Introduction: Chronic gingival diseases are primarily caused by microorganisms present in dentobacterial plaque, which can be controlled through mechanical methods like brushing or chemically using mouthwashes. The Autonomous University of Baja California has developed a chitosan-based molecule enriched with colloidal silver nanoparticles (EPX® Biomolecule), which acts as an antiseptic and is administered topically. Objective: This study aims to evaluate the efficacy and safety of EPX® Biomolecule mouthwash in the treatment of chronic gingivitis. Methods: An experimental study, phase I clinical trial, was conducted involving a randomized sample of 50 adult patients diagnosed with chronic gingivitis, treated at the Santé Dental Clinic from January to December 2022, following the acquisition of informed consent. The study comprised a case group of 25 patients treated with EPX® Biomolecule mouthwash, compared against a control group of 25 patients receiving 2% chlorhexidine oral rinse. Statistical analysis was performed using Student's t-test, with a significance level set at p<0.05. Results: The majority of participants were women (54%), under 30 years of age (92%), students (58%), and had completed high school (82%). At 15 days, both treatments exhibited similar effects; however, chlorhexidine showed a marginally better response at 30 days, which was statistically significant for the Gingival Index (p = 0.01) and the Hemorrhagic Index (p = 0.01). No significant differences were observed in dentobacterial plaque levels, although adverse reactions were noted with chlorhexidine. Conclusions: Both treatments effectively reduced bleeding and gingival edema, with chlorhexidine demonstrating improved outcomes at 30 days. There were no differences in plaque control, and an isolated adverse reaction was associated with chlorhexidine.