title: Microhardness of resin composite materials light-cured through fiber reinforced composite.
abstract: OBJECTIVE
  To compare polymerization efficiency of resin composite basing materials when light-cured through resin composite and fiber reinforced composite (FRC) by testing microhardness.
  
  
  METHODS
  Simulated indirect restorations were prepared by application of resin composite (Clearfil AP-X) or FRC (EverStick) to nylon rings with 1.5mm thickness and 8mm diameter, followed by light-curing. Resin composite basing material (Clearfil Majesty Flow or Clearfil AP-X) was applied to identical rings and light-cured through the simulated indirect restorations with exposure times of 20, 40, or 60s. Light-curing though a ring without resin material (=no indirect restoration) served as control. For each combination of basing material and indirect restoration 10 specimens were prepared for each exposure time. Top and bottom surface Vickers microhardness numbers (VHNs) of basing materials were recorded after 24h.
  
  
  RESULTS
  After 60s exposure time, VHNs with indirect FRC were not different from control VHNs, while VHNs with indirect resin composite were significantly lower (p<0.001). Linear regression analysis revealed that resin composite basing material used had the greatest effect on top and bottom VHNs (p<0.001). The presence of an indirect restoration resulted in decreased VHNs (p<0.001), with resin composite resulting in lower VHNs when compared to FRC. Moreover, a longer exposure time resulted in increased VHNs (p<0.001).
  
  
  CONCLUSIONS
  Results suggest that polymerization of resin composite basing materials is more effective when light-curing through an FRC than through a resin composite indirect restoration. Prolonging of exposure time, however, is necessary when compared to light-curing without presence of indirect restoration material.
authors.affiliation: Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. w.fennis@dent.umcn.nl
authors.forename: Willem M M
authors.initials: WM
authors.lastname: Fennis
authors.forename: Noel J
authors.initials: NJ
authors.lastname: Ray
authors.forename: Nico H J
authors.initials: NH
authors.lastname: Creugers
authors.forename: Cees M
authors.initials: CM
authors.lastname: Kreulen
mesh_terms: D003188:Composite Resins / Q000528:radiation effects*; D003799:Dental Stress Analysis; D006244:Hardness; D007284:Inlays; D055115:Light-Curing of Dental Adhesives; D016014:Linear Models; D008422:Materials Testing; D008689:Methacrylates / Q000528:radiation effects; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D013997:Time Factors
chemical_list: C112828:Clearfil AP-X; D003188:Composite Resins; D008689:Methacrylates; D019279:Resin Cements; C541508:clearfil majesty; C496140:everStick