Proportions of Malocclusions in Japanese Female Adolescents over the Last 40 Years

Purpose: To assess the prevalence of malocclusion in schoolgirls at a private high school and whether it has increased or not over 40 years by comparison with previous surveys on early and middle adolescence in Japan. Materials and Methods: Conventional dental examination including evaluation of occlusion was performed in 2,378 schoolgirls who were enrolled in the seventh and the tenth grade between the years 2004 and 2006. The presence of maxillary protrusion, anterior crossbite, edge-to-edge incisor relationship, open bite, deep bite and crowding of teeth was recorded by visual inspection. The prevalences of various types of malocclusion were compared between the two grade groups and with data from the previous surveys. Results: The proportions of malocclusions in the tenth grade (55.7%) and seventh grade (55.3%) were found to be similar. The prevalences of maxillary protrusion, anterior crossbite, edge-to-edge incisor relationship, open bite, deep bite and tooth crowding in the seventh grade students were 9.4%, 0.6%, 4.1%, 0.6%, 8.4% and 19.1%, respectively. The corresponding values in tenth grade students were almost the same except for deep bite, which was significantly lower than that in the seventh grade. Comparison with previous surveys indicated that the proportions of malocclusions taken as a whole had not changed over 40 years, whereas anterior crossbite, edge-to-edge incisor relationship, open bite and tooth crowding had decreased significantly within the last 20 years. Conclusion: Significant changes in the proportions of malocclusions as a whole in adolescents were not found over the last four decades. Keywords: high school, Japanese, malocclusions, orthodontics, prevalence, student