Human dental plaque microcosm biofilms: effect of nutrient variation on calcium phosphate deposition and growth

Plaque mineralisation is a multi-factorial process involving plaque pH, nucleation, inhibitors and promotors. It is poorly understood because of its complexity.

To establish the effects of amino acids and peptones in the simulated oral fluid BMM, a saliva analogue DMM and modifications of these on mineral deposition into dental plaque biofilm microcosms.

Microcosms were cultured for up to 35 days in an Artificial Mouth pulsed with sucrose, followed by 10 days periodic treatment with a pH 5.0 calcium-phosphate-monofluorophosphate-urea solution (CPMU).

Initial biofilm doubling times were 3-7h, which then slowed and varied under the different nutrient conditions although their pH behaviour was similar. In BMM, mineral deposition was 20% that of DMM, but removal of BMM peptones increased deposition 12-fold. Substitution of the amino acids in DMM by casein did not affect deposition levels, but their removal leaving mucin the sole macronutrient, increased mineral deposition three-fold, reaching 40 mmol Ca/g protein.

These substantial increases in mineral deposition when the macronutrient concentration is reduced indicates probable changes in the nucleating, inhibitory and Ca-binding properties of the simulated oral fluids themselves and/or changes in the plaque microbiota and their crystal nucleators and inhibitors.