48 adult patients participated in a single-centre randomized clinical trial with split- mouth design. They had presented at re-evaluation after initial non-surgical periodontal therapy (steps 1 and 2 of periodontal therapy) for generalized periodontitis with at least 2 teeth with residual probing pocket depths (PPD) ≥5 and ≤8 mm, with bleeding on probing (BOP). Two teeth with similar PPD were randomized to receive re-instrumentation either with (test) or without (control) adjunctive flapless administration of EMD. Differences in the changes of PPD and BOP from baseline to 6 and 12 months will be analysed, and the frequencies of pocket closure (PPD ≤4 mm and no BOP) will be compared

Inclusion Criteria:

• at least two residual pockets with probing pocket depth (PPD) ≥5 and ≤8 mm,
• bleeding on probing (BOP),
• mobility ≤degree 1 and
• no furcation involvement.

Exclusion Criteria:

• full mouth plaque score >20%,
• uncontrolled systemic disease,
• history of malignant disease in the oral cavity or previous radiotherapy in the head or neck area,
• pregnant or lactating females,
• drug and alcohol abuse,
• smoking >10 cigarettes per day and
• inadequate restorative therapy or malocclusion.