The focus of this study is on two types of mouthwashes - one containing a chlorhexidine (CHX) at 0.2% (CHX), and the other one containing CHX at a lower concentration of 0.12% with cetylpyridinium chloride (CPC). Both mouthwashes are used to help in the treatment of gum disease. CHX has been known for a long time for its effectiveness against plaque and mouth inflammation. It could inhibit and even kill them. However higher concentrations of CHX comes with unwanted side effect including altered taste, teeth staining and irritation in the mouth. Interestingly, these side effects seem to occur less frequently when a lower concentration CHX solution is used. CPC also combats bacteria by adhering quickly to the surfaces inside your mouth, although it has less substantivity than CHX, it has been shown to reduce plaque and gum inflammation effectively, and it typically causes fewer side effects than CHX. We hypothesize that this new formulation of CHX 0.12%+CPC mouthwash is non-inferior to CHX 0.2% in terms of its anti-plaque and anti-inflammatory properties while presenting with less side effects after 21 days of use. Microbiological samples and fluids from periodontal pockets will be collected before and after treatment for analysis of microbiological effects.

• Aim: To compare the effects of 2 formulations of antiseptics on clinical efficacy (reduction of gingival inflammation and plaque) and oral microbiome when used as an adjuvant in periodontal treatment.
• Hypothesis: HA: The study mouthwash (CLX 0.12% + CPC 0.05%) when used as an adjunct to step 1 periodontal therapy, is non-inferior to control mouthwash (CHX 0.2%) in terms of inflammation and plaque control.
• Primary outcome: Changes in full mouth Bleeding on Probing (BoP) at 2 months after 21 days daily use of test mouthwash as an adjunct to step 1 periodontal therapy compared to active control.
• Secondary outcome:

Changes in BoP at 21 days after baseline. Changes in Löe and Silness Gingival Index at 21 days and 2 months after baseline.

Changes in modified O'Leary plaque index and Turesky modification of Quigley-Hein plaque index at 21 days, 2 months after baseline.

Changes in Tongue Coating Index and Lobene Stain Index at 14, 21 days and 2 months after baseline.

Pocket probing depth (PPD) and clinical attachment level (CAL) changes 2 months after baseline.

Subgingival microbiological changes at 21 days and 2 months after baseline. Gingival cervical fluid volume and inflammatory biomarker profile changes at 21 days and 2 months.

Taste alteration and mucosal irritation at 14 days, 21 days and 2 months after baseline.

Changes in patient-reported outcome measures at 21 days and 2 months after baseline

Inclusion Criteria:

• Consenting patients with at least 6 evaluable teeth in each quadrant, including minimum 1 molar and 1 premolar.
• Generalized stage II-III periodontitis patients.
• Baseline BOP > 25%.
• No known allergy or adverse effects to CHX or CPC
• Non-smokers, non-orthodontic patients, no concurrent or past antibiotics/medication known to affect periodontal status (i.e. calcium antagonists, phenytoin)/anti-inflammatory therapy (i.e. NASIDs) in the last 3 months, pregnant/breastfeeding, compliance to study procedures.
• ASA class I-II patients.
• Either non-diabetic or with controlled diabetes (HbA1C<7).
• Normal/Elevated blood pressure (AHA - Systolic <130mmHg; Diastolic <80mmHg).
• No radiation/chemotherapy in the past 5 years
• No immunosuppression including drug induced immunosuppression.
• No participation in other clinical studies in the last 4 weeks.
• No administration of CHX or CPC in the last 3 months
• No periodontal treatment in the last 3 months.

Exclusion Criteria:

• Unable to provide written consent.
• Non-compliant study procedures.
• Patients with medical (including psychiatric) and pharmacotherapeutic histories that, in the investigator's opinion, may compromise the protocol.
• Patients requiring antibiotics prophylaxis for dental procedures.
• Patients with self-reported pregnancy or patients who are breastfeeding.
• Patients with history of use of systemic antibiotics, in combination with any form of periodontal treatment, within the past 3 months.
• Patients with uncontrolled endocrine disease.
• Patients who are not compliant with the review protocol, leading to deviation of more than 1 week.
• Patients requiring the admission of systemic antibiotics, in combination with any form of dental treatment, during the study period.

There is concern that individual participant data sharing may violate data ownership policy of the institute. Information sheet and consent form approved by local IRB did not explicitly permit data sharing beyond the scope of the current study. As such, sharing IPD could potentially infringe upon the rights and expectations of our participants, which we are committed to safeguarding.

The allocation concealment will be maintained from all parties until data analysis stage.