# Brief Summary (Word count: 198)

This combined observational and interventional study investigates salivary amino acid profiles and their connections to periodontal conditions, as well as how these substances change after standard non-surgical gum treatment. It recruits adults aged 20 to 50, including healthy volunteers, people with gingivitis and periodontitis. The study is approved by the institutional ethics committee with the ID WCHSIRB-D-2023-370. The main questions it aims to answer are:

Do salivary free amino acid levels differ across people with healthy gums, gingivitis and periodontitis? Are changes in salivary branched-chain amino acids related to improved gum health after treatment?

Researchers compare three groups in the observational part and track periodontitis patients to assess treatment effects. All participants go through eligibility screening, full periodontal checks and morning saliva collection. 45 participants complete only one baseline visit. Another 32 periodontitis patients receive standard therapy and return for re-examinations at 6 and 12 weeks. Saliva samples are tested for amino acid concentrations. Statistical analysis will explore the correlation between salivary markers and gum conditions. The results may aid clinical evaluation and management of periodontal diseases.

Inclusion Criteria:

• Age between 20 and 50 years old at the time of enrollment.
• Body mass index (BMI) between 18.5 and 24.0 kg/m².
• No special dietary habits (e.g., long-term vegetarian diet, extreme dieting) and no food allergies.
• Body weight fluctuation less than 3 kg in the past 6 months before enrollment.
• At least 20 natural teeth remaining in the oral cavity (excluding third molars).
• Able to understand and sign the written informed consent form voluntarily.
• Able to attend all scheduled follow-up visits as required.
• For participants in the interventional arm: diagnosed with periodontitis according to the 2018 International Classification of Periodontal and Peri-Implant Diseases and Conditions.

Exclusion Criteria:

• Systemic diseases such as diabetes mellitus, rheumatoid arthritis, or immunodeficiency disorders.
• Use of antibiotics, anti-inflammatory drugs, or antioxidant medications within 3 months before enrollment.
• Received any form of periodontal treatment (e.g., scaling, root planing, periodontal surgery) within 6 months before enrollment.
• Long-term use of medications known to affect gingival health, including calcium channel blockers, phenytoin, cyclosporine, or hormone replacement therapy drugs.
• History of smoking (current or former smokers) or use of tobacco products within the past 5 years.
• Pregnant or lactating women.
• Presence of severe oral mucosal diseases or active dental caries requiring immediate treatment.
• Participation in other interventional clinical trials within the past 30 days.
• Mental or cognitive disorders that may affect the ability to comply with study procedures.

Individual participant data (IPD) will not be shared with other researchers due to restrictions from the institutional review board (IRB) and hospital data management policies, which are designed to protect patient privacy and confidentiality. The aggregated results of this study will be published in peer-reviewed journals.