title: Effect of three nanobiomaterials on microhardness of bleached enamel.
abstract: OBJECTIVE
  The aim of this in vitro study was to evaluate the effect of incorporating three different nanobiomaterials into bleaching material on microhardness of bleached enamel.
  
  
  METHODS
  The crowns of 24 extracted sound human molars were sectioned. Sixty enamel specimens (2 × 3 × 4 mm) were selected and divided into five groups (n = 12): Group 1 received no bleaching procedure (control); Group 2 underwent bleaching with a 40% hydrogen peroxide (HP) gel; Groups 3, 4, and 5 were bleached with a 40% HP gel modified by incorporation of bioactive glass (BAG), amorphous calcium phosphate (ACP) and hydroxyapatite (HA), respectively. The enamel microhardness was evaluated. The differences in Knoop microhardness data of each group were analyzed by one-way ANOVA, followed by post hoc Tukey tests.
  
  
  RESULTS
  Significant differences were observed between the study groups. The enamel microhardness changes in Groups 1, 3, 4, and 5 were significantly lower than that of Group 2 (p < 0.001).
  
  
  CONCLUSIONS
  Within the limitations of this study, it can be concluded that incorporation of each one of the three tested biomaterials as remineralizing agents might be effective in decreasing enamel microhardness changes subsequent to in-office bleaching.
authors: Dental Materials Research Center, Department of Operative Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors: Maryam
authors: 0000-0003-2743-2631
authors: M
authors: Khoroushi
authors: Dental Research Center and Department of Orthodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors: Farinaz
authors: 0000-0003-4869-7794
authors: F
authors: Shirban
authors: Department of Operative Dentistry, School of Dentistry, Semnan University of Medical Sciences, Semnan, Iran.
authors: Sara
authors: S
authors: Kaveh
authors: Persian Gulf Oral and Dental Disease Research Center, Hormozgan University of Medical Sciences, Bandar Abbas, Iran.
authors: Samaneh
authors: S
authors: Doustfateme
keywords: Amorphous calcium phosphate; Bioactive glass; Bleaching; Enamel; Hardness; Hydroxyapatite