## 5 Discussion
It was revealed that saliva secretion follows the circadian rhythm, with the lowest secretion rate occurring during sleep, and the highest rate in the late afternoon. However, most of the flow rates were measured for whole saliva or saliva from major salivary glands, but there also exist minor salivary glands, and researchers proposed that they have an important contribution also. No statistical difference was seen in the flow rates between male and female subjects, whereas other research [29] concluded that there were gender differences; it was shown that saliva flow rates had lower values in women. Higher values, compared with the controls, were recorded for patients with poor hygiene, and, in general, with a preponderant food imbalance (MSRF = 0.77 mL/min). It was indicated [30] that chemotherapy radiation induced periodontal inflammation [31], which was also suggested in our research. This could be exacerbated, even if the oral hygiene levels were good. In agreement with previous studies, we considered that it was fundamental to control plaque accumulation by related indexes in irradiated patients to prevent colonization of periodontal pockets of pathogens [32] and in patients with a decreased local defense and permanent salivary changes. All cancer patients experienced a certain degree of mucositis, but some of them had severe, advanced mucositis of grade three or four, or, more precisely, 85% of those receiving RT orally (in the case of those with advanced carcinomas, the percentage was even 100%). The lesions usually healed in about 4-7 weeks after the last dose. In our study, the prevalence of mucositis was 64.29%. Intensity-modulated radiation therapy (IMRT) in oral cancer, after the correlation observed between variables, especially mucositis and SFR. During week 2 and 5 of treatment, our results indicated that it was registered severely deteriorated the patients' quality of life and general health status, which was quantified by the Karnofsky performance status scale (KPS) [33]. Hyposalvation was identified in 78.41% of the sample and the mean radiation dose applied was 63.01 Gy (\(\pm\)9.58). Hyposalvation was associated with higher doses of radiation (\(p\) = 0.038), which had the potential to increase the chance of presenting hyposalvation by 4.25 times. In terms of this issue, concomitant chemotherapy and RT therapeutic procedures did not seem to increase the chances of hyposalvation compared to radiotherapy alone, and time elapsed since the end of radiotherapy had a protective effect, which was quantified at 75% (\(p\) = 0.025) [34]. The literature suggests [34] that salivary hypofunction and xerostomia are induced by RT in the head and neck region, depending on the cumulative radiation dose to the gland tissue and the new approaches to further reduce the dose to the parotid [35], and in particular, the submandibular and minor salivary glands, as these glands are major contributors to the lubrication of oral tissues. The way each type of radiation behaves is important in planning radiation treatments. A radiation oncologist selects the type of radiation that is suitable for each patient's cancer type and location. Radiation-induced xerostomia has been a common complication in RT of oral cancer patients, despite the advancement in RT techniques [36]. After RT, low values of SRF appear in oral cancer patients [37] due to changes in salivary gland parenchymal [38] assigned to microvascular glandular inflammation and oedema; patients have difficulties in chewing, swallowing, and speech. When radiation exposure exceeds 50 Gy the reduction in salivary flow is profound, and it dwindles over 90%, in our present study the indication value was around 60-70 Gy. Stimulated salivary flow was lowest in the cases group (MSSF = 0.51 mL/min) compared to the control group (MSSF = 1.47 mL/min). In patients with oral cancer, after RT, the low stimulated salivary flow was explained by secretion hypofunction, severe atrophy, interstitial fibrosis, and loss of parenchyma of salivary glands [39, 40].