclusions: The angle between the occlusal cant and the cranial reference horizontal did not differ significantly from zero in patients with Class I normal occlusion in the permanent dentition. The mean (SD) was 0.3 (1.5) degrees in females, and 0.1 (1.2) degrees in males. These norms will be useful in the diagnosis of asymmetric deviations of the occlusal plane in the permanent dentitions of orthodontic patients.