Background: Ventilator-associated pneumonia (VAP) is a frequent, morbid complication among mechanically ventilated adults. Oral hygiene strategies, chlorhexidine (CHX), povidone-iodine, toothbrushing, aim to reduce oropharyngeal colonization and aspiration. High-quality syntheses suggest benefit for CHX, but effects on patient-centred outcomes and across ICU populations remain debated. Objective: To systematically summarize randomized and prospective clinical studies evaluating oral hygiene interventions for VAP prevention in adults receiving invasive ventilation. Methods: Following PRISMA principles, we included original clinical trials, extracted study design, population, interventions, and clinically relevant outcomes (VAP, mortality, ventilation/ICU duration), and narratively synthesized findings without meta-analysis (heterogeneous interventions/outcomes). Results: Nine included studies (randomized and prospective) evaluated CHX (rinse/gel or paste), toothbrushing (manual/electric), and povidone-iodine, primarily in mixed ICUs, surgical ICUs, and cardiac surgery settings. Several trials demonstrated reduced VAP with CHX-based oral decontamination (including 2% CHX±colistin and pre operative mouthwash), while multiple toothbrushing trials (manual/electric) did not show additional benefit over antiseptic care alone. Conclusions: Across heterogeneous ICU populations, CHX-based oral care generally reduces VAP incidence, whereas adding toothbrushing alone does not consistently confer extra benefit. Findings align with contemporary meta-analyses and guidelines, though effects on mortality and lengths of stay remain uncertain.