A laboratory microcosm (artificial mouth) for the culture and continuous pH measurement of oral bacteria on surfaces

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Abstract
A laboratory microcosm has been designed for the cultivation of bacteria on surfaces subjected to an adjustable supply of fluids. Bacteria are grown as a microbial film on halved premolar teeth, mounted back to back. Synthetic saliva is dropped slowly over the teeth throughout experiments. A nutrient supplement is provided at regular intervals. The drops of fluid retained by the teeth can be sampled for metabolic end‐products. Alternatively, a miniature glass electrode may be set into one half of a tooth assembly to monitor the pH continuously at the stagnation site between tooth segments. Up to six replicate culture flasks and six electrodes can be accommodated in a single experiment. Satisfactory electrode performance was maintained during 66 h experiments. In initial 48 h experiments, teeth were inoculated with Streptococcus rattus BHT or ‘Streptococcus mitior’ LPA‐1 in pure culture and provided with 1% (w/v) glucose for 1 h every 6 h. Bacteria produced typical responses to glucose feeds leading to the formation of ‘Stephan’‐like curves of pH‐fall. Under these conditions, ‘Strep. mitior’ was more acidogenic than Strep. rattus and the pattern of acid production was distinct for each organism.

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