This randomized, single-blind clinical trial aims to evaluate the short-term effectiveness of two different oral hygiene instruction (OHI) methods-video-assisted instruction versus traditional 3D model demonstration-on periodontal clinical parameters in patients diagnosed with gingivitis. A critical secondary objective of this study is to investigate the predictive role of patients' baseline Oral Hygiene-Related Self-Efficacy (OHSE) on the extent of clinical healing, and to assess changes in patient-reported subjective gingival health using a Visual Analogue Scale (VAS). A total of 80 patients undergoing standard Phase 1 periodontal therapy (scaling and root planing) are randomly assigned in a 1:1 ratio to either the video instruction group or the model instruction group. Periodontal clinical indices, including Plaque Index (PI), Gingival Index (GI), Probing Depth (PD), and Bleeding on Probing (BOP), alongside patient-reported outcomes, are recorded at baseline and at a one-month follow-up by a blinded examiner. The primary hypothesis is that video-based instruction is non-inferior to conventional model-based instruction in improving clinical parameters. Furthermore, the study hypothesizes that a patient's baseline self-efficacy level-independent of the educational method received-significantly predicts the reduction in periodontal inflammation and bleeding scores.