title: Functional monomer impurity affects adhesive performance.
abstract: OBJECTIVE
  The functional monomer 10-MDP has been considered as one of the best performing functional monomers for dental adhesives. Different adhesives containing 10-MDP are commercially available, among which many so-called 'universal' adhesives. We hypothesize that the quality of the functional monomer 10-MDP in terms of purity may affect bonding performance.
  
  
  METHODS
  We therefore characterized three different 10-MDP versions (10-MDP_KN provided by Kuraray Noritake; 10-MDP_PCM provided by PCM; 10-MDP_DMI provided by DMI) using NMR, and analyzed their ability to form 10-MDP_Ca salts on dentin using XRD. The 'immediate' and 'aged' micro-tensile bond strength (μTBS) to dentin of three experimental 10-MDP primers was measured. The resultant interfacial adhesive-dentin ultra-structure was characterized using TEM.
  
  
  RESULTS
  NMR disclosed impurities and the presence of 10-MDP dimer in 10-MDP_PCM and 10-MDP_DMI. 10-MDP_PCM and 10-MDP_DMI appeared also sensitive to hydrolysis. 10-MDP_KN, on the contrary, contained less impurities and dimer, and did not undergo hydrolysis. XRD revealed more intense 10-MDP_Ca salt deposition on dentin induced by 10-MDP_KN. The adhesive based on the experimental 10-MDP_KN primer resulted in a significantly higher 'immediate' bond strength that remained stable upon aging; the μTBS of the experimental 10-MDP_PCM and 10-MDP_DMI adhesives significantly dropped upon aging. TEM revealed thicker hybridization and more intense nano-layering for 10-MDP_KN.
  
  
  CONCLUSIONS
  It was concluded that primer impurities and the presence of 10-MDP dimer affected not only hybridization, but also reduced the formation of 10-MDP_Ca salts and nano-layering. 10-MDP in a high purity grade is essential to achieve durable bonding.
authors.affiliation: Center for Innovative Clinical Medicine, Okayama University Hospital, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: k-yoshi@md.okayama-u.ac.jp.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yoshihara
authors.affiliation: Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: nagaoka@okayama-u.ac.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nagaoka
authors.affiliation: Division of Chemical and Biological Technology, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan. Electronic address: okihara@cc.okayama-u.ac.jp.
authors.forename: Takumi
authors.initials: T
authors.lastname: Okihara
authors.affiliation: Division of Chemical and Biological Technology, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan. Electronic address: mkurohos@cc.okayama-u.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Kuroboshi
authors.affiliation: Biomaterials Laboratory Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan. Electronic address: satoshi@okayama-u.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hayakawa
authors.affiliation: Department of Occlusion and Removable Prosthodontics, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: ykmar@md.okayama-u.ac.jp.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Maruo
authors.affiliation: Department of Occlusion and Removable Prosthodontics, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: goro@md.okayama-u.ac.jp.
authors.forename: Goro
authors.initials: G
authors.lastname: Nishigawa
authors.affiliation: BIOMAT, Department of Oral Health Research, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7 blok a bus 7001, B-3000 Leuven, Belgium. Electronic address: jan.demunck@med.kuleuven.be.
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.affiliation: Department of Biomaterials and Bioengineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8586, Japan. Electronic address: yasuhiro@den.hokudai.ac.jp.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yoshida
authors.affiliation: BIOMAT, Department of Oral Health Research, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7 blok a bus 7001, B-3000 Leuven, Belgium. Electronic address: bart.vanmeerbeek@med.kuleuven.be.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D000818:Animals; D002417:Cattle; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: C438313:Clearfil SE Bond; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C069749:methacryloyloxydecyl dihydrogen phosphate
keywords: Adhesion; Dentin; Functional monomer; Impurity; NMR; TEM