title: Effect of LED light-curing on the relative hardness of tooth-colored restorative materials.
abstract: OBJECTIVE
  To determine the relative hardness of GI-based restorative materials using both LED and QTH curing lights at different post-irradiation intervals.
  
  
  METHODS
  Four restorative materials (Z250, Beautifil, Dyract AP and Fuji II LC) with shade A3.5 were tested in conjunction with three LCUs (Astralis 3, Blue phase and Radii). The specimens were prepared using specially constructed molds, irradiating only the top surface to an equivalent energy density (J/CM). Vickers microhardness measurements were performed for both the top and bottom surfaces of all specimens following dry storage for 15 minutes in the dark. The measurements were repeated after 24 hours and 7 days. Mean VHNs and SD of the top and bottom surfaces of each specimen were calculated. Relative hardness values (RH) were also determined and mean RH was calculated for each group.
  
  
  RESULTS
  The top surface of the Z250, Beautifil and Dyract materials were significantly harder than the bottom surface (p < 0.05) with all LCUs and at all time intervals. Conversely, a different trend was observed with Fuji II LC, where bottom surface VHNs were significantly higher than top surface values (p < 0.05). Blue phase was the only LCU that recorded RH values above 80% for all tested material at all post-irradiation intervals.
  
  
  CONCLUSIONS
  A high-intensity LED LCU used for 10 seconds resulted in RH values greater than 80%, with all four restoratives tested indicating a sufficient degree of monomer conversion with such a short curing cycle.
authors.affiliation: Department of Operative Dentistry, Faculty of Dentistry, Cairo University, Cairo, Egypt.
authors.forename: Enas
authors.initials: E
authors.lastname: Mobarak
authors.forename: Iman
authors.initials: I
authors.lastname: Elsayad
authors.forename: Magdi
authors.initials: M
authors.lastname: Ibrahim
authors.forename: Wafa
authors.initials: W
authors.lastname: El-Badrawy
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D055117:Curing Lights, Dental / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003793:Dental Restoration, Permanent; D005899:Glass Ionomer Cements / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: C470433:Beautifil composite resin; D020770:Compomers; D003188:Composite Resins; D003764:Dental Materials; C088486:Dyract; C444701:Filtek Z250; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D019279:Resin Cements; D012117:Resins, Synthetic; D017438:Bisphenol A-Glycidyl Methacrylate