Space maintainers needs following extraction of primary molars, due to severe dental caries under general anesthesia. Delivery of conventional space maintainers has three of the disadvantages of the method, there being a impression taking and time consuming due to laboratory procedure, and delivery problem due to relaxed tongue. For this problem improved, modified space maintainer is prefabricated before procedure, and adjust, delivery in operation room, favorable results were obtained. The following results were obtained. 1. Delivery time is very reduced than conventional space maintainers. 2. After space maintainer delivery, follow check-up, without impingement of soft tissue, distortion of wire. After space maintainer delivery, continuous research is required so that space maintainer delivery is applied to usual dental treatment, and it is necessary of long term research.