Has hypodontia increased in Caucasians during the 20th century? A meta-analysis

It has been claimed that agenesis of permanent teeth has increased over the years. The present study tested this hypothesis in Caucasians. Published data on the prevalence of children with one or more congenitally missing permanent teeth were selected on the basis of strictly imposed criteria. Using a meta-analysis, the data were evaluated and presented chronologically. Furthermore, the selected publications were checked for differences in the prevalence of agenesis between the male and female populations. Finally, information on the occurrence of upper and lower premolars as well as upper incisor agenesis was collected and calculated as a percentage of the total number of congenitally missing teeth. From 42 studies on this subject, 19 were selected based upon six stringently applied criteria. Chronological classification of the percentage of children with congenital absence of one or more permanent teeth revealed relatively higher percentages since 1957. Fourteen out of the selected studies presented data on sex distribution. In all but one publication girls tended to have a slightly higher occurrence of missing teeth compared with boys of the same age. The second lower premolars were most often agenetic, whereas missing upper laterals occurred almost equally as agenesis of the upper second premolars. The considered period of time is too short and the available data too limited to describe a possible trend in the human dentition. However, this meta-analysis seems to confirm that hypodontia has been diagnosed more often in recent studies.