title: Effect of a broad-spectrum LED curing light on the Knoop microhardness of four posterior resin based composites at 2, 4 and 6-mm depths.
abstract: OBJECTIVE
  To measure the Knoop microhardness at the bottom of four posterior resin-based composites (RBCs): Tetric EvoCeram Bulk Fill (Ivoclar Vivadent), SureFil SDR flow (DENTSPLY), SonicFill (Kerr), and x-tra fil (Voco).
  
  
  METHODS
  The RBCs were expressed into metal rings that were 2, 4, or 6-mm thick with a 4-mm internal diameter at 30°C. The uncured specimens were covered by a Mylar strip and a Bluephase 20i (Ivoclar Vivadent) polywave(®) LED light-curing unit was used in high power setting for 20s. The specimens were then removed and placed immediately on a Knoop microhardness-testing device and the microhardness was measured at 9 points across top and bottom surfaces of each specimen. Five specimens were made for each condition.
  
  
  RESULTS
  As expected, for each RBC there was no significant difference in the microhardness values at the top of the 2, 4 and 6-mm thick specimens. SureFil SDR Flow was the softest resin, but was the only resin that had no significant difference between the KHN values at the bottom of the 2 and 4-mm (Mixed Model ANOVA p<0.05). Although the KHN of SureFil SDR Flow was only marginally significantly different between the 2 and 6-mm thickness, the bottom at 6-mm was only 59% of the hardness measured at the top.
  
  
  CONCLUSIONS
  This study highlights that clinicians need to consider how the depth of cure was evaluated when determining the depth of cure. SureFil SDR Flow was the softest material and, in accordance with manufacturer's instructions, this RBC should be overlaid with a conventional resin.
authors.affiliation: King Saud University, Restorative Dental Sciences, P.O. Box 60169, Riyadh 11545, Saudi Arabia.
authors.forename: Maan M
authors.initials: MM
authors.lastname: ALShaafi
authors.affiliation: Dental Clinical Sciences, Dalhousie University, P.O. Box 15000, Halifax, NS B3H4R2, Canada; University of Bonn-Rhein-Sieg, Applied Sciences, Department of Natural Sciences, von-Liebig-Strasse 20, 53359 Rhinebach, Germany; Tomas Bata University in Zlín, Faculty of Technology, náměstí T. G. Masaryka 275, 76272 Zlín, Czech Republic.
authors.forename: Thomas
authors.initials: T
authors.lastname: Haenel
authors.affiliation: Dental Clinical Sciences, Dalhousie University, P.O. Box 15000, Halifax, NS B3H4R2, Canada.
authors.forename: Braden
authors.initials: B
authors.lastname: Sullivan
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, P.O. BOX 15000, Halifax, NS B3H 4R2, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Labrie
authors.affiliation: King Saud University, Restorative Dental Sciences, P.O. Box 60169, Riyadh 11545, Saudi Arabia.
authors.forename: Mohammed Q
authors.initials: MQ
authors.lastname: Alqahtani
authors.affiliation: Dental Clinical Sciences, Dalhousie University, P.O. Box 15000, Halifax, NS B3H4R2, Canada. Electronic address: rbprice@Dal.ca.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Price
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects*; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects; D055117:Curing Lights, Dental; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects*; D003799:Dental Stress Analysis; D055115:Light-Curing of Dental Adhesives / Q000295:instrumentation / Q000379:methods; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D058105:Polymerization / Q000528:radiation effects; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D003764:Dental Materials; C090257:Foundation composite resin; D008689:Methacrylates; D011140:Polyurethanes; C000613185:SonicFill; C553871:Surefil SDR Flow; C501891:Tetric EvoCeram; C513703:Vivadent; C529733:X-tra fil composite resin; D017438:Bisphenol A-Glycidyl Methacrylate
keywords: Broad spectrum LED curing light; Bulk fill resin based composites; Depth of cure; Knoop microhardness