Investigation of Salivary Function and Oral Microbiota of Radiation Caries-Free People with Nasopharyngeal Carcinoma

Abstract

Radiation caries have been reported to be correlated with radiotherapy-induced destruction of salivary function and changes in oral microbiota. There have been no published reports detailing patients who have remained radiation caries-free following radiotherapy for nasopharyngeal carcinoma. The aim of this study was to investigate the relationship between salivary function, oral microbiota and the absence of radiation caries. Twelve radiation caries-free patients and nine patients exhibiting radiation caries following irradiated nasopharyngeal carcinoma were selected. V40, the dose at which the volume of the contralateral parotid gland receives more than 40 Gy, was recorded. Stimulated saliva flow rate, pH values and buffering capacity were examined to assess salivary function. Stimulated saliva was used for molecular profiling by Denaturing Gradient Gel Electrophoresis. Mutans streptococci and Lactobacilli in saliva were also cultivated. There were no significant differences in V40 between radiation caries-free individuals and those with radiation caries. Compared with normal values, the radiation caries-free group had significantly decreased simulated saliva flow rate, while there were no significant differences in the saliva pH value and buffering capacity. Similar results were observed in the radiation caries group. There was no statistical difference in microbial diversity, composition and log CFU counts in cultivation from the radiation caries-free group and the radiation caries group. Eleven genera were detected in these two groups, among which Streptococcus spp. and Neisseria spp. had the highest distribution. Our results suggest that changes in salivary function and in salivary microbiota do not explain the absence of radiation caries in radiation caries-free individuals.

Effect of Radiotherapy on Oral Microflora of Patients with Head and Neck Malignancies

“…Notably, authors did not detect any significant decrease in pH value and buffering capacity of the stimulated saliva when compared with normal values. Zhang et al (2015) reported the quantity of Streptococcus mutans and Lactobacilli were same in both the radiation caries free patients and radiation caries patients. The results were in contradiction with previously published reports possibly because all the participants in their studies had not been treated by radiotherapy and had healthy salivary function and their data showed only a weak correlation between oral microbial diversity with the absence of radiation caries.…”

“…The richness and diversity of oral ecology decreased with increased radiation dose which was gradually restored with time. Zhang et al (2015) Licensed Under Creative Commons Attribution CC BY salivary function in irradiated patients does not recover fully after 12-36 months, although the pH value and buffering capacity of saliva returns to normal after one year or more following intensity modulated radiation therapy. Further, it was concluded that population-based long term studies are required to reveal the factors for the absence of radiation caries.…”

Microbial biogeography and ecology of the mouth and implications for periodontal diseases

“…Most studies that have evaluated the microbiota of individuals experiencing significant, chronic reductions in salivary flow (known as hyposalivation) have done so largely without regard for habitat structure in the mouth; most have used rinsing samples. [49][50][51][52][53][54][55] Other work only sampled a single supragingival surface. 56 Of the studies that did sample multiple sites, such as the maxillary and mandibular molars, samples were pooled before analysis, [57][58][59] or summary data were reported for whole mouths rather than for specific sites.…”

Microbial biogeography and ecology of the mouth and implications for periodontal diseases

“…Most prior studies that have evaluated the microbiota of individuals experiencing significant, chronic reductions in salivary flow (known as hyposalivation) have done so largely without regard for habitat structure in the mouth; most have used rinsing samples [49][50][51][52][53][54][55] . Other work only sampled a single supragingival surface 56 .…”