Plaque as a Reservoir for Active Ingredients

Abstract

The roles of plaque and saliva in the initiation and progression of dental caries are summarised schematically in figure 1. A central feature is the generation of organic acids, such as lactic acid, by acidogenic plaque bacteria following the dietary intake of carbohydrates such as sucrose. As discussed in Chapter 1, saliva performs two direct functions in order to combat enamel dissolution by these acids: (a) the continuous flow of saliva acts to clear the acids from the mouth and (b) the supply of a number of diverse salivary constituents that have 'anticaries activity'. The latter constituents can act on the acids themselves, via buffering or neutralisation, on the bacteria, via inhibition of the metabolic processes involved in acid production, and on the enamel, by maintaining chemical supersaturation in the adjacent plaque fluid. A key indirect function of saliva is as a medium for the transfer of potentially active therapeutic agents, such as fluoride (F), to the site of action.The physical presence of plaque mediates all the above salivary functions through its influence on ionic and molecular transport, whilst plaque components also provide binding sites for many salivary constituents and therapeutic agents. This plaque 'reservoir' function is the theme of this chapter.First, we describe the chemical composition of plaque fluid in relation to caries, then the role of plaque structure. Next, we discuss the influence of F retained in plaque, including site-to-site differences, followed by the effect of treatments that seek to deposit plaque calcium (Ca) and/or inorganic phosphate (Pi). A combination of small sample volumes and low constituent concentrations typically leads to high measurement variability that results, in turn, with authors often having difficulty in discriminating between subject groups.

Biofilm Layers Affect the Treatment Outcomes of NaF and Nano-hydroxyapatite

“…On one hand, a biofilm might retain calcium and phosphate and promote remineralization; on the other hand, a biofilm might be a diffusion barrier for these ions and thus inhibit the efficacy of caries preventive agents. Ample evidence suggests that substantial amounts of calcium can be retained in biofilms through binding to the carboxyl and phosphate groups on the cell wall peptidoglycan of Gram-positive bacteria (Rose et al 1996;Duckworth and Gao 2006). Furthermore, fluoride can accumulate in biofilms through the formation of "calcium fluoride-like" mineral deposits (Lynch and Smith 2012).…”

Pharmacokinetics in the Oral Cavity: Fluoride and Other Active Ingredients

“…Researchers have sought to do this via Ca ion rinses before brushing with f luoridated toothpaste [for review see 36], or by use of a (preferably sub-micron-sized) particulate source of calcium, e.g. nano calcium carbonate [62], calcium fluoride [63], casein phosphopeptide -amorphous calcium phosphate complex [64]. Soluble calcium offers rapid oral delivery and effective retention at all reservoir sites, whilst particulate calcium offers potentially more achievable product stability and controlled slow release in vivo.…”

Topical Fluoride for Preventing Dental Caries in Children and Adolescents

“…Several in vitro investigations suggested that the cariostatic action of fluoride may include an inhibitory effect on the cariogenic organisms [43]. Fluoride may affect bacterial metabolism by a direct inhibition of essential cellular enzymes (directly or in combination by metals), including heme-containing enzymes or other metalloenzymes, and regulatory phosphatases [44].…”

“…The clinical impact of such in vitro findings is today not fully understood [43,44]. Significant antibacterial effects in vivo have been demonstrated only when high concentration of fluoride when used (e.g.…”

“…The precipitation of CaF 2 in early caries lesion and the subsequent release of fluoride under low pH represent a key mechanism for the caries-inhibiting action of topical fluorides. Oral mucosa has also been reported as an important fluoride reservoir, due to its large surface area [43]. However, fluoride retained in dental plaque is more relevant from a clinical perspective, because it can be released under acidic conditions, just when it is most needed to exert its cariostatic action [51].…”