title: Effectiveness and stability of silane coupling agent incorporated in 'universal' adhesives.
abstract: For bonding indirect restorations, some 'universal' adhesives incorporate a silane coupling agent to chemically bond to glass-rich ceramics so that a separate ceramic primer is claimed to be no longer needed. With this work, we investigated the effectiveness/stability of the silane coupling function of the silanecontaining experimentally prepared adhesives and Scotchbond Universal (3MESPE).
  
  
  
  Experimental adhesives consisted of Scotchbond Universal and the silane-free Clearfil S3 ND Quick (Kuraray Noritake) mixed with Clearfil Porcelain Bond Activator (Kuraray Noritake) and the two adhesives to which γ-methacryloxypropyltrimethoxysilane (γ-MPTS) was added. Shear bond strength was measured onto silica-glass plates; the adhesive formulations were analyzed using fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (NMR). In addition, shear bond strength onto CAD-CAM composite blocks was measured without and after thermo-cycling ageing.
  
  
  
  A significantly higher bond strength was recorded when Clearfil Porcelain Bond Activator was freshly mixed with the adhesive. Likewise, the experimental adhesives, to which γ-MPTS was added, revealed a significantly higher bond strength, but only when the adhesive was applied immediately after mixing; delayed application resulted in a significantly lower bond strength. FTIR and (13)C NMR revealed hydrolysis and dehydration condensation to progress with the time after γ-MPTS was mixed with the two adhesives. After thermo-cycling, the bond strength onto CAD-CAM composite blocks remained stable only for the two adhesives with which Clearfil Porcelain Bond Activator was mixed.
  
  
  
  Only the silane coupling effect of freshly prepared silanecontaining adhesives was effective. Clinically, the use of a separate silane primer or silane freshly mixed with the adhesive remains recommended to bond glass-rich ceramics.
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: Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan. Electronic address: a.sonoda@aist.go.jp.
authors.forename: Akinari
authors.initials: A
authors.lastname: Sonoda
authors.affiliation: Department of Occlusion and Removable Prosthodontics, Okayama University Hospital, 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: Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan. Electronic address: y-makita@aist.go.jp.
authors.forename: Yoji
authors.initials: Y
authors.lastname: Makita
authors.affiliation: Division of Applied Chemistry, 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: Department of Biomaterials, Graduate School of Medicine, Dentistry and Phamaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: mirie@md.okayama-u.ac.jp.
authors.forename: Masao
authors.initials: M
authors.lastname: Irie
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: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, 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: D000269:Adhesives; D001840:Dental Bonding; D003776:Dental Porcelain; D008422:Materials Testing; D008689:Methacrylates; D019279:Resin Cements; D012821:Silanes
chemical_list: D000269:Adhesives; D008689:Methacrylates; D019279:Resin Cements; D012821:Silanes; D003776:Dental Porcelain; C017492:methacryloxypropyltrimethoxysilane
keywords: Bond strength; Coupling agent; FTIR; NMR; Silane; Universal adhesive