The ODOR trial will be a single-centric, double-blinded, parallel-group, double-armed pilot randomized controlled trial with a non-inferiority design. The efficacy of hyperpure chlorine dioxide will be compared to chlorhexidine mouthwash. The short-term effect of the mouthwashes will be investigated in a 3-hour-long period. The primary endpoint will be the changes in the organoleptic testing scores.

Eligible patients will be randomly allocated to two groups in a 1:1 ratio. Necessary data will be collected with prespecified electronic case report forms (REDCap). The statistician will calculate the sample size at the end of the pilot investigation of the first 30-30 patients. If feasible, investigators will continue the study by enrolling more patients.

Inclusion Criteria:

• Organoleptic test score (OLS)>=2 for IOH
• Patients with at least 20 teeth
• 8 hours of scented oral hygiene product usage, 4 hours of eating, and 2 hours of drinking restriction
• on the day of investigation, restriction of alcohol, caffeine, perfume usage, and food intake with characteristic smell

Exclusion Criteria:

• Medical history of systematic and infectious diseases (e.g., hepatitis, HIV, tuberculosis).
• Antibiotic use within the month before the study's start or during the trial or any regular medication
• Extraoral halitosis (will be distinguished by observing the nasal breath)
• Eat foods (like garlic) linked to oral malodor on the day before and the sampling day, as well as wear heavily fragrant cosmetics on that day.
• Patients with removable dentures
• Smokers (Cigars, Cigarettes, Pipes, Chewing tobacco, e-cigarette, or vaping products used in the last month)