title: Surface hardness of light-activated resin composites cured by two different visible-light sources: an in vitro study.
abstract: OBJECTIVE
  Microhardness values of upper and lower surfaces of disk specimens of 3 commercially available resin composites were compared and cured using both the traditional halogen source and a plasma arc lamp.
  
  
  METHODS
  Twenty samples of each of the resin composites were cured in nylon washers. Ten samples of each composite were cured using the appropriate halogen lamp protocol, and 10 samples of each were cured using the plasma lamp protocol. Surface microhardness measurements were carried out using a calibrated Vickers indenter on both top and bottom surfaces after 7 days of storage in air at 20 degrees C. Statistical analysis of the data was carried out using a commercial statistical package. The data for top and bottom surfaces were analyzed separately using a repeated measures analysis of variance (ANOVA).
  
  
  RESULTS
  Lamp, composite, and the interaction between lamp and composite were significant in determining the results for both top and bottom surfaces of the disk-shaped specimens. The plasma lamp yielded lower hardness values for all surfaces compared with the halogen source, but the size of the difference depended on the composite.
  
  
  CONCLUSIONS
  Caution must be exercised in the plasma irradiation of resin composites as a curing method due to the possibility of reduced surface microhardness values that may reflect a reduced percent conversion of monomer to polymer.
authors.affiliation: Department of Restorative Dentistry, University Dental School and Hospital, National University of Ireland, Cork, Ireland.
authors.forename: S
authors.initials: S
authors.lastname: Sharkey
authors.forename: N
authors.initials: N
authors.lastname: Ray
authors.forename: F
authors.initials: F
authors.lastname: Burke
authors.forename: H
authors.initials: H
authors.lastname: Ziada
authors.forename: A
authors.initials: A
authors.lastname: Hannigan
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects*; D006244:Hardness; D008027:Light; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties; D013674:Technology, Dental / Q000379:methods; D013997:Time Factors
chemical_list: D003188:Composite Resins; D019279:Resin Cements; C065770:Herculite XR; C074741:Silux Plus