title: Depth of cure of resin-modified glass ionomers.
abstract: OBJECTIVE
  The cure of all resin-modified glass ionomer materials depends to some degree on light activation. However, the materials have chemical-cure mechanisms that could increase depth of cure. Thus, this study was conducted to evaluate the depth of cure of five resin-modified glass ionomer restorative materials.
  
  
  METHODS
  Five specimens of Fuji II LC (GC America), Geristore (Den-Mat), Photac-Fil (ESPE America), VariGlass (Caulk/Dentsply), and Vitremer (3M Dental Products) were fabricated in Teflon molds. Each material was visible light-activated for 40 s. Specimens were 5 mm x 5 mm x 9 mm (depth), but material at depths greater than 5 mm was too soft to measure. Microhardness (KHN) at the surface and at 1 mm increments below the surface of each specimen was measured at 10 min, 1 d, and 7 d after light-curing.
  
  
  RESULTS
  At 10 min post-irradiation, the top layers (0-1 mm) of each material were significantly harder than the deeper layers (4-5 mm). However, at 1 d, Geristore, Photac-Fil, Vitremer and Fuji II LC had uniform hardness, regardless of depth. In contrast, VariGlass hardness decreased significantly with depth, from 43.3 at the surface to 11.7 at 5 mm. At 7 d, Photac-Fil, Vitremer and Fuji II LC had more uniform hardness regardless of depth than either Geristore or VariGlass. Data were analyzed using ANOVA and Duncan's multiple range tests.
  
  
  CONCLUSIONS
  Immediately following light activation, the upper layers of each material were harder than the deeper layers, but the degree of cure in the deeper layers improved over time. VariGlass was the only material in which bottom hardness (5mm) and top hardness remained significantly different at 1 d, suggesting that VariGlass has less effective chemical-cure mechanisms than the other materials tested.
authors.affiliation: Department of Operative Dentistry, The University of North Carolina, Chapel Hill, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Swift
authors.forename: M A
authors.initials: MA
authors.lastname: Pawlus
authors.forename: M A
authors.initials: MA
authors.lastname: Vargas
authors.forename: D
authors.initials: D
authors.lastname: Fortin
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D008422:Materials Testing; D012117:Resins, Synthetic / Q000737:chemistry; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; C079765:Fuji II LC cement; C074933:Geristore; D005899:Glass Ionomer Cements; C081144:Photac-Fil; D012117:Resins, Synthetic; C081982:VariGlass VLC; C084550:Vitremer