title: Influence of light intensity on two restorative systems.
abstract: OBJECTIVE
  High intensity curing lights are recommended almost universally on the basis of immediate curing depth measurements. Although this single factor is well documented, the influence of light intensity on other parameters has not been investigated extensively.
  
  
  METHODS
  Two restorative systems were examined with two light intensities in regard to four properties; polymerization shrinkage (density method), flexural modulus and strength (ISO 4049), hardness profiles after post-cure (Vickers), and marginal adaptation in dentine cavities (quantitative margin analysis).
  
  
  RESULTS
  The variation in light intensity did not significantly affect curing contraction or post-cure hardness profiles to a depth of 4.5 mm for either resin composite. Significant differences were found in flexural modulus with both restoratives; only one material demonstrated a light intensity-related influence on flexural strength. Marginal gap formation increased in each bonding agent/resin composite pair with increased light intensity.
  
  
  CONCLUSIONS
  In clinically relevant layer thicknesses, curing a resin composite with a higher intensity light may demonstrate significant disadvantages due to increased shrinkage stress.
authors.affiliation: Clinical Research Department, Ivoclar/Vivadent, Schaan, Principality of Liechtenstein.
authors.forename: G L
authors.initials: GL
authors.lastname: Unterbrink
authors.forename: R
authors.initials: R
authors.lastname: Muessner
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003804:Dentin; D017220:Dentin-Bonding Agents; D004548:Elasticity; D006244:Hardness; D006245:Hardness Tests; D008027:Light; D008422:Materials Testing; D019279:Resin Cements; D012822:Silicon Dioxide / Q000737:chemistry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D015040:Zirconium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C078484:Syntac dentine adhesive; C090969:Tetric; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium