In situ studies of pellicle formation on hydroxyapatite discs

The formation of acquired enamel pellicle on hydroxyapatite (HA) discs of known surface area carried in the mouth was studied; discs were carried in the mouth for 30 s, 1, 5, 10 and 20 min. Similar amounts of protein were found on the discs at each time-point, as determined by ninhydrin analyses. The amounts of amylase and lysozyme detected remained stable after 5 min of exposure of the discs to the mouth. Assay of the discs for fructosyl- and glucosyltransferase activities revealed that fructosyltransferase activity increased up to 1 min of exposure to the mouth and decreased when kept in the mouth for longer periods; glucosyltransferase activity, in contrast, increased the longer the discs were kept in the mouth. This in situ model provides insight into the activities of various enzymes during the first 20 min of pellicle formation. The effects of rinsing with sucrose and sugar alcohols on pellicle formation on the discs were also explored. The discs were placed in the mouth for 30 s, 1, 5, 10 and 20 min, preceded by rinsing with either distilled deionized water, sucrose, sorbitol, xylitol or phosphate-buffered saline. Western blot analyses of disc eluates with antiserum/antibody preparations to various salivary components revealed distinct patterns of deposition of bacterial and salivary components depending on the composition of the rinse. These studies confirm that salivary molecules and bacteria are deposited on apatitic surfaces in a selective manner and reveal that pellicle formation may be influenced by composition of diet. It is apparent that this in situ model could be used in screening potential antiplaque agents.