Saliva Flow, pH, Buffer Capacity, and Colonization by Streptococcus mutans during and after Radical Radiotherapy of Head and Neck Tumours

Abstract

Background: How does oral health (saliva pH, buffer capacity, and colonization with Streptococcus mutans) change because of reduced salivary flow during and after radical radiotherapy of head and neck carcinoma dependent on ipsilateral or bilateral parotid irradiation? Patients and Methods: 20 consecutive patients who were radically irradiated because of head and neck carcinomas were studied. They were evaluated before radiotherapy, weekly during therapy, and 6 weeks after the end of treatment. Flow rate, pH and buffer capacity of saliva, and colonization with S. mutans were tested. Results: Stimulated saliva secretion rate dropped in the first radiotherapy week in both groups (p < 0.006). This effect was more pronounced in patients with bilateral parotid gland radiation (BPR) in comparison with unilateral parotid gland radiation (UPR). Depending on dose saliva production declined exponentially up to the end of treatment. No rebound was found up to 6 weeks after the end of therapy, a trend towards a further saliva production was observed. Stimulated saliva was significantly diminished when compared to production before the start of treatment (p < 0.003 for UPR and p < 0.001 for BPR). Buffer capacity was reduced parallel to the saliva deficit. The pH of saliva decreased from a mean of 7.3 before treatment to 6.3 at the end of radiotherapy and did not recover for patients with BPR. For patients with UPR, the pH decreased from a mean of 7.8 to 7.4 and remained constant. Colonization with S. mutans increased during treatment and stayed high after the end of radiotherapy. Conclusion: Saliva production is exponentially reduced during radiotherapy, starting in the first week of treatment. Recovery is not observed up to 6 weeks after therapy. Buffer capacity and pH decline during radiotherapy in relation to saliva loss. Colonization by S. mutans increases markedly during radiotherapy and remained high afterwards.