Systemically healthy periodontitis patients were recruited in this single-blind, split-mouth, randomized controlled clinical trial. After SRP, PDT was applied at probing depth (PD) ≥ 4 mm at test quadrant. At baseline, 3rd month and 6th month, clinical parameters and cytokine pattern in gingival crevicular fluids (GCFs) were analysed.

Periodontal parameters and cytokine IL-1β, IL-6, IL-8, TNF-α, MMP-8 levels were analysed.

Inclusion Criteria:

• Adults who were medically fit or have medical condition that did not alter the outcome of periodontal treatment.
• Females who were not pregnant or nursing.
• Controlled diabetes mellitus with HbA1c < 7.5 mmol/L.
• Not on any antibiotics or steroids 3 months prior to periodontal treatment.
• Diagnosed to have either localized or generalized chronic or aggressive periodontitis (Armitage, 1999) with all 4 quadrants having at least 2 sites with probing depth ≥ 4 mm.
• Consented to follow the non-surgical periodontal treatment (scaling and root planing) with PDT throughout the period of study, i.e. approximately 6 months.

Exclusion Criteria:

• Allergic to photosensitizer or dye
• Pregnant lady and nursing mothers
• Uncontrolled diabetes

Allocation of test and control quadrants were done randomly by asking each study participant to choose either numbers "1" or "2". Number "1" defined quadrants 1 and 3 as the test quadrants while number "2" referred to quadrants 2 and 4 as the test quadrants. The remaining quadrants served as the control quadrants.