## 4 Discussion
In our pilot study, the values of TNF-\(\alpha\) in implant patients were similar to those measured in healthy patients, and the biomarker was not correlated to peri-implant bone loss. The oxidative stress, expressed by shifting the equilibrium between production or activation of free radicals and the antioxidant defenses of the host, in favor of the first one, will potentially lead to the damage of host tissues [15]. Normal saliva contains enzymatic antioxidants such as superoxide dismutase, glutathione peroxidase, peroxidase, catalase, as well as non-enzymatic antioxidants: vitamins C and A, uric acid, albumin and glutathione, among others, with an important role in neutralizing free radicals [14]. The imbalances in the levels of free radicals, reactive oxygen species and antioxidants in saliva may play an important role in the onset and development of periimplantitis. Therefore, total antioxidant activity was determined in the saliva of the subjects enrolled in Group 1 and Group 0 (reference) using the \"total antioxidant status (TAS)\" kit produced by Randox. The results showed that both groups, implant patients and the healthy controls, included in the study have normal or lowered values of total antioxidant activity in saliva. However, the lowest TAS was noticed in patients 4 and 7 of Group 1. These two patients registered a significant peri-implant marginal bone loss at one year. Additionally, overall, a strong negative correlation was found between marginal bone loss and TAS (Figure 4). This is in accordance with the study published by [PERSON] and coworkers [14] on total antioxidant activity in the oral cavity before and after periodontal non-surgical treatment. The authors found correlations between clinical periodontal parameters and the level of salivary antioxidants. They demonstrated the importance of TAS assessment in saliva for monitoring of periodontal disease. Continuous secretion and contact with the oral environment reflect a remarkable accuracy in describing all events in the oral cavity, both at the cellular and molecular level [14]. Lactate dehydrogenase (LDH) is an essential enzyme, detectable in normal conditions in the cytoplasm of almost every cell of the human body, being a catalysator of lactate production via pyruvate during anaerobic glycolysis [13]. Its extracellular presence is always related to cell necrosis and tissue breakdown, being a useful biomarker for periodontal disease diagnosis and monitoring [48]. In the present study, the lower levels of LDH in Group 1, implant patients, similar to the mean values measured in Group 2, worked in parallel, reflecting the absence of tissue destruction. No correlation between bone resorption and LDH was noticed. In spite of the limitations of the present preliminary study, and the lower number of enrolled patients, the strong correlation between marginal bone resorption and total antioxidant status (TAS) in saliva and some proinflammatory cytokines (IL-6 and IL-8) suggests that the application of these simple salivary tests could be associated with the occurrence of complications such as peri-implant bone loss. Low-cost point-of-care devices could be developed to assess patients before dental implants' insertion, and the ones with low TAS values or increased proinflammatory cytokines levels will be advised to have more regular follow-ups for a close monitoring and prevention of more severe complications. These markers assessed in the present pilot study were shown to be particularly useful in monitoring peri-implant bone loss, especially IL-6, IL-8 and TAS. However, multicenter studies on larger samples and different implant brands are required for more conclusive results.