Hypophosphatasia is a rare inherited disorder characterized by defective bone mineralization and deficiency of tissue non-specific alkaline phosphatase (TNSALP) activity. The disease is caused by mutations in the liver/bone/kidney alkaline phosphatase gene (ALPL) encoding TNSALP. As for dental manifestations, premature loss of deciduous teeth due to disturbed cementum formation is well known. However, few reports of multiple cases have been presented. The oral manifestations of patients diagnosed with hypophosphatasia were analyzed by collecting clinical records of cases from a nationwide survey of pediatric dentistry clinics affiliated with 29 university dental hospitals in Japan. We inquired regarding the number of cases and clinical findings of diagnosed patients. We obtained information for 9 children diagnosed with hypophosphatasia from our university and 10 from 6 other universities. The main oral manifestation was early exfoliation of deciduous teeth, which was found in 15 of the 19 cases. Early exfoliation of mandibular deciduous anterior teeth was recognized in 14, whereas there were no cases of early exfoliation of a permanent tooth. The main oral finding of hypophosphatasia was early exfoliation of deciduous teeth, predominantly in the mandibular anterior region of children aged 1 to 4 years old.