Nitric oxide (NO) is considered a regulator of bone response to mechanical stress that mediates adaptive bone formation, the pathological effects of lipopolysaccharides (LPS), tumour necrosis factor (TNF), interleukin 1 (IL-1) and other cytokines; regulates leukocytes and epithelial cell adhesion; inhibits T cell proliferation; and enhances natural killer (NK) cell activity, as well as other immune-related processes. The aim of the current study was to test the potential use of salivary NO as a biomarker of bone response that is specific and sensitive to local changes, following the application of different types of dental appliances. Material and methods: Salivary NO was determined in 30 patients divided into three groups with 10 participants each: control (C), fixed metal braces group (M), and aligners group (A). Salivary NO was determined four times in each group (before the procedure, at 2 weeks, 30 days, and 60 days after the procedure) using ELISA and rapid semi-quantitative assay with Nitric Oxide Saliva Test Strips (Berkeley, CA, USA). The mean results were compared with the ANOVA test, and the Pearson correlation index was calculated. The results show a significant increase in salivary NO levels by both methods only in the metal braces group, which is suggestive of oxidative damage, increased invasiveness, and bone response to metal braces. In conclusion, our study showed that metal brackets lead to a significant temporary increase in oral oxidative stress as an adaptive reaction to the presence of foreign bodies in the oral cavity. The subsequent concentration decrease at 60 days suggests a normalization of the body’s response to foreign bodies.