Oral microbial flora at hyposalivation

Abstract

Purpose: The overall objective of the present thesis was to study the effect of salivary flow rate on the oral microbial flora and on the saliva composition in groups with hyposalivation of different origins. Material and methods: The oral flora was analysed in rinsing samples from dentate subjects with hyposalivation due to radiation therapy in the head and neck region (RT group), primary Sjögren's syndrome (pSS group), secondary Sjögren's syndrome (sSS group), neuroleptic treatment (Neuro group), medication or of unknown origin (Unknown group). The oral microflora was also analysed in specific sites, on the dorsum of the tongue, buccal mucosa, vestibulum in the molar region, supragingival tooth surface and in the gingival crevice region in subjects with pSS. The micro-organisms registered in rinsing samples were: the total number of micro-organisms growing anaerobically, the total number of streptococci, mutans streptococci, Lactobacilllus spp., Fusobacterium nucleatum, Prevotella intermedia/Prevotella nigrescens, Candida albicans, Staphylococcus aureus and enterics. In samples taken from specific sites also Actinomyces spp., enterococci, Porphyromonas gingivalis and Actinobacillus actinomyctemcomitans were registered. The unstimulated and the stimulated salivary secretion rates and the pH and buffer capacity in stimulated saliva were determined. Lactoferrin, amylase, mucin MUC5B, bicarbonate, sodium, potassium, calcium and phosphate were analysed in stimulated whole saliva. A clinical examination with registration of the status of the mucosal membranes, number of teeth and fillings, bleeding on probing and presence of plaque along the gingival margin was performed. Results: Compared with controls with normal salivary secretion, a decreased bicarbonate concentration was seen in all hyposalivation groups. This probably explains the low numbers of micro-organisms associated with gingival inflammation, which was a common feature for all the groups with hyposalivation as was high levels of Lactobacillus spp., associated with an acidic milieu and caries. The characteristic changes in the pSS group, were the two times higher lactoferrin concentration and the five times higher albumin concentration, indicating serum leakage, and that high numbers of mutans streptococci were frequently detected. In the RT group, the proportionally much larger increase in lactoferrin concentration than in albumin concentration, indicates an acute inflammation in the oral tissues. The RT group was also the only group with a significant decrease in amylase concentration suggest an impaired activity of the parotid glands. This group also had the largest increase in frequency, number and proportion of Lactobacillus spp., and C. albicans, associated with an acidic milieu and mucosal infections. Mutans streptococci were not detected in 29% of the subjects and in high proportions in 29%. The characteristic feature for the Unknown group was that mutans streptococci were detected in all subjects. Otherwise this was the group most similar to the controls regarding microbial flora, saliva proteins and electrolytes analysed. The Neuro group was the only group with dental plaque visible without staining and with the highest proportion of surfaces with bleeding on probing. The characteristic feature for the Neuro group was an increase in amylase, suggesting that more saliva came from the parotid glands than from the submandibular glands. The very low bicarbonate concentration in the Neuro group suggests salivary gland dysfunction. The Neuro group had the highest total microbial count and the lowest proportion of streptococci of all the hyposalivation groups. Conclusion: The present series of studies indicate that the oral microflora and the whole saliva composition are affected differently in subjects with different reasons for hyposalivation.