## 4 Discussion  
Saliva is one of the most important body fluids. It performs a number of vital functions, including ensuring a humid environment in the mouth, participating in water regulation, pre-digestion, protecting oral cavity structures from damage, acting as an antimicrobial agent, remineralising enamel, and participating in the perception of taste or pronunciation. Its composition and properties determine systemic homeostasis, and fluctuations in certain parameters enable it to be useful as a diagnostic marker for a number of pathologies and as a screening and treatment tool for oral squamous cell carcinoma, for instance [39]. It is very important to be able to test inflammatory markers in a non-invasive way by testing a saliva sample. Until now, the most common way to test inflammatory biomarker levels has been from a blood serum sample, which involves venipuncture and trauma, which is an invasive procedure and involves qualified personnel, laboratory equipment, and significant financial resources. In contrast, saliva collection is non-invasive, stress-free, and painless and provides an effective alternative diagnostic method [40]. A range of scientific papers that have recently been published discusses the potential use of IL-6 and CRP in the monitoring and early diagnosis of oral diseases. A study by [PERSON] et al. [41] evaluated IL-6 among a large group of 100 patients with potentially malignant lesions (PML) in the oral cavity, 100 diagnosed oral squamous cell carcinoma (OSCC) cases, and 100 controls. Among other things, it showed a twofold to threefold higher level of inflammatory markers in saliva than in serum in those patients with diagnosed OSCC when compared with PML and a group of healthy subjects, demonstrating 96% specificity and 99% sensitivity for IL-6 in saliva in distinguishing PML from OSCC. A study by [PERSON] et al. [19] assessed the levels of a variety of pro-inflammatory cytokines in 22 edentulous patients who presented with clinical mucositis or peri-implantitis. Assessing a broad panel of markers, including, as in our study, IL-6, showed that the total IL-6 levels tended to be higher in patients with peri-implantitis in relation to a comparison group that only manifested mucositis around the implants. This demonstrated that the level of severity of the inflammatory reaction developing around the implant is reflected in IL-6 levels. A pilot study by [PERSON] et al. [42] on seven patients with implants, compared to three patients in the control group, assessed the levels of total antioxidant status (TAS), amounts of IL-6, IL-8, and TNF-\(\alpha\) (tumour necrosis factor), and salivary lactate dehydrogenase (LDH) levels in correlation with bone loss around the implant over one year. Two patients in the study group had the lowest TAS levels, the highest IL-6 and IL-8 levels, and by far the highest marginal bone loss (1.0 and 0.85 mm at one year in relation to results in the range of 0.02-0.08 mm in the other implant patients). Admittedly, no strong assumptions can be drawn on such a small group; however, the authors did give consideration to screening implant patients using saliva biomarkers. Those with low TAS values or elevated levels of pro-inflammatory cytokines should undergo more frequent follow-up visits for close monitoring and the prevention of more severe complications. A study by [PERSON] et al. [43] published in May of 2023 highlights the role of point-of-care tests for the detection of salivary levels of cytokines (including IL-6) as an important tool for early diagnosis and timely treatment of inflammatory-based diseases such as periodontitis. The SPR-POF biosensor solution was presented, which allows for detecting IL-6 levels from 40 pM to 2 nM, while the GNG biosensor was designed to detect IL-6 range from 680 nM to 25 fM. The devices have applications in the diagnosis of plasma and salivary concentrations, which appears to be crucial for monitoring an individual response to a specific therapy for a particular disease.