S-PRG Containing Paste in Enamel Remineralization after Bracket Removal.

Objectives: After removal of the orthodontic bracket, residual bonding material must be cleaned up and then the remineralization of resin-infiltrated and etched enamels should be enhanced. Surface Pre-Reacted Glass-ionomer (S-PRG) technology, forming stable glass-ionomer phase in fillers, was introduced recently and the S-PRG fillers show the ability to release multiple ions. The purpose of this study was to determine if new paste containing S-PRG filler can accelerate the remineralization of enamel surface after removal of the bracket.
Methods: Surfaces of polished human enamel were etched with 35% phosphoric acid and then subdivided into two regions. Bracket bonding resin (Blueglue, Ormco) was thinly applied on one region and irradiated. After 24h immersion in artificial saliva, the bonding resin was removed by grinding with low-speed tungsten carbide bur, followed by polishing with four different polishing systems: 1), nonfluoridated paste (Pressage; Shofu), 2), fluoridated paste (Merssage; Shofu), 3), S-PRG filler-containing paste (PRG CompoGloss, Shofu), 4), Pressage plus PRG CompoGloss paste (Shofu) (n=15). The polished specimens were then immersed in an artificial saliva solution for seven days at 37°C. Nanoindentation testing of enamel surfaces was carried out (ENT-1100a, ELIONIX) using two loading conditions (10, and 100 mN). Mean values for hardness and elastic modulus were compared using ANOVA and Tukey’s test.
Results: For all specimens, their mechanical properties of enamel surfaces decreased markedly by acid etching. Right after bonding resin removal, resin-infiltrated enamel showed greater mechanical properties compared to the etched enamel surface. After polishing and seven days immersion, recovery of the mechanical properties for both regions (resin-infiltrated and etched enamels) were progressed. By polishing with S-PRG fillercontaining paste plus nonfluoridated paste, the mechanical properties were significantly recovered and the remineralization ability was equivalent with fluoridated paste.
Conclusions: Polishing using S-PRG filler-containing and nonfluoridated pastes can help enamel remineralization after bracket removal.