title: Effects of single-peak vs polywave light-emitting diode curing lights on the polymerization of resin cement.
abstract: OBJECTIVE
  This study examined the effect of selecting a single-peak blue vs a polywave blue/violet emission LED curing light on the degree of conversion (DC) and Knoop microhardness (KHN) of resin cements when light cured through a ceramic disk.
  
  
  METHODS
  Two shades (A1 and A4) of resin cement (Variolink II) were placed in a 0.5-mm-thick ring. The top surfaces were covered with a Mylar strip and further covered with a disk of 1-mm-thick Empress Esthetic ceramic, shade A2. The specimens were light cured by means of an Elipar-S10 (3M ESPE, single-peak blue LED) or BluePhase-G2 (Ivoclar Vivadent, polywave blue/violet LED) curing light, both for 20 s, directly on the surface of an attenuated total reflectance FT-IR plate at 30°C. The DC of the resin was calculated after 100 s. The specimens were removed, and the Knoop microhardness was tested immediately and again after 24-h storage in the dark at 37°C and 100% humidity. Five specimens were made in each group. The DC and Knoop microhardness results were analyzed with ANOVA and Fisher's PLSD at α = 0.05.
  
  
  RESULTS
  The choice of curing light had no significant effect on the DC and only a small effect on the immediate and 24-h KHN values. Shade A4 of the resin cement was harder and had a higher DC than shade A1.
  
  
  CONCLUSIONS
  When light cured for 20 s, Variolink II resin cement can be light cured with either the single-peak or the polywave curing light. Shade A4 of the cement was slightly harder than A1.
authors: Mohammed Q
authors: MQ
authors: AlQahtani
authors: Maan M
authors: MM
authors: AlShaafi
authors: Richard B
authors: RB
authors: Price
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D003116:Color; D055117:Curing Lights, Dental / Q000145:classification*; D003624:Darkness; D003776:Dental Porcelain / Q000737:chemistry; D006244:Hardness; D006801:Humans; D006813:Humidity; D055115:Light-Curing of Dental Adhesives / Q000295:instrumentation / Q000379:methods; D008422:Materials Testing; D055100:Optical Fibers; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; C075815:IPS-Empress ceramic; D019279:Resin Cements; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink