The influence of saliva on the dissolution of calcium fluoride after application of different fluoride gels in vitro.
OBJECTIVE
To determine the formation and dissolution of calcium fluoride on the enamel surface after application of two fluoride gel-saliva mixtures.


METHODS
From each of 80 bovine incisors, two enamel specimens were prepared and subjected to two different treatment procedures. In group 1, 80 specimens were treated with a mixture of an amine fluoride gel (1.25% F-; pH 5.2; 5 minutes) and human saliva. In group 2, 80 enamel blocks were subjected to a mixture of sodium fluoride gel (1.25% F; pH 5.5; 5 minutes) and human saliva. Subsequent to fluoride treatment, 40 specimens from each group were stored in human saliva and sterile water, respectively. Ten specimens were removed after each of 1 hour, 24 hours, 2 days, and 5 days and analyzed according to potassium hydroxide-soluble fluoride.


RESULTS
Application of amine fluoride gel resulted in a higher amount of potassium hydroxide-soluble fluoride than did sodium fluoride gel 1 hour after application. Saliva exerted an inhibitory effect according to the dissolution rate of calcium fluoride. However, after 5 days, more than 90% of the precipitated calcium fluoride was dissolved in the amine fluoride group, and almost all potassium hydroxide-soluble fluoride was lost in the sodium fluoride group. Calcium fluoride apparently dissolves rapidly, even at almost neutral pH.


CONCLUSIONS
Considering the limitations of an in vitro study, it is concluded that highly concentrated fluoride gels should be applied at an adequate frequency to reestablish a calcium fluoride-like layer.
Hellwig
Elmar
E
Department of Operative Dentistry and Periodontology, University Clinic of Dentistry, Albert-Ludwigs-University Freiburg, Freiburg, Germany. Elmar.Hellwig@uniklinik-freiburg.de
Polydorou
Olga
O
Lussi
Adrian
A
Kielbassa
Andrej M
AM
Altenburger
Markus J
MJ
D000818:Animals; D002124:Calcium Fluoride / Q000493:pharmacokinetics*; D002327:Cariostatic Agents / Q000008:administration & dosage* / Q000032:analysis; D002417:Cattle; D011232:Chemical Precipitation; D003743:Dental Enamel / Q000187:drug effects / Q000378:metabolism*; D003959:Diamines / Q000008:administration & dosage; D005459:Fluorides / Q000008:administration & dosage* / Q000032:analysis; D005782:Gels; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D012463:Saliva / Q000378:metabolism*; D012969:Sodium Fluoride / Q000008:administration & dosage; D012995:Solubility; D013997:Time Factors; D014867:Water / Q000737:chemistry
D002327:Cariostatic Agents; D003959:Diamines; D005782:Gels; D006878:Hydroxides; D017680:Potassium Compounds; D014867:Water; C495399:Olaflur; D012969:Sodium Fluoride; D002124:Calcium Fluoride; D005459:Fluorides; C029943:potassium hydroxide