title: Effect of resin-modified glass ionomer containing bioactive glass on the flexural strength and morphology of demineralized dentin.
abstract: BACKGROUND
  Recently, bioactive materials have been incorporated into glass ionomer cements to promote the precipitation of calcium phosphates in surrounding tooth structures. This in vitro study was undertaken to evaluate the effect of resin-modified glass ionomer (RMGI) containing bioactive glass (RMGI-BAG) on the flexural strength (FS) of demineralized dentin.
  
  
  METHODS
  A total of 120 dentin bars (2×2×6 mm) were prepared from sound human third molars. Of these, 60 bars were immersed in a demineralizing solution for 96 hours. This produced dentin in two demineralization conditions (DC): untreated and demineralized. Each dentin bar was immersed for 14 days in simulated body fluid (SBF) at 37°C. Three immersion conditions (IC) were investigated: IC1-SBF only; IC2-SBF + an RMGI bar; IC3-SBF + an RMGI-BAG bar. The combination of the DCs and ICs produced six groups (n=20). FS values of the specimens were measured using a three-point bending test. The microstructural changes and the elemental contents of dentin surfaces were evaluated by scanning electron microscopy. Data were analyzed using a two-way analysis of variance (ANOVA) for the effects of the two independent variables, ie, DC and IC, on mean flexural strength. Tukey multiple comparison tests and simple main effects models were used as needed. The significance level of all tests was set at α=0.05.
  
  
  RESULTS
  Both DC (p=0.001) and IC (p=0.049) significantly influenced FS (two-way ANOVA). The interaction between DC and IC did not significantly affect FS (p=0.36). For undemineralized dentin, IC did not affect the mean FS (simple main effects model; p=0.4). However, for demineralized dentin, IC significantly affected FS (small main effects model; p=0.008). The Tukey test showed that for demineralized dentin, the mean FS produced by immersion in SBF + RMGI-BAG was significantly stronger than that produced by either immersion in SBF only (p=0.011) or in SBF + RMGI (p=0.034). Scanning electron microscope/energy-dispersive x-ray spectroscopy analyses revealed more calcium and phosphate ions on the surface of dentin immersed in SBF + RMGI-BAG than on dentin immersed in SBF + RMGI.
  
  
  CONCLUSIONS
  Immersion in SBF + RMGI-BAG increased the FS of demineralized dentin more than immersion in SBF + RMGI.
authors.affiliation: Dental Materials Research Center and Department of Operative Dentistry, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran. khoroushi@dnt.mui.ac.ir
authors.forename: M
authors.initials: M
authors.lastname: Khoroushi
authors.forename: S-M
authors.initials: SM
authors.lastname: Mousavinasab
authors.forename: F
authors.initials: F
authors.lastname: Keshani
authors.forename: Shirin
authors.initials: S
authors.lastname: Hashemi
mesh_terms: D000704:Analysis of Variance; D001826:Body Fluids; D002516:Ceramics / Q000494:pharmacology*; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D005899:Glass Ionomer Cements / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability / Q000187:drug effects*; D018709:Statistics, Nonparametric; D017001:Tooth Demineralization
chemical_list: C022107:Bioglass; D005899:Glass Ionomer Cements