title: Quantification of monomer elution and carbon-carbon double bonds in dental adhesive systems using HPLC and micro-Raman spectroscopy.
abstract: OBJECTIVE
  To quantify monomer elution from different adhesive systems using reverse-phase high-performance liquid chromatography (HPLC) and correlate this elution with the ratio of carbon-carbon double bonds from monomer to polymer (RDB) obtained using micro-Raman spectroscopy.
  
  
  METHODS
  Thirty dentine discs were cut from 30 human, intact, third molars and randomly allocated to five groups according to the adhesive applied: total-etch, Excite (Ivoclar Vivadent), two-bottle self-etch, Clearfil SE (Kuraray), one-bottle self-etch, Clearfil 3S (Kuraray), ormocer-based, Admira (Voco) and Filtek Silorane adhesive system (FS) (3M ESPE). Monomer elution was studied 1h, 6h, 24h, 96h and 7 days after immersion in 75% ethanol/water. The RDB was calculated immediately after light-curing and thereafter at 24h and 7 days. The data were statistically analysed using one-way ANOVA and Pearson's correlation coefficient (p<0.05).
  
  
  RESULTS
  More than 90% of the whole elution occurred during the first 1h, except for BisGMA in FS, with the highest absolute amount from Clearfil SE and the highest wt% from Admira. Initial RDB was in the ascending order FS<Admira<Excite<Clearfil SE<Clearfil 3S. In all groups, the RDB was significantly higher after 24h and 7 days than immediately after light-curing (p<0.05). Negative correlation was found only for the elution of HEMA and the RDB of Clearfil 3S.
  
  
  CONCLUSIONS
  Different adhesive systems showed different monomer elution kinetics. In all systems, the RDB increased after monomer elution. Overall, no direct correlation exists between the RDB of adhesives and the elution of unreacted monomers.
authors.affiliation: Edinburgh Postgraduate Dental Institute, The University of Edinburgh, Lauriston Building (4th floor), Lauriston Place, Edinburgh EH3 9HA, United Kingdom. vesna.miletic@gmail.com
authors.forename: Vesna
authors.initials: V
authors.lastname: Miletic
authors.forename: Ario
authors.initials: A
authors.lastname: Santini
authors.forename: Ivan
authors.initials: I
authors.lastname: Trkulja
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates / Q000032:analysis; D015394:Molecular Structure; D044367:Phase Transition; D019279:Resin Cements / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
chemical_list: D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements