Growth characteristics and acid production of oral isolates of Candida albicans and Candida glabrata in glucose supplemented and glucose‐free, pooled, human whole saliva were examined. Both Candida species exhibited sigmoidal growth curves in hatch cultures of mixed saliva, supplemented with glucose. The growth of Candida in saliva was accompanied by a rapid decline in pH from 7.5 to 3.2 over 48 h and the major acidic components initiating and sustaining this pH drop were pyruvates and acetates. These acidic metabolites may play an important role in the pathogenesis of oral Candida infections.

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Human enamel sections and slabs, mounted on a mandibular removable appliance, were worn by 5 adult subjects for a 1-week period. Plaque was allowed to accumulate on the in situ test sites and on the adjacent natural dentition. At the end of the experimental period, the plaque microflora associated with (1) the enamel sections, (2) the enamel slabs, and (3) the acrylic base of the appliance test site was compared with that obtained from lingual and interproximal areas of the lower molar teeth. In addition, the acid anion and pH profiles of plaque obtained from both the exogenous and natural tooth surfaces were also determined. Although some quantitative differences were found between the proportions of isolates obtained from the different enamel surfaces, qualitatively the microflora was very similar, and no significant differences were found in the plaque lactate/acetate ratios or pH measurements following a sucrose mouthrinse. Thus, human tooth specimens mounted on the intra-oral device produced a plaque ecosystem similar to that present on the adjacent natural dentition, suggesting that the model is suitable for studies on early plaque development and the microbiology of enamel demineralization.

The microbiological species and acid/anion profiles of the plaque-like material which accumulates on exposed surfaces of enamel sections mounted in the experimental troughs of the previously described in situ caries appliance were studied. Each experiment lasted 1 week and the volunteers’ diet and oral hygiene patterns were unaltered, except that interproximal plaque was allowed to accumulate in an interproximal space adjacent to one of the troughs. The appliance was removed once per day to facilitate cleansing of the lower lingual aspects of the natural dentition. The acid/anion profiles of the appliance samples were similar to plaque of equal maturity from the adjacent interproximal site. Qualitatively the microbiological species recovered from the natural and appliance plaque were similar and within the normal range for 7- to 9-day natural plaque. When the composition of appliance and natural plaque was compared some quantitative differences were found. Thus it would seem that the previously reported de- and remineralisation investigations using this appliance were carried out under the influence of an ecosystem similar to that of an adjacent interproximal site of the natural dentition. In addition, this appliance should provide a means for the study of the microbiology and biochemistry of early enamel caries.