title: Effects of ceramic shade and thickness on the micro-mechanical properties of a light-cured resin cement in different shades.
abstract: OBJECTIVE
  The aim of this study was to evaluate the micro-mechanical properties of a light-cured resin cement in four different shades when polymerized through a leucite-reinforced glass-ceramic in different shades and thicknesses.
  
  
  METHODS
  A light-cured resin cement in four different shades (HV+1, HV+3, LV-1 and LV-3) was selected for this study. The specimens were cured by using a LED-unit (Bluephase®, IvoclarVivadent) for 20 s under a leucite-reinforced glass-ceramic (IPS Empress® CAD, IvoclarVivadent) in two different shades (A1 and A3) of different thicknesses (1 and 2 mm). Specimens cured directly, without an intermediate ceramic, served as control. The specimens were stored after curing for 24 h at 37°C by maintaining moisture conditions with distilled water. Micro-mechanical properties (indentation modulus, E; Hardness, HV; creep, Cr) of the resin cements were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). Twenty groups were included (n = 3), while 10 measurements were performed on each specimen. Data were statistically analyzed by using one-way ANOVA and Tukey's post-hoc test, as well as a multivariate analysis to test the influence of the study parameters.
  
  
  RESULTS
  Significant differences were observed between the micromechanical properties of the tested resin cements (p < 0.05). The resin cement shade showed the highest effect on the micromechanical properties (Partial-eta squared (ηP(2))-E = 0.45, ηP(2)-HV = 0.59, ηP(2)-Cr = 0.29) of the resin cement, followed by ceramic thickness (ηP(2)-E = 0.38, ηP(2)-HV = 0.3, ηP(2)-Cr = 0.04) and ceramic shade (ηP(2)-E = 0.2, ηP(2)-HV = 0.26).
  
  
  CONCLUSIONS
  Resin cement shade is an important factor influencing the mechanical properties of the material. Light shades of a resin cement express higher E and HV as well as lower Cr values compared with the darker ones.
authors: Department of Restorative Dentistry, Faculty of Dentistry, Hacettepe University , Ankara , Turkey.
authors: Elif
authors: E
authors: Öztürk
authors: Şükran
authors: Ş
authors: Bolay
authors: Reinhard
authors: R
authors: Hickel
authors: Nicoleta
authors: N
authors: Ilie
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003116:Color; D055117:Curing Lights, Dental / Q000145:classification; D003776:Dental Porcelain / Q000737:chemistry*; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000295:instrumentation; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D019279:Resin Cements; D014867:Water; D003776:Dental Porcelain; C078519:leucite; C023506:Glass ceramics
keywords: Light-cured resin cement; ceramic thickness; hardness; indentation modulus; micromechanical properties