Subclinical Oxidative and Matrix-Regulatory Alterations Associated with Cigarette Smoking and E-Cigarette Use in Periodontally Healthy Adults: A Cross-Sectional Study

Abstract

Background/Objectives: Cigarette smoking is a well-established risk factor for periodontal tissue damage caused by oxidative stress and increased proteolytic activity. Electronic cigarettes (e-cigarettes), marketed as less harmful alternatives, deliver nicotine and reactive compounds that may similarly disrupt periodontal health. However, their molecular effects on clinically healthy periodontal tissues remain unclear. This study aimed to compare oxidative stress-related and matrix-degradative biomarkers in the gingival crevicular fluid (GCF) of cigarette smokers (CS), e-cigarette (EC) users, and non-smokers (NS), and to examine the relationships among these markers. Methods: Sixty individuals, who were systemically and periodontally healthy (20 CS, 20 EC, and 20 NS), were examined. Clinical parameters, including probing depth (PD), clinical attachment level (CAL), plaque index (PI), and bleeding on probing (BOP), were recorded. GCF samples were analyzed for reactive oxygen species (ROS), matrix metalloproteinase-9 (MMP-9), and forkhead box protein O-1 (FOXO-1) using ELISA. Initial group comparisons were descriptive, followed by analysis of covariance (ANCOVA) to adjust for age; PI and PD were included as covariates in separate models. Correlations were assessed using Spearman's analysis. Results: PD was significantly higher in both EC users and CS compared with NS (p = 0.022). MMP-9 levels were significantly higher in CS than in EC users and NS (p < 0.05), while FOXO-1 concentrations were significantly lower in CS compared with NS (p = 0.0227). ROS levels did not differ significantly among groups (p > 0.05). After adjustment for age, PI, or PD, group differences in MMP-9 and FOXO-1 remained statistically significant, whereas ROS levels remained comparable. FOXO-1 demonstrated positive correlations with ROS and MMP-9 within exposure groups; these associations were considered exploratory. Conclusions: In this cross-sectional study, CS and EC use were associated with altered matrix-regulatory biomarker profiles in clinically healthy periodontal tissues, independent of age and periodontal indices. Causal or temporal inferences cannot be drawn, and longitudinal studies are needed to clarify the long-term periodontal implications of these findings.