title: Effects of polyphosphates and fluoride on hydroxyapatite dissolution: A pH-stat investigation.
abstract: OBJECTIVE
  This study investigated the immediate and sustained effect of sodium trimetaphosphate (TMP) and sodium hexametaphosphate (HMP) associated or not with fluoride (F) on hydroxyapatite (HA) dissolution using an erosion-like model, considering as well as the influence of salivary coating.
  
  
  METHODS
  Baseline dissolution rates were determined for HA discs using a pH-stat system. In the first set of experiments, HA discs were treated with 1100μgF/mL, 1% or 8% of HMP, 1% or 8% of TMP and 1100μgF/mL associated with 1% or 8% of HMP or TMP, totaling 9 groups (n=8). In a second phase, HA discs were kept in pooled human saliva at 37°C for 2h before treatment with deionised water and 1100μgF/mL associated with 1% or 8% of HMP or TMP, totaling 5 groups (n=8). The post-treatment dissolution rate was determined from three consecutive 30-min assays. Data were analysed using 2 and 3-way ANOVA followed by Fisher and Holm-Sidak methods, respectively (α=0.05).
  
  
  RESULTS
  All test solutions promoted reduction in HA dissolution rate when compared to baseline control in the first post-treatment run (p<0.001). However, a synergistic effect was only observed between fluoride and 1% HMP. Moreover, the duration of inhibitory effect was greater when 8% HMP and 1 or 8% HMP associated with F were assessed (p<0.001). The presence of salivary coating led to higher protection for all groups when compared to discs without coating (p<0.001).
  
  
  CONCLUSIONS
  The reduction of HA dissolution rate, as well as the duration of this effect were influenced by fluoride, type and concentration of phosphate salt and the presence of a salivary coating.
authors.affiliation: Department of Pediatric Dentistry and Public Health, Araçatuba Dental School, Univ. Estadual Paulista (UNESP), Araçatuba, SP, Brazil.
authors.forename: Jackeline Gallo
authors.initials: JG
authors.lastname: do Amaral
authors.affiliation: Department of Pediatric Dentistry and Public Health, Araçatuba Dental School, Univ. Estadual Paulista (UNESP), Araçatuba, SP, Brazil. Electronic address: adelbem@foa.unesp.br.
authors.forename: Alberto Carlos Botazzo
authors.initials: ACB
authors.lastname: Delbem
authors.affiliation: Department of Pediatric Dentistry and Public Health, Araçatuba Dental School, Univ. Estadual Paulista (UNESP), Araçatuba, SP, Brazil.
authors.forename: Juliano Pelim
authors.initials: JP
authors.lastname: Pessan
authors.affiliation: Department of Pediatric Dentistry and Public Health, Araçatuba Dental School, Univ. Estadual Paulista (UNESP), Araçatuba, SP, Brazil.
authors.forename: Michele Mauricio
authors.initials: MM
authors.lastname: Manarelli
authors.affiliation: School of Oral and Dental Sciences, University of Bristol, Bristol, UK.
authors.forename: Michele E
authors.initials: ME
authors.lastname: Barbour
mesh_terms: D017886:Durapatite / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D010710:Phosphates / Q000737:chemistry; D011122:Polyphosphates / Q000737:chemistry*; D012463:Saliva / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013499:Surface Properties; D014077:Tooth Erosion / Q000517:prevention & control
chemical_list: D010710:Phosphates; D011122:Polyphosphates; D012996:Solutions; C012980:fluorophosphate; D017886:Durapatite; C009293:trimetaphosphoric acid; C009285:sodium polymetaphosphate; D005459:Fluorides
keywords: Erosion; Fluoride; Hydroxyapatite; Polyphosphates; Salivary coating