AGE-RELATED MICROBIOLOGICAL CHANGES IN THE SALIVARY AND PLAQUE MICROFLORA OF HEALTHY-ADULTS

The effect of age on quantitative or qualitative differences in selected bacteria of dental significance and on the carriage of opportunistic pathogens and transient oral species was determined in 79 healthy, non-denture wearing individuals divided into four age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C) and greater-than-or-equal-to 80 years (group D). Samples of dental plaque and whole saliva were cultured on appropriate selective and non-selective bacteriological media. The total numbers of viable bacteria in saliva, and the prevalence of mutans streptococci in plaque and saliva were similar in all age groups. Similarly, there was no correlation between the numbers of spirochaetes in plaque and age. In contrast, statistically significantly higher mean proportions (p = 0.004), mean log10 viable counts (p = 0.001) and isolation frequencies (p < 0.01) of lactobacilli were found in the saliva of those aged greater-than-or-equal-to 70 years compared to subjects in group A. The isolation frequency (p < 0.05) and proportions (p = 0.056) of staphylococci in saliva were also higher in those aged greater-than-or-equal-to 70 years. Yeasts were isolated most often and in higher numbers from saliva in those aged greater-than-or-equal-to 80 years and the proportion of yeasts was higher after 60 years of age, but these differences were not significant in comparison with results from individuals in group A. Actinomyces spp. were commonly isolated from plaque, but there was a change, with age, in the ratio of the proportions of A. viscosus and A. naeslundii so that A. viscosus predominated in elderly subjects (groups C and D). The results suggest that genuine age-related changes in the oral microflora can be detected, particularly after the age of 70 years, which are not related to denture-wearing or disease.