title: Effectiveness of light emitting diode and halogen light curing units for curing microhybrid and nanocomposites.
abstract: OBJECTIVE
  To compare the polymerization efficacy of micro-hybrid and nanocomposites cured with Quartz-tungsten halogen (QTH) and light emitting diode (LED) light curing units (LCUs). The effectiveness of pulse cure mode in LED LCU was also investigated.
  
  
  METHODS
  Both micro-hybrid and nanocomposite specimens were cured using four different curing protocols giving a total of eight experimental groups. Ten cylindrical specimens were prepared for each group, and light cured for 40 s on the top surface, thus giving a total of eighty specimens. Vicker hardness measurements were carried out on the top and bottom surfaces after 24 h and hardness ratio was calculated.
  
  
  RESULTS
  For both micro-hybrid and nanocomposites, highest mean VHN was observed for the group cured with QTH LCU, and the lowest was observed for the group cured with second LED LCU in standard mode but the difference was significant only in case of nanocomposite.
  
  
  CONCLUSIONS
  Curing nanocomposites with QTH LCU results in better micro hardness. Pulse cure mode does not effectively increase polymerization efficacy than the standard mode of curing.
authors.affiliation: Department of Pedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University, Mangalore, Karnataka, India.
authors.forename: Shwetha
authors.initials: S
authors.lastname: Choudhary
authors.forename: Bs
authors.initials: B
authors.lastname: Suprabha
keywords: Curing lights; hardness; nanocomposite