This cross-sectional observational study aims to investigate the effects of e-cigarette use on oxidative and matrix-degrading pathways in periodontally healthy individuals. Gingival crevicular fluid biomarkers, including matrix metalloproteinase-9 (MMP-9), reactive oxygen species (ROS), and forkhead-box-1 (FOXO1), will be analyzed to compare the biochemical and inflammatory responses among three groups: e-cigarette users, conventional cigarette smokers, and non-smokers. The study seeks to clarify whether e-cigarette use induces subclinical inflammatory or proteolytic activity in oral tissues comparable to that of traditional smoking.