title: Soft-start polymerization and marginal gap formation in vitro.
abstract: OBJECTIVE
  To determine the effect of soft-start polymerization of resin-based composites on the marginal gap formation in dentin cavities.
  
  
  METHODS
  Cylindrical cavities were prepared in dentin in extracted human molars. The cavities were distributed into 8 groups. The teeth in groups 1-4 were treated with Scotchbond Multi-Purpose and restored with Z100, and the teeth in groups 5-8 were treated with OptiBond FL and restored with Herculite XRV. The restorations were light-cured for 40 s by four different curing modes. The marginal gap formation was measured in a light microscope after a 20 min water-storage, and the wall-to-wall contraction was calculated as the widest gap in percent of the cavity diameter.
  
  
  RESULTS
  Soft-start light curing did not influence wall-to-wall contraction in dentin cavities. OptiBond FL and Herculite XRV showed less wall-to-wall contraction than did Scotchbond Multi-Purpose and Z100.
  
  
  CONCLUSIONS
  The soft-start polymerization procedures studied did not improve the marginal adaptation of two resin composites bonded to dentin cavities compared with conventional polymerization.
authors.affiliation: Department of Dental Materials, School of Dentistry, University of Copenhagen, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Sahafi
authors.forename: A
authors.initials: A
authors.lastname: Peutzfeldt
authors.forename: E
authors.initials: E
authors.lastname: Asmussen
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003737:Dental Cavity Preparation / Q000145:classification; D018772:Dental Marginal Adaptation; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D008027:Light; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects; D012822:Silicon Dioxide; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013997:Time Factors; D014783:Viscosity; D014867:Water; D015040:Zirconium
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C092987:Optibond; D011108:Polymers; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C083568:Z100 composite resin; D014867:Water; C065770:Herculite XR; D012822:Silicon Dioxide; D015040:Zirconium