title: Effect of light curing unit on resin-modified glass-ionomer cements: a microhardness assessment.
abstract: OBJECTIVE
  To evaluate the microhardness of resin-modified glass-ionomer cements (RMGICs) photoactivated with a blue light-emitting diode (LED) curing light.
  
  
  METHODS
  Thirty specimens were distributed in 3 groups: Fuji II LC Improved/GC (RM1), Vitremer/3M ESPE (RM2) and Filtek Z250/3M ESPE (RM3). Two commercial light-curing units were used to polymerize the materials: LED/Ultrablue IS and a halogen light/XL3000 (QTH). After 24 h, Knoop microhardness test was performed. Data were submitted to three-way ANOVA and Tukey's test at a pre-set alpha of 0.05.
  
  
  RESULTS
  At the top surface, no statistically significant difference (p>0.05) in the microhardness was seen when the LED and QTH lights were used for all materials. At the bottom surface, microhardness mean value of RM2 was significantly higher when the QTH light was used (p<0.05). For RM1, statistically significant higher values (p<0.05) were seen when the LED light was used. No statistically significant difference (p>0.05) was seen at the bottom surface for RM3, irrespective of the light used. Top-to-bottom surface comparison showed no statistically significant difference (p>0.05) for both RMGICs, regardless of the light used. For RM3, microhardness mean value at the top was significantly higher (p<0.05) than bottom microhardness when both curing units were used.
  
  
  CONCLUSIONS
  The microhardness values seen when a LED light was used varied depending on the restorative material tested.
authors.affiliation: Department of Operative Dentistry, University North of Paraná, Londrina, PR, Brazil. dcefaly@uol.com.br
authors.forename: Daniela Francisca Gigo
authors.initials: DF
authors.lastname: Cefaly
authors.forename: Liliam Lucia Carrara Paes
authors.initials: LL
authors.lastname: de Mello
authors.forename: Linda
authors.initials: L
authors.lastname: Wang
authors.forename: José Roberto Pereira
authors.initials: JR
authors.lastname: Lauris
authors.forename: Paulo Henrique Perlatti
authors.initials: PH
authors.lastname: D'Alpino
mesh_terms: D003188:Composite Resins / Q000528:radiation effects; D055117:Curing Lights, Dental; D005899:Glass Ionomer Cements / Q000737:chemistry / Q000528:radiation effects*; D006219:Halogens; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D012117:Resins, Synthetic / Q000528:radiation effects; D012666:Semiconductors; D013499:Surface Properties
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D006219:Halogens; D012117:Resins, Synthetic; C084550:Vitremer