The release of appreciable amounts of
calcium, phosphate and
fluoride found in whole plaque into the plaque-fluid phase, following bacterial
acid production, 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
calcium, phosphate and
fluoride concentrations in plaque fluid after
sucrose exposure. 48 h overnight-fasted supragingival plaque samples were collected from all tooth surfaces (with the exception of the lower lingual anterior teeth) of one half of an individual mouth, following a 1 min water rinse. Plaque samples were then collected from the other half of the same mouth, following a 292 mM
sucrose rinse. Plaque fluid was isolated by centrifugation and analysed for total
calcium and
phosphate (ion chromatography) and for free
fluoride (ion-specific
electrode). Samples were collected from seven individuals. Following
sucrose exposure, plaque-fluid pH decreased significantly from 6.5+/- 0.3 to 5.4+/-0.2;
calcium concentrations (mmol/l) also increased significantly (p < 0.01) from 1.9+/-0.5 to 5.0+/-2.1.
Fluoride and
phosphate concentrations in plaque fluid, however, did not increase significantly 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 plaque weight,
phosphate concentrations were also found to increase significantly. The same trends were observed when additional plaque samples were treated in vitro with
sucrose:
fluoride-ion activity did not increase in plaque under in vivo-like conditions.