title: Chemical analysis and bonding reaction of RelyX Unicem and Bifix composites--a comparative study.
abstract: OBJECTIVE
  The chemical and physical properties of the dual curing luting composites RelyX Unicem (3M ESPE) and Bifix (VOCO) were analyzed with regard to their elemental composition, surface morphology and polymerization reaction. The bonding of both materials to hydroxyapatite (HAp) was studied.
  
  
  METHODS
  The main components were analyzed by XPS and EDX. The minor components were identified with ICP-OES. Moreover, the morphology was examined by SEM and the polymerization reaction products were investigated using GPC. XPS was also applied to study the bonding mechanisms to HAp.
  
  
  RESULTS
  The inorganic product particles consist of an Al-Si-Na-glass network, which incorporates radiopaque strontium and barium for Bifix and strontium and lanthanum for RelyX Unicem. RelyX Unicem contains about 10% fluoride and 2% Ca(OH)(2), whereas Bifix comprises 2% fluoride. After polymerization, reaction products of 10(5)-10(6)g/mol were identified with RelyX Unicem. Both products contain mono- and oligomeric compounds. The reaction with HAp generates calcium atoms with a reduced binding energy. They act as an electron acceptor and show chemical interaction between the composite and HAp. With RelyX Unicem 86% of the calcium atoms reacted, compared to 65% with Bifix.
  
  
  CONCLUSIONS
  The intense chemical interaction of RelyX Unicem with HAp seems to be relevant to clinical aspects and explains the mechanical product properties. After setting, a polymer was found with RelyX Unicem but only monomeric/oligomeric products were identified at the surface of Bifix.
authors.affiliation: Institute of Physical Chemistry, University of Münster, Germany.
authors.forename: Hans U V
authors.initials: HU
authors.lastname: Gerth
authors.forename: Till
authors.initials: T
authors.lastname: Dammaschke
authors.forename: Harald
authors.initials: H
authors.lastname: Züchner
authors.forename: Edgar
authors.initials: E
authors.lastname: Schäfer
mesh_terms: D000538:Aluminum Silicates / Q000032:analysis; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003799:Dental Stress Analysis; D017886:Durapatite / Q000737:chemistry*; D005459:Fluorides / Q000032:analysis; D006860:Hydrogen Bonding; D007284:Inlays; D008422:Materials Testing; D008670:Metals / Q000032:analysis; D008689:Methacrylates / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D044367:Phase Transition; D010710:Phosphates / Q000032:analysis; D019279:Resin Cements / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013431:Sulfates / Q000032:analysis; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; C515607:Bifix composite; D003188:Composite Resins; D008670:Metals; D008689:Methacrylates; D010710:Phosphates; C483701:Rely X Unicem; D019279:Resin Cements; D013431:Sulfates; D017886:Durapatite; D005459:Fluorides