Saliva, Salivary Micro-organisms, and Oral Health in the Home-dwelling Old Elderly-A Five-year Longitudinal Study

Abstract

High scores of chair-side salivary microbial tests have been found to be related to an increased prevalence and incidence of coronal and root caries. Many elderly face an increased risk of the growth of oral microbes, and previous studies have reported high salivary microbial counts in elderly populations. The aim of this follow-up study was to compare, at five-year intervals, stimulated salivary flow rates with the numbers of selected salivary micro-organisms (mutans streptococci, lactobacilli, and yeasts) in a group of home-dwelling elderly in Helsinki. A further aim was to study the influence of baseline microbial counts on five-year root caries increments and rates of tooth loss. The baseline study population was comprised of 270 subjects who were all participants in the population-based Helsinki Aging Study. Salivary flow rates and microbial conditions were determined as part of their dental examination at the Institute of Dentistry, University of Helsinki, in 1990-1991. Of these subjects, 110 underwent a follow-up examination in 1995-1996. Commercially available kits (Dentocult SM strip mutans® for mutans streptococci, Dentocult LB® for lactobacilli, and Oricult N® for yeasts) were used for the enumeration of micro-organisms, after the collection of paraffin-wax-stimulated whole saliva. The stimulated whole saliva flow rates of the subjects were significantly lower at the follow-up than at baseline (paired t test, difference -0.16 mL/min; p < 0.05), whereas buffer capacity was higher (paired t test, difference 0.19 on a three-unit scale; p < 0.05). Apart from lower salivary lactobacilli counts at follow-up (paired t test, difference -0.44 CFUs/mL of saliva; p < 0.001), no changes were found in salivary microbial levels. Salivary microbial counts were clearly associated with the subjects' dentition types: More denture-wearers had high microbial counts than persons with natural dentitions. None of the salivary factors correlated with the root caries incidence or the number of teeth lost during the five-year follow-up.