title: Microhardness of dual-polymerizing resin cements and foundation composite resins for luting fiber-reinforced posts.
abstract: BACKGROUND
  The optimal luting material for fiber-reinforced posts to ensure the longevity of foundation restorations remains undetermined.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the suitability of 3 dual-polymerizing resin cements and 2 dual-polymerizing foundation composite resins for luting fiber-reinforced posts by assessing their Knoop hardness number.
  
  
  METHODS
  Five specimens of dual-polymerizing resin cements (SA Cement Automix, G-Cem LincAce, and Panavia F2.0) and 5 specimens of dual-polymerizing foundation composite resins (Clearfil DC Core Plus and Unifil Core EM) were polymerized from the top by irradiation for 40 seconds. Knoop hardness numbers were measured at depths of 0.5, 2.0, 4.0, 6.0, 8.0, and 10.0 mm at 0.5 hours and 7 days after irradiation. Data were statistically analyzed by repeated measures ANOVA, 1-way ANOVA, and the Tukey compromise post hoc test (α=.05).
  
  
  RESULTS
  At both times after irradiation, the 5 resins materials showed the highest Knoop hardness numbers at the 0.5-mm depth. At 7 days after irradiation, the Knoop hardness numbers of the resin materials did not differ significantly between the 8.0-mm and 10.0-mm depths (P>.05). For all materials, the Knoop hardness numbers at 7 days after irradiation were significantly higher than those at 0.5 hours after irradiation at all depths (P<.05). At 7 days after irradiation, the Knoop hardness numbers of the 5 resin materials were found to decrease in the following order: DC Core Plus, Unifil Core EM, Panavia F2.0, SA Cement Automix, and G-Cem LincAce (P<.05).
  
  
  CONCLUSIONS
  The Knoop hardness number depends on the depth of the cavity, the length of time after irradiation, and the material brand. Although the Knoop hardness numbers of the 2 dual-polymerizing foundation composite resins were higher than those of the 3 dual-polymerizing resin cements, notable differences were seen among the 5 materials at all depths and at both times after irradiation.
authors.affiliation: Assistant Professor, Clinic of Fixed Prosthodontics, Nagasaki University Hospital, Nagasaki, Japan. Electronic address: keiichi@nagasaki-u.ac.jp.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Assistant Professor, Department of Prosthodontics, The Stomatological Hospital Affiliated Medical School, Nanjing University, Nanjing, Japan.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Meng
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002484:Cementation / Q000379:methods*; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D005898:Glass / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation*; D019279:Resin Cements / Q000737:chemistry*; D055116:Self-Curing of Dental Resins / Q000379:methods*; D012821:Silanes / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
chemical_list: C469237:Clearfil Core; D003188:Composite Resins; D003764:Dental Materials; C528107:G-Cem resin cement; C438843:Panavia-Fluoro; D011109:Polymethacrylic Acids; D019279:Resin Cements; D012821:Silanes; C500741:Unifil Core; C009753:fiberglass; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate