Establishing Age, Race/ethnicity, and Gender-Specific Dentofacial Reference Values for Children and Adolescents; a 3D Orthodontic Diagnostic Analysis

Abstract

Background: Orthodontic diagnosis and treatment planning relies heavily on 2D imaging. Currently 2D lateral cephalograms, which expose the entire skull to ionizing radiation to reveal cranial reference structures, are the most commonly used tool. A novel diagnostic protocol suggested the Natural Head Position, NHP, and the Maximum Convexity of the Cornea (MCC) as clinically visible replacements of the radiographically visible cranial reference planes. Based on that, adult average norms have been established and validated; however, we fall short of providing dentofacial norms that are age, race/ethnicity, and gender specific for the population of interest (4-18yr). Aims: a) Establish the reliability of orthodontic measurements generated via 3D diagnosis and analysis. b) Establish age, race/ethnicity, and gender specific dentofacial reference values in the form of means, standard deviations, and 3D mesh composites via 3D diagnostic analysis. Materials & Methods: a) 3D records of 25 subjects were analyzed by 2 calibrated orthodontic residents to generate dentofacial orthodontic measurements and report intra- and inter-operator reliability values of images superimposition, landmarking, and use of multiple facial images. b) 3D dental and facial images of 240 healthy subjects with symmetrical faces and near ideal occlusion were obtained and analyzed by a single experienced operator to generate age, race/ethnicity, and gender specific reference values while using NHP and MCC as references. Results: a) Average ICC (intra-class correlation) values for the measurements generated during the three different registration steps (registration of facial and dental images, landmarks digitization, use of different facial images) were (0.941, 0.906), (0.916, 0.905), and (0.87, 0.90) respectively. b) 960 reference values, their standard deviations, and twelve 3D meshes were generated to describe dentofacial structures of children and adolescents. Significant shape differences were noted in all 3 planes of the dentofacial complex. Maxillary and Mandibular sagittal and vertical position, as well as angulation of upper and lower incisors were distinct between groups (p-value <0.01) and showed an increasing trend with age. There is a significant difference in the overall shape between adolescent males and females (p-value <0.01). Conclusion: 80% of orthodontic measurements created via 3D landmark based registration and analysis are reliable; however, some facial landmarks would benefit from physical palpation and marking to improve its reliability. Dentofacial significant shape differences exist in all 3 planes due to age, race/ethnicity, and gender in individuals below 18 years. This radiation free diagnostic method can be supplemented with a limited field low dose CBCT of the maxilla and mandible to eliminate the need of irradiating the entire cranial complex in children and adolescents.