Dry mouth is a common feature in the elderly, but it is not clear what proportion of incidences are related to functional disturbances and whether age per se and gender play a role. The aim of this study was to determine the effects of age and gender on salivary flow rates. The effect of age on unstimulated (resting) whole and stimulated parotid saliva flow rates was determined in 116 unmedicated, healthy individuals. The subjects were divided into four age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C), and 80 years and over (group D). A significant decrease in the secretion rates of unstimulated whole saliva in relation to age was observed in the study population (p < 0.001). However, the flow rates of stimulated parotid saliva were not significantly different in the four age groups. Females had significantly lower mean flow rates than males for both unstimulated (resting) whole saliva (p < 0.005) and stimulated parotid saliva (p < 0.05). In the study as a whole, significant negative correlations were found between either the DMF index (decayed, missing, and filled teeth) or the DMFS index (decayed, missing, and filled tooth surfaces) and the flow rates of unstimulated whole saliva (p < 0.02), but no relationship to stimulated parotid saliva flow rates was apparent. The results suggest that elderly subjects have no impairment in their ability to respond to sialogogues but that resting saliva rates are significantly lower than in younger individuals and may contribute to the increase in oral mucosal diseases seen in the elderly.

Summary. 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 2 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 loglo viable counts (p = 0.001) and isolation frequencies (p < 0.01) of lactobacilli were found in the saliva of those aged 2 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 2 70 years. Yeasts were isolated most often and in higher numbers from saliva in those aged 2 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.

The effects of denture-wearing and age on the prevalence of selected bacteria of dental significance and on the carriage of opportunistic pathogens in molar plaque and whole saliva were determined in 120 healthy subjects, 41 of whom wore partial dentures. The subjects were 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). The proportions, mean log10 viable counts, and isolation frequency of yeasts and lactobacilli in saliva and plaque were consistently higher in partial-denture wearers. The proportions of staphylococci and mutans streptococci were also raised in denture wearers, but these differences did not reach statistical significance. When the data were analyzed for age effects, both yeasts and lactobacilli were found to be increased in saliva with age, but statistically significant differences were generally found only between denture wearers in group D and subjects in the control group A. The isolation frequency of yeasts from plaque was also significantly higher in denture wearers of the oldest age group (D) compared with those in group A. A. viscosus predominated over A. naeslundii in the older age groups, regardless of the presence of dentures. Enterobacteria were isolated occasionally but only from the saliva of denture wearers in group D. Spirochetes and black-pigmented anaerobes were generally found in lower numbers in denture wearers. Collectively, the data show that components of the oral microflora in adults can be independently influenced by both age and the wearing of partial dentures.

Lipid A structure is a critical determinant of the interaction between pathogens and the innate immune system. Previously, we demonstrated the presence of non-and monophosphorylated tetra-acylated lipid A structures in the outer membrane of Porphyromonas gingivalis, an agent of human periodontal disease. These modifications to lipid A structure lead to evasion and suppression of innate defenses mediated by Toll-like receptor 4 (TLR4) and cationic antimicrobial peptides. In this investigation, we examined the influence of growth temperature on P. gingivalis lipid A structure and recognition by TLR4 as an example of an environmental influence which is known to vary between healthy and diseased sites in the periodontium. We demonstrate that P. gingivalis grown at a normal body temperature produces mainly nonphosphorylated and monophosphorylated tetra-acylated lipid A structures, whereas bacteria grown at 39°C and 41°C intended to mimic increasing levels of inflammation, producing increasing proportions of monophosphorylated, penta-acylated lipid A. The temperature-dependent alteration in lipid A renders the bacterium significantly more potent for activating TLR4 and more susceptible to killing by ␤-defensins 2 and 3. This is the first report of a lipid A remodeling system linked to temperature shifts associated with a deregulated inflammatory response. Temperature elevation at sites of inflammation in the periodontium may be a significant environmental regulator of the lipid A modification systems of P. gingivalis, which will influence the interaction of this organism with the innate host defense.Lipopolysaccharide (LPS) is the major constituent of the outer leaflet of the outer membrane of all Gram-negative bacteria, where it plays an important structural role as well as mediates interactions with the environment. It consists of three regions, as follows: lipid A, which is embedded in the outer membrane and is responsible for the proinflammatory endotoxin properties of the molecule, and the core oligosaccharide and O-polysaccharide side chain, which both extend from the surface of the cell and mediate external interactions. Lipid A is considered to be an archetypal microbe-associated molecular pattern (MAMP), a molecular motif found in a range of microbes which the innate immune system recognizes as nonself through an extensive repertoire of evolutionary conserved receptors. Recognition of lipid A by Toll-like receptor 4 (TLR4) facilitates a robust proinflammatory response by the host immune system that promotes clearance of the bacteria from protected tissues (24). Furthermore, phosphate groups on lipid A bestow an overall negative charge to the outer surface of Gram-negative bacteria, which promotes the selective membrane binding of host cationic antimicrobial peptides and, hence, bacterial killing at mucosal epithelial surfaces (3).Lipid A is a ␤-1,6-linked D-glucosamine disaccharide phosphorylated in the 1 and 4Ј positions and N-and/or O-acylated at positions 2, 3, 2Ј, and 3Ј with various amounts of fatty acid...