title: The effects of bonding system and light curing method on reducing stress of different C-factor cavities.
abstract: OBJECTIVE
  The effect of the slow-start curing method on the marginal sealing and cavity wall adaptation on resin composite restorations with different C-factors was evaluated.
  
  
  METHODS
  Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor=2.3) or 2 mm in diameter (C-factor=3) were prepared on flat superficial bovine dentin surfaces. The teeth were restored with Clearfil Photo Bond, Clearfil Liner Bond 2 or Super-Bond D Liner adhesive systems followed by Photo Clearfil Bright composite. The resins were cured with a conventional method using 600 mW/cm2 (tip-to-resin distance 0 mm) for 60 s, or the slow-start curing method of 270 mW/cm2 (tip-to-resin distance 10 mm) for 10 s, followed by a 5-s interval, then 50 s at 600 mW/cm2. After thermocycling, a dye penetration test was carried out. The dye penetration length was calculated as a percentage of the total cavity wall length.
  
  
  RESULTS
  Cavity-wall gap formation increased when the C-factor increased from 2.3 to 3, except in one material, Super-Bond D Liner, which showed good marginal sealing and resin composite adaptation to the cavity wall regardless of light curing method and C-factor.
  
  
  CONCLUSIONS
  It is necessary to take care when a cavity with a high C-factor is to be restored with resin composite. The combination of a flexible adhesive and the slow-start curing method would seem to be effective in reducing polymerization contraction stress for large C-factor cavities.
authors.affiliation: Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Japan. yoshikawa.ope@tmd.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: M F
authors.initials: MF
authors.lastname: Burrow
authors.forename: J
authors.initials: J
authors.lastname: Tagami
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003737:Dental Cavity Preparation / Q000145:classification / Q000379:methods*; D003763:Dental Leakage / Q000145:classification; D018772:Dental Marginal Adaptation; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005456:Fluorescent Dyes; D008027:Light; D008689:Methacrylates / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012235:Rhodamines; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013816:Thermodynamics; D013997:Time Factors
chemical_list: C112274:Clearfil Liner Bond 2; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D005456:Fluorescent Dyes; D008689:Methacrylates; D011108:Polymers; D019279:Resin Cements; D012235:Rhodamines; C084543:Super Bond D-Liner; C074669:Clearfil Photo Bond; C091838:Clearfil Photo Anterior; C022027:lissamine rhodamine B