In the oral environment, teeth are exposed to periods of demineralization as well as remineralization. Considering the evolution of the bonded restorations, there was a challenge bonding to a questionable tooth substrate. Bioactive glasses are used widely in dentistry nowadays with its different formulations and particle sizes. Making use of the Nano technology; Nano bioactive glass was compared in the remineralization capacity to conventional bioactive glass. Self etch adhesives were used to allow bonding to the tooth substrates with minimal intervention with the mineral content of the teeth. This study was designed to evaluate the Micro shear bond strength of Nano-filled resin composite, bonded by self-etch adhesive to remineralized enamel and dentin using conventional and Nano bioactive glass versus demineralized enamel and dentin. Forty teeth were used; enamel and dentin specimens were derived from each tooth, producing 80 specimens (40 for enamel and 40 for dentin). Regarding the enamel substrate, 5 specimens were used as a positive control (sound enamel), while the remaining 35 specimens were demineralized. The demineralized enamel was divided by which, 5 specimens acted as negative control (demineralized enamel) and the remaining 30 specimens were divided into two main groups (15 each) according to the remineralizing agent to be used, either conventional or Nano bioactive glass. Each group was subdivided into 3 subgroups (5 each) according to the period of application of the remineralizing agent used, one day, one week and one month. Regarding the dentin substrate, 5 specimens were used as a positive control (sound dentin), while the remaining 35 specimens were demineralized. The demineralized dentin was divided by which, 5 specimens acted as negative control (demineralized dentin) and the remaining 30 specimens were divided into two main groups (15 each) according to the remineralizing agent to be used, either conventional or Nano bioactive glass. Each group was subdivided into 3 subgroups (5 each) according to the period of application the remineralizing agent used, one day, one week and one month.