title: Effect of ceramic thickness and shade on mechanical properties of a resin luting agent.
abstract: OBJECTIVE
  This study aimed to investigate the influence of ceramic thickness and shade on the Knoop hardness and dynamic elastic modulus of a dual-cured resin cement.
  
  
  METHODS
  Six ceramic shades (Bleaching, A1, A2, A3, A3.5, B3) and two ceramic thicknesses (1 mm, 3 mm) were evaluated. Disk specimens (diameter: 7 mm; thickness: 2 mm) of the resin cement were light cured under a ceramic block. Light-cured specimens without the ceramic block at distances of 1 and 3 mm were also produced. The Knoop hardness number (KHN), density, and dynamic Young's moduli were determined. Statistical analysis was conducted using ANOVA and a Tukey B rank order test (p = 0.05).
  
  
  RESULTS
  The bleaching 1-mm-thick group exhibited significantly higher dynamic Young's modulus. Lower dynamic Young's moduli were observed for the 3-mm-thick ceramic groups compared to bleaching 3-mm-thick group, and no difference was found among the other 3-mm groups. For the KHN, when A3.5 3-mm-thick was used, the KHN was significantly lower than bleaching and A1 1-mm-thick ceramic; however, no difference was exhibited between the thicknesses of the same shade.
  
  
  CONCLUSIONS
  The dual-cured resin cement studied irradiated through the 1-mm-thick ceramic with the lightest shade (bleaching ceramic) exhibited a better elastic modulus, and there was no effect in KHN of the resin cement when light cured under different ceramic shades and thicknesses (1 and 3 mm), except when the A3.5 3-mm-thick ceramic was used.
  
  
  CONCLUSIONS
  Variolink II irradiated through ceramic with the lowest chroma exhibited the highest elastic modulus; therefore, the light activation method might not be the same for all clinical situations.
authors.affiliation: School of Dentistry, University of Alberta, Edmonton, Canada.
authors.forename: Sheila Pestana
authors.initials: SP
authors.lastname: Passos
authors.forename: Estevão Tomomitsu
authors.initials: ET
authors.lastname: Kimpara
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Bottino
authors.forename: Amin S
authors.initials: AS
authors.lastname: Rizkalla
authors.forename: Gildo Coelho
authors.initials: GC
authors.lastname: Santos
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003776:Dental Porcelain / Q000737:chemistry*; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D055116:Self-Curing of Dental Resins; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D019279:Resin Cements; D003776:Dental Porcelain; C103502:Variolink
keywords: Dual-cured resin luting agent; dynamic elastic modulus; microhardness