Changes in Salivary 8-iso-Prostaglandin F2α after Six Months of Orthodontic Appliance Wear: A Prospective Paired Study

Orthodontic appliances may influence oral redox homeostasis through a combination of mechanical forces, biofilm alterations, inflammatory responses, and long-term exposure to dental materials and corrosion products. These factors may contribute to oxidative stress within the oral cavity, particularly during the initial phases of orthodontic treatment. F2-isoprostanes, and especially 8-iso-prostaglandin F2 α (8-iso-PGF2 α), are considered reliable biomarkers of lipid peroxidation and oxidative stress in vivo. Saliva represents a practical and non-invasive biological matrix for monitoring local biochemical changes associated with orthodontic therapy [1,2,3,4,5]. The aim of the present study was to evaluate changes in salivary 8-iso-PGF2 α levels before orthodontic appliance placement (T0) and six months after placement (T1) in patients undergoing orthodontic treatment. A prospective paired longitudinal study was conducted in patients receiving orthodontic appliances. A total of 137 participants provided baseline (T0) saliva samples, and 122 completed the 6-month follow-up with paired samples at T0 and T1. The planned one-month follow-up could not be included due to participant attrition associated with repeated saliva sampling and technical failure of the analytical equipment. Consequently, the present analysis focuses on paired baseline and six-month measurements. Unstimulated whole saliva was collected under standardized conditions. Salivary 8-iso-PGF2 α concentrations were quantified using liquid chromatography–tandem mass spectrometry (LC–MS/MS) with selective reaction monitoring and internal standardization, following salt-assisted protein precipitation and liquid–liquid extraction [6]. Values below the analytical limit of detection were imputed as half the detection limit (LOD/2, 0.5 pg/mL). Data are presented as median and interquartile range (IQR). Paired comparisons were performed using the Wilcoxon signed-rank test, and effect size was calculated as $$r=|z|/\sqrt{n}$$. Median salivary 8-iso-PGF2 α concentration decreased from 6.42 pg/mL (IQR 4.23--10.14) at baseline to 4.60 pg/mL (IQR 2.94–7.05) six months after appliance placement. The reduction was statistically significant (Wilcoxon W = 1891, p < 0.001) and was associated with a moderate effect size (r = 0.43). In the paired cohort (n = 122), 35% were males and 65% females, with ages ranging from 8 to 63 years. Most participants (85/122; 69.7%) were treated with appliances containing metal elements. The decrease in 8-iso-PGF2 α remained statistically significant within age- and sex-based subgroups. Salivary 8-iso-prostaglandin F2 α concentrations were significantly reduced six months after orthodontic appliance placement compared with baseline. These findings indicate a decrease in oral lipid peroxidation over time. Measurement of salivary 8-iso-PGF2α by LC–MS/MS represents a reliable and non-invasive approach for monitoring oxidative stress in orthodontic patients.