Radiation Therapy’s Impact on Salivary Amounts, pH and Mouth Opening

Objectives: Cancer treatment has been shown to cause multiple side effects including xerostomia and trismus due to salivary glands and muscle damage during radiotherapy. However, the use of intensity modulated radiation therapy (IMRT) to replace more invasive conventional beam radiation therapy means that more healthy tissue sparing can now be achieved. No study has been published on IMRT’s effect on salivary pH and mouth opening. The aim of the study was to determine the impact of IMRT on salivary rates, pH and mouth opening.

Methods: 36 patients diagnosed with cancer had their whole resting saliva, stimulated saliva, respective pH, and maximum mouth opening at baseline documented, upon first being seen at the BC Cancer Agency prior to receiving IMRT, and subsequently 3 months post IMRT.

Results: Pre and post-treatment salivary volume, pH, and mouth opening were compared using paired t-tests. Resting saliva was significantly reduced post-treatment, t(35) = 3.994, p < 0.0005. Stimulated saliva was also significantly reduced, t(33) = 4.980, p < 0.0005. There was no significant difference in resting or stimulated saliva pH before and after treatment, t(26) = 1.616, p = 0.118, and t(30) = 1.239, p = 0.225 respectively. Mouth opening distance was significantly lower after treatment, t(30) = 3.058, p = 0.005.

Conclusions: IMRT can cause a statistically significant decrease in stimulated saliva volume, although no significant decrease was observed in resting salivary volume. Resting and stimulated salivary pH did not appear to have been impacted by IMRT. At the 3-month mark, a statistically significant decrease in maximum mouth opening can already be observed. Although limited in sample size, this study does highlight the need for early trismus therapy on cancer patients, and encourages us to further study the impact of IMRT on xerostomia and oral health in order to propose better strategies for treatment.