title: Effect of different light curing units on Knoop hardness and temperature of resin composite.
abstract: OBJECTIVE
  To evaluate the influence of quartz tungsten halogen and plasma arc curing (PAC) lights on Knoop hardness and change in polymerization temperature of resin composite.
  
  
  METHODS
  Filtek Z250 and Esthet X composites were used in the shade A3. The temperature increase was registered with Type-k thermocouple connected to a digital thermometer (Iopetherm 46). A self-cured polymerized acrylic resin base was built in order to guide the thermocouple and to support the dentin disk of 1.0 mm thickness obtained from bovine tooth. On the acrylic resin base, elastomer mold of 2.0 mm was adapted. The temperature increase was measured after composite light curing. After 24 h, the specimens were submitted to Knoop hardness test (HMV-2000, Shimadzu, Tokyo, Japan). Data were submitted to ANOVA and Tukey's test (alpha = 0.05).
  
  
  RESULTS
  For both composites, there were no significant differences (P > 0.05) in the top surface hardness; however, PAC promoted statistically lower (P < 0.05) Knoop hardness number values in the bottom. The mean temperature increase showed no significant statistical differences (P > 0.05).
  
  
  CONCLUSIONS
  The standardized radiant exposure showed no influence on the temperature increase of the composite, however, showed significant effect on hardness values.
authors.affiliation: Pythagoras College, Belo Horizonte MG, Brazil. rickdanil@fop.unicamp.br
authors.forename: Ricardo Danil
authors.initials: RD
authors.lastname: Guiraldo
authors.forename: Simonides
authors.initials: S
authors.lastname: Consani
authors.forename: Rafael Leonardo
authors.initials: RL
authors.lastname: Xediek Consani
authors.forename: Wilson Batista
authors.initials: WB
authors.lastname: Mendes
authors.forename: Thais
authors.initials: T
authors.lastname: Lympius
authors.forename: Mario Alexandre
authors.initials: MA
authors.lastname: Coelho Sinhoreti
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D055117:Curing Lights, Dental / Q000145:classification / Q000592:standards*; D003743:Dental Enamel / Q000187:drug effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003793:Dental Restoration, Permanent / Q000592:standards; D006244:Hardness / Q000528:radiation effects*; D006358:Hot Temperature; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D012016:Reference Values; D018709:Statistics, Nonparametric
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C466112:Esthet-X; C444701:Filtek Z250