Calcium and water diffusion in single-species model bacterial plaques

Area of Science:

• Oral Microbiology
• Biophysical Chemistry
• Dental Research

Background:

• Dental plaque is a complex biofilm influencing mineral exchange.
• Understanding diffusion within plaque is crucial for dental caries research.

Purpose of the Study:

• To quantify the diffusion of tritiated water and calcium-45 (45Ca) through single-species model dental plaques.
• To investigate the effects of pH and calcium concentration on diffusion coefficients and permeability.

Main Methods:

• Diffusion measurements were performed using a diaphragm cell technique.
• Apparent diffusion coefficients were determined for tritiated water and 45Ca in plaques of Streptococcus downei, Streptococcus sanguis, and Corynebacterium matruchotii.
• Effective diffusion coefficients for 45Ca were analyzed using lag-time measurements.

Main Results:

• A small but significant decrease in tritiated water diffusion was observed between pH 7.0 and 5.0.
• Calcium diffusion showed a smaller, non-significant decrease at reduced pH, attributed to plaque shrinkage.
• Effective diffusion coefficients for 45Ca were significantly reduced at low carrier concentrations, indicating calcium binding.

Conclusions:

• Plaque permeability to water and calcium is moderately affected by pH.
• Calcium diffusion is concentration-dependent due to binding, with implications for dental caries.
• Model plaque studies provide insights into mineral dynamics relevant to dental health.