Release of mineral ions in dental plaque following acid production

The release of appreciable amounts of calcium, phosphate and fluoride found in whole plaque into the plaque-fluid phase, following bacterial acid prod uction, can potentially reduce the driving force for tooth demineralization . However, limited information is available on this topic, particularly on the release of fluoride. This study sought to determine the change in calci um, phosphate and fluoride concentrations In plaque fluid after sucrose exp osure. 48 h overnight-fasted supragingival plaque samples were collected fr om all tooth surfaces (with the exception of the lower lingual anterior tee th) of one half of an individual mouth, following a 1 min water rinse. Plaq ue samples were then collected from the other half of the same mouth, follo wing a 292 mM sucrose rinse. Plaque fluid was isolated by centrifugation an d analysed for total calcium and phosphate (ion chromatography) and for fre e fluoride (ion-specific electrode). Samples were collected from seven indi viduals. Following sucrose exposure, plaque-fluid pH decreased significantl y from 6.5 +/- 0.3 to 5.4 +/- 0.2; calcium concentrations (mmol/l) also inc reased significantly (p < 0.01) from 1.9 +/- 0.5 to 5.0 +/- 2.1. Fluoride a nd phosphate concentrations in plaque fluid, however, did not increase sign ificantly after sucrose exposure: mean concentrations (mmol/l) of fluoride after the water and sucrose rinses were 0.006 +/- 0.003 and 0.005 +/- 0.002 , respectively, and mean phosphate concentrations (mmol/l) were 11.0 +/- 2. 0 and 12.0 +/- 3.0, respectively. When results were expressed per wet plaqu e weight, phosphate concentrations were also found to increase significantl y. The same trends were observed when additional plaque samples were treate d in vitro with sucrose: fluoride-ion activity did not increase in plaque u nder in vivo-like conditions. (C) 1999 Elsevier Science Ltd. All rights res erved.