title: Glass ionomer cement: evidence pointing to fluorine release in the form of monofluorophosphate in addition to fluoride ion.
abstract: The fluoride ion released from glass ionomer cements into water is reportedly, in part, complexed with other elements present in the cement. When measured using ion selective electrode potentiometry (ISE) a decomplexant TISAB IV (T) is used to convert all fluoride to F- ion which the ISE can detect. In this study, an additional decomplexing procedure (H) designed to hydrolyse fluorine covalently bonded to phosphorus in the monofluorophosphate (MFP) ion into F- was also used. The soluble products from three glass ionomers were analysed by both techniques (H & T). Five 1 x 10 mm discs were each immersed in 10 ml of de-ionised water. This was changed and 4 ml analysed by T and 4 ml by H at 1, 2, 3, 6, 10, 13, 17, 21, 24, 28, and 31 days. H was greater than T for 161 of the 165 pairs ( chi2=74.7, p=<0.001 ). The total cumulative F release H (in micromol/g cement) at 31 days for AH2 was 122.3, s.d. 30.8; LG26 44.0, s.d. 1.55; LG30 10.0, s.d. 3.15 as compared T results of 100.1, s.d. 31.1; 30.3, s.d. 1.92; 3.7, s.d. 1.36, respectively. In all three cases the H was significantly greater than T (matched pair 't' test with p=0.01 or less). H-T was show to have a very strong associative relationship with t1/2 (R2=0.98 or greater p<0.001 ). Evaluating the ratio of P:F in the cements in comparison with the ratio of additional F measured by H to that measured by T produced a relationship log[(H-T)/T]=0.28 x log[P/F]-0.45 with R2=0.999. It is concluded that glass ionomers release more fluorine than is detected by ISE using TISAB IV. If this F is in the form of MFP this may be released more completely into saliva than F as F-, release of which is substantially reduced by Ca2+, since calcium monofluorophosphate is more soluble than CaF2.
authors.affiliation: Department of Biomaterials in Relation to Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK. r.w.billington@qmul.ac.uk
authors.forename: R W
authors.initials: RW
authors.lastname: Billington
authors.forename: J A
authors.initials: JA
authors.lastname: Williams
authors.forename: A
authors.initials: A
authors.lastname: Dorban
authors.forename: G J
authors.initials: GJ
authors.lastname: Pearson
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D005459:Fluorides / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000032:analysis* / Q000737:chemistry*; D007477:Ions; D008422:Materials Testing / Q000379:methods*; D010710:Phosphates / Q000737:chemistry*
chemical_list: D005899:Glass Ionomer Cements; D007477:Ions; D010710:Phosphates; C012980:fluorophosphate; D005461:Fluorine; D005459:Fluorides