title: On the stiffness of demineralized dentin matrices.
abstract: Resin bonding to dentin requires the use of self-etching primers or acid etching to decalcify the surface and expose a layer of collagen fibrils of the dentin matrix. Acid-etching reduces the stiffness of demineralized dentin from approximately 19 GPa-1 MPa, requiring that it floats in water to prevent it from collapsing during bonding procedures. Several publications show that crosslinking agents like gluteraladehyde, carbodiimide or grape seed extract can stiffen collagen and improve resin-dentin bond strength.
  
  
  OBJECTIVE
  The objective was to assess a new approach for evaluating the changes in stiffness of decalcified dentin by polar solvents and a collagen cross-linker.
  
  
  METHODS
  Fully demineralized dentin beams and sections of etched coronal dentin were subjected to indentation loading using a cylindrical flat indenter in water, and after treatment with ethanol or ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). The stiffness was measured as a function of strain and as a function of loading rate from 1 to 50 μm/s.
  
  
  RESULTS
  At a strain of 0.25% the elastic modulus of the fully demineralized dentin was approximately 0.20 MPa. It increased to over 0.90 MPa at strains of 1%. Exposure to ethanol caused an increase in elastic modulus of up to four times. Increasing the loading rate from 1 to 50 μm/s caused an increase in the apparent modulus of up to three times in both water and ethanol. EDC treatment caused increases in the stiffness in fully demineralized samples and in acid-etched demineralized dentin surfaces in situ.
  
  
  CONCLUSIONS
  Changes in the mechanical behavior of demineralized collagen matrices can be measured effectively under hydration via indentation with cylindrical flat indenters. This approach can be used for quantifying the effects of bonding treatments on the properties of decalcified dentin after acid etching, as well as to follow the loss of stiffness over time due to enzymatic degradation.
authors.affiliation: Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA.
authors.forename: Heonjune
authors.initials: H
authors.lastname: Ryou
authors.affiliation: Department of Biomedicine, Unit of Dental Sciences and Biomaterials, University of Trieste, Trieste, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Turco
authors.affiliation: Department of Biomedicine, Unit of Dental Sciences and Biomaterials, University of Trieste, Trieste, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Breschi
authors.affiliation: Department of Oral Biology, College of Dental Medicine, Georgia Health Sciences University, Augusta, GA, USA; Department of Endodontics, College of Dental Medicine, Georgia Health Sciences University, Augusta, GA, USA.
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.affiliation: Department of Oral Biology, College of Dental Medicine, Georgia Health Sciences University, Augusta, GA, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.affiliation: Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA; Department of Restorative Dentistry and Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA, USA. Electronic address: darola@uw.edu.
authors.forename: Dwayne
authors.initials: D
authors.lastname: Arola
mesh_terms: D000134:Acid Etching, Dental; D000293:Adolescent; D002234:Carbodiimides / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D003804:Dentin / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D055119:Elastic Modulus; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D013499:Surface Properties; D013718:Tensile Strength; D055815:Young Adult
chemical_list: C518491:1-ethyl-3-(3-(diethylamino)propyl)carbodiimide; D002234:Carbodiimides; D003432:Cross-Linking Reagents; C093073:Demineralized Dentin Matrix; D017220:Dentin-Bonding Agents; D000431:Ethanol
keywords: Collagen; Crosslinking; Dentin bonding agents; Durability; EDC; Endogenous proteinases; Stiffness