title: The contribution of chemical bonding to the short- and long-term enamel bond strengths.
abstract: OBJECTIVE
  MDP (10-methacryloyloxydecyl dihydrogenphosphate) has been proven to possess chemical bonding ability to tooth hard tissues, but its contribution to the enamel bond strength has not been recognized. The aim of this study was to investigate the contribution of chemical bonding to the short- and long-term bovine enamel micro-tensile bond strengths (μTBS).
  
  
  METHODS
  The acid-etched enamel surfaces were treated without any primer (control) or with one of three MDP-containing primers (containing different ratio of MDP/HEMA/Bis-GMA, Kuraray Co.) for 5s, water-sprayed and air-dried. Subsequently, the pretreated enamel surfaces were applied with an etch-and-rinse adhesive Durafill Bond (Heraeus Kulzer) and placed with composite resin Durafill VS (Heraeus Kulzer). The specimens were prepared for μTBS tests after 24-h or 1-yr water storage. The etched enamel surfaces treated with or without MDP-containing primers were analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).
  
  
  RESULTS
  The acid-etched enamel treated with the MDP-primers for a very short time could produce the greater enamel μTBS than the control did (p<0.05), and change enamel micromorphology. No significant different μTBS were found between 24-h and 1-yr water storage (p>0.05). The chemical bonding of MDP on the enamel surfaces was re-confirmed by XPS.
  
  
  CONCLUSIONS
  The additional chemical bonding of MDP around the enamel crystallites of the etched enamel substrate could significantly increase the short- and long-term enamel μTBS, and their μTBS surpass those of the etch-and-rinse adhesive alone.
authors.affiliation: Hospital of Stomatology Affiliated to Zhejiang University School of Medicine, Zhejiang University School of Stomatology, Yan'an Road 395, Hangzhou 310006, China.
authors.forename: Zhenliang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Xiaomiao
authors.initials: X
authors.lastname: Wang
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.forename: Bing
authors.initials: B
authors.lastname: Liang
authors.forename: Tian
authors.initials: T
authors.lastname: Tang
authors.forename: Baiping
authors.initials: B
authors.lastname: Fu
authors.forename: Matthias
authors.initials: M
authors.lastname: Hannig
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D017886:Durapatite; D008689:Methacrylates; D011897:Random Allocation; D019279:Resin Cements; D013718:Tensile Strength; D013997:Time Factors; D014867:Water
chemical_list: D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C470435:durafill bond; D014867:Water; C069749:methacryloyloxydecyl dihydrogen phosphate; D017886:Durapatite