Prospective study of the long term change of the oral flora after radiation therapy

Objectives: The aim of this prospective study was to evaluate the long term change in oral pathogens following radiation therapy. Methods: Twenty-two patients with planned radiation therapy (> 30 Gy) of head and neck squamous cell carcinoma were included. Before radiation therapy, after 3, 6, and 12 months samples from the deepest periodontal pocket were drawn. Five major periodontal pathogens were studied using DNA probes (Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Bacteriodes forsythus, Treponema denticola). Stimulated saliva was sampled for the microbiologic study of caries pathogens (streptococci and lactobacilli). Plaque index and decayed, missing, filled tooth surfaces (DMF-S) were recorded. Results: A normalisation of the caries bacteria is not found correlating to a significant increase in the number of affected teeth (DMF-S) from 80.7 to 88.5 after 12 months. The plaque index remained unchanged. The incidence of periodontal pathogens did not significantly change during the follow up. Conclusion: In contrast to radiation caries there seems to be no microbiological evidence for "radiation periodontitis". Despite of the intensive oral hygiene no reduction of the high number of caries pathogens is found, which leads to a high risk of tooth decay even 12 months after radiation.