title: Relationship between thin-film bond strength as measured by a scratch test, and indentation hardness for bonding agents.
abstract: OBJECTIVE
  To evaluate thin-film bond strength between a bonding agent and human dentin, using a scratch test, and the characteristics and accuracy of measurement.
  
  
  METHODS
  One-step bonding agents (BeautiBond; Bond Force; Adper Easy Bond; Clearfil tri-S Bond) and two-step bonding agents (Cleafil SE Bond; FL-Bond II) were investigated in this study. Flat dentin surfaces were prepared for extracted human molars. The dentin surfaces were ground and bonding agents were applied and light cured. The thin-film bond strength test of the specimens was evaluated by the critical load at which the coated bonding agent failed and dentin appeared. The scratch mark sections were then observed under a scanning electron microscope. Indentation hardness was evaluated by the variation in depth under an applied load of 10gf. Data were compared by one-way ANOVA with the Scheffé's post hoc multiple comparison test (p<0.05). In addition, thin-film bond strength and indentation hardness were analyzed using analysis of correlation and covariance.
  
  
  RESULTS
  The thin-film bond strength of two-step bonding agents were found to be significantly higher than that of one-step bonding agents with small standard deviations. Scratch marks consistently showed adhesive failure in the vicinity of the bonding agent/dentin interface. The indentation hardness showed a trend that two-step bonding agents have greater hardness than one-step bonding agents. A moderately significant correlation (r(2)=0.31) was found between thin-film bond strength and indentation hardness.
  
  
  CONCLUSIONS
  Thin-film bond strength test is a valid and reliable means of evaluating bond strength in the vicinity of the adhesive interface and is more accurate than other methods currently in use. Further, the thin-film bond strength is influenced by the hardness of the cued bonding agent.
authors.affiliation: Division of Oral Functional Science and Rehabilitation, Department of Operative Dentistry, Asahi University School of Dentistry, 1851 Hozumi, Mizuho-city, Gifu 501-0296, Japan; Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, United States. Electronic address: kusakabe@dent.asahi-u.ac.jp.
authors.forename: Shusuke
authors.initials: S
authors.lastname: Kusakabe
authors.affiliation: Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, United States.
authors.forename: H Ralph
authors.initials: HR
authors.lastname: Rawls
authors.affiliation: Division of Oral Functional Science and Rehabilitation, Department of Operative Dentistry, Asahi University School of Dentistry, 1851 Hozumi, Mizuho-city, Gifu 501-0296, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Hotta
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding / Q000379:methods*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008963:Molar; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties
chemical_list: C000612360:Adper Easy One; C000601955:Bond Force dental cement; C438313:Clearfil SE Bond; C515604:Clearfil Tri-S Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C503681:FL-BOND S-1; D019279:Resin Cements; C584662:beautibond; D017438:Bisphenol A-Glycidyl Methacrylate
keywords: Bonding agent; Indentation hardness; Scratch test; Thin-film bond strength