A pilot study of the metabolomic profiles of saliva from female orthodontic patients with external apical root resorption

Background: Orthodontically induced external apical root resorption (OIEARR) is one of the most severe complications of orthodontic treatment, which is hard to diagnose at early stage by merely radiographic examination. This study aimed to identify salivary metabolic products using unbiased metabolic profiling in order to discover biomarkers that may indicate OIEARR. Materials and methods: Unstimulated saliva samples were analyzed from 19 healthy orthodontic patients with EARR (n = 8) and non-EARR (n = 11). Metabolite profiling was performed using H-1 Nuclear Magnetic Resonance (NMR) spectroscopy. Results: A total of 187 metabolites were found in saliva samples. With supervised partial least squares discriminant analysis and regression analysis, samples from 2 groups were well separated, attributed by a series of metabolites of interest, including butyrate, propane-1,2-diol, alpha-linolenic acid (Ala), alpha-glucose, urea, fumarate, formate, guanosine, purine, etc. Indicating the increased inflammatory responses in the periodontal tissues possibly associated with energy metabolism and oxidative stress. Conclusions: The effective separation capacity of H-1 NMR based metabolomics suggested potential feasibility of clinical application in monitoring periodontal and apical condition in orthodontic patients during treatment and make early diagnosis of OIEARR. Metabolites detected in this study need further validation to identify exact biomarkers of OIEARR. Saliva biomarkers may assist in diagnosis and monitoring of this disease.