[Space maintenance for the premature loss of the second primary molar].

Space reduction after the premature loss of the second primary molars is one of the important factors affecting the occurrence of malocclusion, often increasing the demand for orthodontic treatment. It has great significance to select and apply appropriate appliances to maintainthe space soon after the premature loss of the second primary molars. The space should be maintained until the adjacent teeth and the successors erupt successfully. This review summarizes the selection and clinical application of the space maintainer for the premature loss of the second primary molars in different periods, to improve dentists' awareness of the importance of space maintainers and to provide advises for clinical choices.