Effects of polishing with paste containing surface pre-reacted glass-ionomer fillers on enamel remineralization after orthodontic bracket debonding

Surface pre-reacted glass-ionomer (S-PRG) technology allows for the release of multiple ions. This study was performed to investigate the remineralization of etched enamel after removal of the bracket using a novel paste containing S-PRG filler. Surfaces of polished enamel were etched with phosphoric acid and then subdivided into two regions. Bracket bonding resin was thinly applied to one region. After 24-hr immersion in artificial saliva, the bonding resin on the enamel surfaces was removed by grinding with tungsten carbide bur at low-speed, followed by polishing with one of four different polishing systems: (a) nonfluoridated paste (NF); (b) fluoridated paste (F); (c) S-PRG filler-containing paste (S-PRG); or (d) nonfluoridated plus S-PRG filler-containing paste (NF + S-PRG) (n = 15). The polished specimens were then immersed in an artificial saliva solution for 7 days. Nanoindentation testing of enamel surfaces was performed and their mechanical properties were compared. Representative specimens were examined with scanning electron microscope. In all specimens, the mechanical properties of the enamel surfaces were markedly degraded by acid etching. However, the mechanical properties of both regions (etched and resin-infiltrated enamels) showed recovery after polishing and 7-day immersion. Polishing with NF + S-PRG paste led to significant recovery of mechanical properties compared to polishing with NF or S-PRG paste alone, and remineralization was equivalent to that seen with F paste. Porous etched enamel surfaces were filled with a remineralization layer after each polishing procedure and 7-day immersion in all polishing groups. Polishing using NF + S-PRG paste can facilitate enamel remineralization after bracket removal.