title: Effect of stepped exposure on quantitative in vitro marginal microleakage.
abstract: OBJECTIVE
  The aim of this in vitro study was to evaluate the effect of a soft-start curing mode on microleakage
  
  
  METHODS
  Standardized Class V cavities were prepared within all the margins in the buccal enamel or dentin surface of sound, freshly extracted inferior bovine incisors. Forty preparations were filled with a restorative system (Single Bond and Filtek Z250, 3M ESPE, St. Paul, MN, USA). Ten restorations of each group were made on both types of substrates and polymerized with a conventional curing technique (600 mW/cm2/40 s) or with a soft-start technique (150 mW/cm2/10 s + 600 mW/cm2/30 s). All specimens were thermocycled 3000 times and then immersed in methylene blue 2% for 12 hours. The specimen microleakage was quantitatively determined in a spectrophotometer.
  
  
  RESULTS
  The soft-start technique resulted in statistically significant less microleakage for each substrate (p < .05). The conventional groups exhibited 6.1 (dentin) to 15.4% (enamel) more leakage compared with the soft-start groups. When compared with the enamel margins, the dentin margins demonstrated greater microleakage: from 15.5% greater with the conventional light-curing mode to 25.6% greater with the soft-start light-curing mode.
  
  
  CONCLUSIONS
  The polymerization technique using a very low initial intensity (150 mW/cm2/10 s) decreased the microleakage of composite resin restorations.
  
  
  CONCLUSIONS
  A soft-start light-curing approach to resin composite polymerization resulted in less microleakage at enamel and dentin margins in Class V cavities compared with resin composite restorations polymerized using a conventional light-curing approach.
authors.affiliation: Potiguar School of Dentistry, Potiguar University--UnP, RN, Brazil. alexjss@yahoo.com
authors.forename: Alex José Souza
authors.initials: AJ
authors.lastname: Santos
authors.forename: Milena Tais
authors.initials: MT
authors.lastname: Lisso
authors.forename: Flávio Henrique Baggio
authors.initials: FH
authors.lastname: Aguiar
authors.forename: Fabiana Mantovani Gomes
authors.initials: FM
authors.lastname: França
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Lovadino
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D003737:Dental Cavity Preparation; D003763:Dental Leakage / Q000517:prevention & control*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D008027:Light; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects; D018709:Statistics, Nonparametric; D013674:Technology, Dental / Q000379:methods*
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate