The goal of this clinical trial is to compare the effectiveness of 0.15% guava (Psidium guajava) leaf extract mouth rinse with 0.2% Chlorhexidine (CHX) mouth rinse in reducing plaque accumulation, gingival inflammation, and oral microbial load in participants with plaque-induced chronic moderate or severe gingivitis. Half of the participants will receive guava leaf extract mouth rinse, and the other half will receive Chlorhexidine(CHX).

Plaque-induced gingivitis is one of the most prevalent oral health problems worldwide and, if not addressed, can progress to periodontitis with irreversible loss of supporting tissues. Although mechanical plaque control through tooth-brushing and flossing is essential, many individuals do not achieve adequate plaque removal, so antimicrobial mouth rinses are commonly prescribed as adjuncts. The standard 0.2 % chlorhexidine (CHX) rinse is effective yet limited by tooth staining, taste alteration, and mucosal irritation, prompting interest in safer natural options. Psidium guajava (guava) leaf extract contains flavonoids, tannins, and other bioactive compounds with documented antimicrobial, anti-inflammatory, and antioxidant properties and has shown promise as a natural oral-care agent. This clinical trial will be conducted in the Out-patient Department and will enrol 160 adults with plaque-induced chronic moderate or severe gingivitis selected by purposive sampling method. After baseline non-surgical periodontal therapy, participants will be allocated to an intervention group that receives a 0.15 % guava-leaf extract mouth rinse or to a control group that receives a 0.2 % Chlorhexidine(CHX) mouth rinse; each participant will rinse with 10 mL twice daily, 30 minutes after brushing, for three months. Plaque Index (Turesky modification of Quigley-Hein) and Gingival Index (Löe & Silness) will be recorded at baseline, one month, and three months to gauge changes in plaque accumulation and gingival inflammation. To explore antimicrobial performance, the study will determine zones of inhibition and minimum inhibitory concentration (MIC) values for each rinse. Participants will also complete structured questionnaires on taste, staining, burning sensation, and overall acceptability, and any adverse events will be documented. Findings from this trial will clarify whether guava-leaf mouth rinse offers clinical and antimicrobial benefits comparable to, or better than, Chlorhexidine(CHX) while avoiding its common side-effects, potentially providing a locally sourced, culturally acceptable, and affordable adjunct for managing gingivitis in Bangladesh and similar settings.

Inclusion Criteria: • Participants with a minimum of 24 functional teeth.

• Presence of Plaque induced chronic moderate to severe form of gingivitis.
• Participants within the age group of 18 to 35 years.
• Willing and able to comply with all study procedures.

Exclusion Criteria: • Pregnant or lactating women.

• Systemically compromised people; subjects with removable or fixed orthodontic appliances or prosthesis.
• People who were prescribed antibiotics or inflammatory drugs in the past 1 month.
• History of smoking or any form of tobacco use.
• History of allergic reactions to Chlorhexidine or Guava.
• Severe systemic conditions that could contraindicate participation in the study.