Objectives. The objective of this study was to develop a resin-based pit and fissure sealant incorporating 45S5 bioactive glass (BAG), which exhibits a self-marginal sealing potential by forming hydroxyapatite, and to assess its chemical properties and apatite formation. Materials and Methods. Experimental materials were prepared by adding 45S5 BAG to the resin matrix at concentrations of 0 (control), 12.5, 37.5, and 50 wt.%. Ion release, pH variation, and apatite formation (raman spectrometer and scanning electron microscopy–energy-dispersive X-ray spectrometry measurements) were analyzed. Results. The control group did not release any ions, while the experimental groups showed an increased release of Ca and P ions with higher concentrations of 45S5 BAG. The pH of the experimental groups remained consistently high. The 50 wt.% BAG group exhibited the formation of apatite peaks for a duration of 90 days. Additionally, a layer of apatite composed of Ca and P was precipitated on the surface and cross-section. Conclusions. This study suggests that a resin-based pit and fissure sealant containing 45S5 BAG can self-seal under microleakage between the tooth and restorative material. Therefore, the results of this study provide fundamental information that will be useful for the future development of resin-based pit and fissure sealants with long-term self-healing effects. Clinical Relevance. The resin-based pit and fissure sealant containing 45S5 BAG is a promising material for its apatite-forming ability for enamel remineralization.