• Apical periodontitis induces systemic metabolic alterations. • Fourier-transform infrared spectroscopy detects biochemical signatures in urine. • Urine is more sensitive than serum for monitoring infection. • Endodontic infections impact systemic metabolic homeostasis. To investigate whether apical periodontitis induces detectable systemic biochemical alterations in a rat model using Fourier-transform infrared (FTIR) spectroscopy applied to dried urine and serum samples. Twelve male Wistar rats were randomly allocated into two experimental groups: control (C) and apical periodontitis (AP) (n = 6 per group). Apical periodontitis was induced by pulp exposure and extirpation of the first molars, with the cavities left open for 21 days to allow periapical lesion development. Blood and urine samples were collected and analysed by attenuated total reflectance FTIR spectroscopy after controlled drying on the ATR crystal surface. Mean absorbance spectra were obtained and compared between groups, focusing on spectral regions associated with lipids (2800–3000 cm⁻¹), proteins (1500–1700 cm⁻¹), phosphates (900–1200 cm⁻¹), and carbohydrates (1000–1500 cm⁻¹). Univariate analysis and principal component analysis (PCA) were performed to explore biochemical differences, and supervised classification using PCA–linear discriminant analysis (PCA–LDA) was applied to evaluate discriminant performance. Urinary FTIR spectra revealed statistically significant differences between control and AP groups within the fingerprint region (1200–900 cm⁻¹; p=0.0068), indicating alterations in carbohydrate- and phosphate-related vibrational bands. No significant differences were observed in serum samples across lipid-, protein-, or fingerprint-associated regions (p>0.05). Serum dataset exhibited better classification performance (accuracy 76.92%, sensitivity 85.71%, specificity 66.67%) compared with urine samples (accuracy 36.84%, sensitivity 44.44%, specificity 30.00%). Serum spectra demonstrated better discriminant performance than urine spectra in the PCA–LDA model. These findings support the systemic impact of endodontic infection and highlight the potential of FTIR as a non-invasive tool for investigating the biochemical interface between apical periodontitis and systemic health.
Marinho et al. (Sun,) studied this question.