Effect of fixed orthodontic treatment on oral microbiota and salivary proteins

The aim of the present prospective comparative cohort study was to analyze changes in Streptococcus (S.) mutans and Lactobacillus in the saliva of patients with fixed orthodontics. Salivary parameters, including secretory immunoglobulin A (sIgA), myeloperoxidase (MPO) and lactate dehydrogenase (LDH), were investigated during orthodontic treatment, as well as immune response and inflammatory processes. A total of 15 patients were included and treated with fixed appliances. Whole saliva was obtained at four time-points: Prior to bonding (T1), 3 months after bonding (T2), 6 months after bonding (T3) and 18 months after bonding (T4). Quantitative polymerase chain reaction was performed to evaluate changes in total bacteria, S. mutans and Lactobacillus DNA in saliva. ELISA was applied to measure sIgA, MPO and LDH levels. The level of total bacteria remained stable during the 18-month treatment period, and the quantity of Lactobacillus exhibited a slight but non-significant increase. S. mutans remained stable over the first 6 months and significantly increased at T4 (P<0.05), and there was a significant difference in S. mutans levels between two types of braces. A higher level of S. mutans was found in patients with conventional braces, as compared to those with self-ligating braces (P<0.05) who exhibited an unchanged level of S. mutans during this period. The amount of sIgA, MPO and LDH remained constant during the orthodontic treatment period. No correlation was detected between sIgA and bacterial quantity. In conclusion, S. mutans in patients with conventional braces increased significantly in the late period of treatment, which indicated that white spot lesions may occur after long-term orthodontic treatment. As the type of braces may be considered a latent influencing factor, self-ligating braces should be preferred. However, the effect of fixed orthodontic treatment on Lactobacillus and sIgA, MPO and LDH in the oral microenvironment was insignificant (Chinese Clinical Trial Registry no. ChiCTR-RCH-13003295).