title: Development and testing of novel bisphenol A-free adhesives for lingual fixed retainer bonding.
abstract: To comparatively evaluate the properties of two BPA-free experimental adhesives (EXA, EXB) for lingual fixed retainer bonding versus a commercially available reference material (Transbond LR-TLR) based on BPA-compound.
  
  
  
  The experimental materials were a flowable 60 per cent glass filler-filled UEDMA/TEGDMA flowable composite (EXB) and a 70 per cent glass filler-filled paste composite with PCDMA/UEDMA/TEGDMA co-monomers. The properties tested were degree of conversion (DC%), mechanical properties (Martens hardness-MH, elastic modulus-EIT, elastic index-nIT), effect of prolonged (6 months) water storage (changes in Vickers microhardness-VHN) and pull-out strength employing a multi-stranded wire.
  
  
  
  EXB showed the highest DC% (63.6 per cent), followed by EXA (50.5 per cent) and TRL (44.1 per cent), with all means differences being statistically significant (P < 0.05). The statistical rankings of MH (MPa) and EIT(GPa) means were TLR (76.1MPa; 17.3GPa) > EXA (53MPa; 12.9GPa) > EXB (12.9MPa; 6.7GPa), whereas for nIT,EXB (40 per cent) > EXA (34.9 per cent), TLR (33.6 per cent). All materials were affected by prolonged water storage with significant differences among them in VHN. TLR was the most affected material (ΔVHN = -11 per cent), followed by EXA (ΔVHN = -6.8 per cent) and EXB (ΔVHN = -4.2 per cent). No statistically significant differences were found in the pull-out strength testing (24-24.2 N range) and failure mode (70-77 per cent mixed).
  
  
  
  Considering the differences between the two experimental materials, it may be concluded that the material containing the PCDMA/UEDMA/TEGDMA co-monomers may be used as an alternative to the control.
authors.affiliation: *Department of Orthodontics, School of Dentistry, University of Athens, Greece.
authors.forename: Anna
authors.initials: A
authors.lastname: Iliadi
authors.affiliation: **Clinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Switzerland, theodore.eliades@zzm.uzh.ch.
authors.forename: Theodore
authors.initials: T
authors.lastname: Eliades
authors.affiliation: ***Biomaterials Science Research Group, School of Dentistry, University of Manchester, UK, and.
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.affiliation: ****Department of Biomaterials, School of Dentistry, University of Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Eliades
mesh_terms: D001559:Benzhydryl Compounds / Q000737:chemistry*; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D003188:Composite Resins; D003738:Dental Cements / Q000737:chemistry* / Q000592:standards; D055119:Elastic Modulus / Q000502:physiology*; D005898:Glass / Q000737:chemistry*; D006244:Hardness; D010636:Phenols / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D003738:Dental Cements; D010636:Phenols; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D019279:Resin Cements; C481385:Transbond LR; C111840:flowable hybrid composite; C020946:triethylene glycol dimethacrylate; C006780:bisphenol A; D000098826:Bisphenol A Compounds