Microflora in oral ecosystems and salivary secretion rates - A 3-year follow-up after radiation therapy to the head and neck region

Objective: Results indicate that late improvements of radiation therapy (RT) in the head and neck region may diminish the long-term effects on salivary glands and oral microflora. The aim was therefore to analyze salivary secretion rates and oral microflora over time in RT subjects. Design: Twelve dentate subjects (28 +/- 2 teeth) and 12 controls were included. A clinical examination was performed and the salivary secretion rates were determined. Microbial samples, analyzed using cultivation technique, were collected from the soft tissues, supragingival plaque and gingival crevice region. Results: Compared with the controls, the RT group (n = 11) had 3 years post RT higher numbers and proportions of lactobacilli (p < 0.001 and p < 0.01) and Candida albicans (p < 0.01 and p < 0.05) in the supragingival plaque, higher numbers of enterococci in the vestibulum in the molar region and on the tongue (p < 0.05 for both), a lower total count (p < 0.001) and lower numbers of streptococci, Streptococcus salivarius and Fusobacterium nucleatum (p < 0.01) on the tongue. Although both stimulated and unstimulated salivary secretion rates were increased over time, the proportion of microorganisms associated with oral health decreased, and microorganisms associated with oral disorders increased. Despite a comparable oral hygiene, it was only the 27% who had a stimulated salivary secretion rate >= 1.0 ml/min and a buffering capacity >= 6.0, where a recovery of the flora could be seen. Conclusion: The results indicate that regaining a normal, stimulated salivary secretion rate and buffering capacity are prerequisites to regaining an oral flora associated with good oral health. (C) 2015 Elsevier Ltd. All rights reserved.