title: Influence of resin composite polymerization techniques on microleakage and microhardness.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the marginal microleakage and the extent of polymerization in Class II resin composite restorations prepared with two restorative techniques and two polymerization systems. METHOD AND MATERIALS One hundred twenty Class II cavities were prepared in bovine teeth and randomly divided into four groups: Bulk placement and conventional polymerization (Conv 1); buccolingual increments and conventional polymerization (Conv 3); bulk placement and soft-start polymerization (Soft 1); buccolingual increments and soft-start polymerization (Soft 3). All cavities were restored with the Z100/Single Bond system. After thermocycling, the specimens were immersed in 2% methylene blue solution and then evaluated for microleakage. Half of the samples were embedded in polyester resin and polished. The Knoop microhardness of the restorations was measured.
  
  
  RESULTS
  There was no dye penetration in 54.44% of Conv 1, 70.11% of Conv 3, 42.53% of Soft 1, and 63.22% of Soft 3 specimens. There were statistically significant differences in microleakage among groups. There were no statistically significant differences in microhardness among any groups at any depth.
  
  
  CONCLUSIONS
  The incremental placement technique resulted in less microleakage. The soft-start system provided adequate polymerization but could not improve marginal sealing.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry of Piracicaba, University of Campinas, Piracicaba, São Paulo, Brazil.
authors.forename: Cristiane Mariote
authors.initials: CM
authors.lastname: Amaral
authors.forename: Ana Karina Barbieri Bedran
authors.initials: AK
authors.lastname: de Castro
authors.forename: Luiz André Freire
authors.initials: LA
authors.lastname: Pimenta
authors.forename: Glaucia Maria Boni
authors.initials: GM
authors.lastname: Ambrosano
mesh_terms: D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003763:Dental Leakage / Q000517:prevention & control*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D017220:Dentin-Bonding Agents; D006244:Hardness; D008027:Light; D008422:Materials Testing; D015588:Observer Variation; D011108:Polymers / Q000737:chemistry; D011897:Random Allocation; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects*; D013674:Technology, Dental; D015040:Zirconium / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D011108:Polymers; C083568:Z100 composite resin; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium