Abstract: Objective： The purpose of this study was to investigate and analyse the prevalence of malocclusion among children in primary dentition in the area of Shanghai. To provide theoretical basis for the establishment of children's oral health care measures. Methods： The investigation of occlusion in primary dentition on 2744 cases of children aged 3-6 of Shanghai was carried out by pediatric specialists.Results： The prevalence of malocclusion in primary dentition in Shanghai was 69.64% ,no significant difference was found in gender.All types of malocclusion symptoms were analysed,Deep overbite prevalence rate is highest(55.39%), followed by deep overjet(24.31%),dental crowding(21.25%),cross-bite(12.03%)and open-bite(7.22%),. 35 percent of the patients with more than two kinds of malocclusion. Conclusion： The prevalence of malocclusion in primary dentition and types of malocclusion symptoms in the area of Shanghai were obviously changed than before. A series of secorresponding preventive measures needs to formulate to prevent the occurrence and development of malocclusion in primary dentition.

Key words: Primary dentition, Malocclusion, Epidemiology, Prevalence