In vitro evaluation of an acidulated phosphate fluoride prophylaxis paste

Abstract

Acidulated phosphate sodium fluoride, acidulated phosphate silicofluoride and stannous fluoride solutions were tested for fluoride and pH compatibility with a number of abrasives. Silicon dioxide was found to be compatible when used with the acidulated phosphate silicofluoride solution. This system was evaluated for enamel fluoride uptake employing various pastes and methods of application. Uptake was determined by treating blocks of intact enamel for 4 min, soaking them for 24 hr in a metastable calcium phosphate solution and finally removing four thin layers for F analysis. It was found that a SiO 2 paste containing 1.2 per cent F from ammonium silicofluoride, 0.1 M phosphate, and having a pH of 3.0 resulted in greater uptake than an acidulated phosphate sodium fluoride topical solution. Fluoride uptake from the paste was not effected by incorporation of 30 per cent glycerol or 2 per cent hydroxethyl cellulose (HEC) into the liquid phase. Reduced or no enamel F uptake occurred from pastes containing 40 per cent sorbitol or combinations of HEC and glycerol or sorbitol. Effectiveness was also reduced by use of quantities of abrasive greater than 50 g per 20 ml F solution. A thicker paste consistency appeared to be a major factor in the reduced uptake. Abrading teeth removed a thin layer of enamel. The resulting loss of fluoride was far more than compensated by allowing the paste to remain on the enamel for an additional time. Thirty second applications of F solutions or pastes were ineffective.