title: Influence of the light curing tip distance and material opacity on selected physical properties of a pit and fissure sealant.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the influence of the light curing tip distance and material opacity on hardness (KHN), degree of conversion (DC), and crosslink density (CLD) of a resin-based fissure sealant (Fluroshield).
  
  
  METHODS
  One-millimeter-thick  white opaque and clear sealant specimens, photoactivated at 1-, 2-, and 3-mm distances, were fabricated (8 groups, N=5). KHN and DC were evaluated 24 hours after polymerization. Specimens were subjected to a new KHN reading after 24-hour immersion in absolute ethanol to indirectly assess the  CLD.
  
  
  RESULTS
  Samples of clear sealant cured at longer distances presented lower KHN, although there were not differences between opacities at all distances. The mean DC of the opaque white material, however, was lower than that of the clear one at higher distances. There were no differences  among CLD for all experimental conditions analyzed.
  
  
  CONCLUSIONS
  KHN of the clear sealant was affected by increased distances. The clear sealant showed higher DC at increased distances, although CLD was not influenced by the factors under study. Since physical properties of sealing  materials are directly related to their clinical efficacy, the clear sealant tested may present a better clinical performance than the opaque one.
authors.affiliation: Piracicaba Dental School, State University of Campinas, Piracicaba, São Paulo, Brazil. boniek.castillo@gmail.com
authors.forename: Boniek
authors.initials: B
authors.lastname: Castillo Dutra Borges
authors.forename: Paulo
authors.initials: P
authors.lastname: Roger Pinho de Silva
authors.forename: Anderson
authors.initials: A
authors.lastname: Catelan
authors.forename: Flávio
authors.initials: F
authors.lastname: Henrique Baggio Aguiar
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055598:Chemical Phenomena; D055117:Curing Lights, Dental; D004867:Equipment Design; D000431:Ethanol / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008027:Light; D055668:Photochemical Processes; D010895:Pit and Fissure Sealants / Q000737:chemistry*; D058105:Polymerization; D011140:Polyurethanes / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
chemical_list: D010895:Pit and Fissure Sealants; D011140:Polyurethanes; D012997:Solvents; C086661:Fluoroshield; D000431:Ethanol; D017438:Bisphenol A-Glycidyl Methacrylate