title: Adhesive interfacial interaction affected by different carbon-chain monomers.
abstract: OBJECTIVE
  The functional monomer 10-methacryloxydecyl dihydrogen phosphate (10-MDP), recently used in more self-etch adhesives, chemically bonds to hydroxyapatite (HAp) and thus tooth tissue. Although the interfacial interaction of the phosphoric-acid functional group of 10-MDP with HAp-based substrates has well been documented, the effect of the long carbon-chain spacer of 10-MDP on the bonding effectiveness is far from understood.
  
  
  METHODS
  We investigated three phosphoric-acid monomers, 2-methacryloyloxyethyl dihydrogen phosphate (2-MEP), 6-methacryloyloxyhexyl dihydrogen phosphate (6-MHP) and 10-MDP, that only differed for the length of the carbon chain, on their chemical interaction potential with HAp and dentin, this correlatively using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial 6-MHP and 10-MDP containing adhesives were investigated as well.
  
  
  RESULTS
  XRD revealed that on HAp only 10-MDP produced monomer-calcium salts in the form of 'nano-layering', while on dentin all monomers produced 'nano-layering', but with a varying intensity in the order of 10-MDP>6-MHP>2-MEP. TEM confirmed that 10-MDP formed the thickest hybrid and adhesive layer. XRD and TEM revealed 'nano-layering' for all commercial adhesives on dentin, though less intensively for the 6-MHP containing adhesive than for the 10-MDP ones.
  
  
  CONCLUSIONS
  It is concluded that not only the phosphoric-acid group but also the spacer group, and its length, affect the chemical interaction potential with HAp and dentin. In addition, the relatively strong 'etching' effect of 10-MDP forms more stable monomer-Ca salts, or 'nano-layering', than the two shorter carbon-chain monomers tested, thereby explaining, at least in part, the better bond durability documented with 10-MDP containing adhesives.
authors.affiliation: KU Leuven BIOMAT, Department of Oral Health Research, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Belgium.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yoshihara
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nagaoka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hayakawa
authors.forename: Takumi
authors.initials: T
authors.lastname: Okihara
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Maruo
authors.forename: Goro
authors.initials: G
authors.lastname: Nishigawa
authors.forename: Shogo
authors.initials: S
authors.lastname: Minagi
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Osaka
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D002417:Cattle; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D008689:Methacrylates / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry; D010755:Organophosphates / Q000737:chemistry; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: C000595499:2-methacryloyloxyethyl dihydrogen phosphate; C000595500:6-methacryloyloxyhexyl dihydrogen phosphate; D008689:Methacrylates; D010755:Organophosphates; D002244:Carbon; C069749:methacryloyloxydecyl dihydrogen phosphate; D017886:Durapatite; D002118:Calcium
keywords: Adhesive; Dentin; Functional monomer; TEM; X-ray diffraction