Accumulation of Enamel Constituents in Streptococcus mutans Plaque during Intraoral Demineralization

Abstract

Studies were carried out with an intraoral demineralizing system in order to determine whethei calcium and inorganic phosphate (PI) accumulate in plaque during active demineralization of enamel. Blocks of bovine enamel were coated with Streptococcus mutans and were carried in palatal appliances worn by human volunteers. Demineralization was determined as changes in the iodide penetrability (delta Ip) of the enamel surfaces. Ca and PI were determined in the extracellular spaces of the synthetic plaque. Delta Ip increased with time after administration of rinses containing 5% (w/v) sucrose, while plaque pH dropped and then returned towards neutrality. Ca increased to 10.9 ± 2.8 mmol/l at 30 min, while Ca²⁺ and Pi rose to 3.0 ± 2.1 and 9.5 ± 3.1 mmol/l, respectively. The Ca:PI ratio was 1.15. Rinses with 10% (w/v) sucrose gave similar results. Concentrations of Ca and Pi were considerably higher than those in saliva. Accumulation of the mineral constituents was shown to be dependent on metabolic activity of the S. mutans plaque, and experiments in which enamel blocks were replaced with blocks made of acrylic plastic gave Ca and PI concentrations of 2.5 ± 0.6 and 6.6 ± 2.4 mmol/l, respectively, demonstrating that most of the Ca and about one-third of the PI were derived from enamel. The data suggested, furthermore, that Ca and PI were partially bound to complex macromolecules, and that part eventually recrystallized as mineral within the plaque.

The Effect of Sucrose Application Frequency and Basal Nutrient Conditions on the Calcium and Phosphate Content of Experimental Dental Plaque

“…All these studies have been carried out with plaque grown on an enamel substratum, so uptake of Ca from enamel into plaque may have been responsible for failure to find low Ca levels after sugar intake. In fact, Cury et al [1997] noted white spots on the enamel which were especially marked after the 8 times frequency application, supporting the suggestion of Kashket and Yaskell [1990] that enamel provides Ca to plaque under these conditions. Our study, where enamel cannot have affected the results, shows clearly that increasing frequency of sugar application causes the development of plaque having progressively less Ca, i.e.…”

“…All whole-plaque studies to date that we are aware of have been carried out using natural plaque from enamel surfaces, or from enamel surfaces in in situ experiments [Cury et al, 1997] where mineral ion movements may be obscured by contributions from enamel [Kashket and Yaskell, 1990]. Furthermore, overnight starved plaque has been shown to be more susceptible to Ca loss than unstarved plaque [Ashley, 1975], 2-day-old plaque more susceptible than mature plaque [Ashley and Wilson, 1977a], and plaque on free smooth surfaces more susceptible than plaque on the less accessible approximal surfaces of teeth [Wilson and Ashley, 1990].…”

Limitations in the Intraoral Demineralization of Bovine Enamel

“…The present observations did not support the assumption. Instead, the Ca and Pi derived from enamel during active demineralization [Kashket and Yaskell, 1990] appeared to play a significant role in regu lating further mineral dissolution.…”

Effectiveness of Calcium Lactate Added to Food in Reducing Intraoral Demineralization of Enamel

“…With the CL-supplemented sweet cookies, for example, the calcium concentrations in the plaque space rose and then fell from 32.4±6.0mM at 1 min to 13.3±4.1 mM at 15 min ( fig. 2), the latter concentration being no different statisti cally from calcium concentrations in plaque under actively demineralizing conditions [Kashket and Yaskell, 1990]. Calculations using the measured plaque Ca and Pi concen trations [Moreno and Margolis, 1988] indicated that the plaque remained saturated with respect to enamel at 5 min (i.e.…”

“…Presumably, cal cium, would be most effective in regulating demineraliza tion as the plaque pi 1 fell [Kashket and Yaskell, 1990]. Data arc shown in figure 2.…”