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

UNLABELLED: Plaque mineralisation is a multi-factorial process involving plaque pH, nucleation, inhibitors and promotors. It is poorly understood because of its complexity. OBJECTIVE: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.