title: Effect of light-curing units on the thermal expansion of resin nanocomposites.
abstract: OBJECTIVE
  To examine the thermal expansion of resin nanocomposites after light-curing using different light-curing units.
  
  
  METHODS
  Four different resin nanocomposites and four different light-curing units [quartz-tungsten-halogen (QTH), light emitting diode (LED), laser, and plasma arc] were chosen. Metal dies were filled with resin to make specimens and light-cured. The light intensity and light-curing time of the QTH and LED light-curing units were 1000 mW/cm2 and 40 seconds, 700 mW/cm2 and 40 seconds for the laser, and 1600 mW/cm2 and 3 seconds for the plasma arc. The coefficient of thermal expansion (CTE) was evaluated using a thermomechanical analyzer (TMA) at temperatures ranging from 30-80 degrees C.
  
  
  RESULTS
  The CTE of the resin nanocomposites tested ranged from 28.5 to 65.8 (x 10(-6)/ degrees C), depending on the product and type of light-curing unit used. Among the specimens, Grandio showed the lowest CTE. The specimens cured using the plasma arc unit (Apollo 95E) showed the highest CTE. There was a linear correlation between the CTE and filler content (vol%) (R: -0.94-0.99 depending on the light-curing unit). The results may suggest a careful selection of the light-curing unit because there was more expansion in the specimens cured using the plasma arc unit than those cured by the other units.
authors.affiliation: Department of Conservative Dentistry, College of Dentistry and Medical Research Institute, Pusan National University, Busan, Korea.
authors.forename: Jeong-Kil
authors.initials: JK
authors.lastname: Park
authors.forename: Bock
authors.initials: B
authors.lastname: Hur
authors.forename: Ching-Chang
authors.initials: CC
authors.lastname: Ko
authors.forename: Franklin
authors.initials: F
authors.lastname: García-Godoy
authors.forename: Hyung-Il
authors.initials: HI
authors.lastname: Kim
authors.forename: Yong Hoon
authors.initials: YH
authors.lastname: Kwon
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects; D055117:Curing Lights, Dental; D006358:Hot Temperature; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry / Q000528:radiation effects; D044366:Transition Temperature
chemical_list: D003188:Composite Resins