Objective To analyze the effect of personalized customized space maintainer on tooth alignment regularity in children with dentition defect. Methods A total of 160 children with dentition defect treated at the First Afffliated Hospital of Anhui University of Chinese Medicine from February 2024 to November 2025 were selected as the research subjects. According to the random number table method, they were divided into the control group and the study group, with 80 children in each group. The control group received conventional space maintainer, and the study group received personalized customized space maintainer. The dental arch space fftness, tooth alignment regularity, gingival health index and masticatory function were compared between the two groups. Results After treatment, the dental arch space fftness in the study group was better than that in the control group (P<0.05). After treatment, the tooth alignment regularity in the study group was better than that in the control group (P<0.05). After treatment, the gingival health index in the study group was better than that in the control group (P<0.05). After treatment, the masticatory efffciency, maximum occlusal force and subjective masticatory satisfaction in the study group were better than those in the control group (P<0.05). Conclusion Personalized customized space maintainer can improve dental arch space fftness and alignment in children with dentition defect, improve gingival health index, and enhance masticatory function.