Objective To investigate congenital abnormal number of deciduous teeth among 3-year-old children in Haimen District, Nantong, Jiangsu Province, so as to provide basic data for preschool children’s oral health care.

Methods A total of 5 768 newly admitted to kindergarten children aged 3 − 4 years old who received health check at Nantong Haimen District Maternal and Child Health and Family Planning Service Center were recruited as study subjects from Aug, 2020 to Dec, 2021. Professional examinations were conducted by dental practitioners, and the number, types, positions, and deformities of missing primary teeth were recorded for situation analysis.

Results  Among 5 768 children, 125 had congenital abnormal number of deciduous teeth, with an incidence rate of 2.17%. There were 122 cases of congenital tooth loss, with an incidence rate of 2.12% (122/5 768). Among those, one person was oligodontia with 14 missing teeth, and 121 person were hypodontia with 1 − 2 missing teeth; 12 cases were missing upper dentition, accounting for 9.84%, and 110 cases were missing lower dentition, accounting for 90.16%. Among 122 children with missing teeth, there were 182 congenital primary teeth missing, including 80 missing left teeth (43.96%) and 102 missing right teeth (56.04%); Among 182 primary teeth missing, 135 were primary incisors missing, accounting for 74.18%. There were 3 supernumerary teeth, with an incidence rate of 0.052%, among which, 2 were patients with cleft lip and palate.

Conclusion  The main missing primary teeth in Haimen, Nantong region is hypodontia with 1 − 2 missing teeth. Mandibular primary incisors were dominating, and the missing primary teeth in the lower jaw are significantly more than those in the upper jaw. Supernumerary teeth are mainly caused by cleft lip and palate.