The sample consists of patients with moderate to severe periodontitis who will be subjected to machanical therapy in combination to local antibiotics. The participants will be divided into two groups, mechanical therapy with metronidazole hyclate, and mechanical therapy with minocycline hydrochloride. Both antibiotics will be delivered locally as gels. Outcome measures include probing pocket depth and several gingival indices. IL6 will be also measured for all participants.

Forty-four patients in the age group of 25-50 years (males and females) who are suffering from periodontitis with almost similar probing depth bilaterally (≥ 6 mm) at the selected sites and exhibiting bleeding on probing.

A written informed consent will be taken from the patients prior to the study.

Each patient will be recalled 4 weeks after completion of both sides supra-gingival scaling, which formed the baseline visit. Plaque scores will be brought to zero, and the probing pocket depth and gingival index, will be recorded on the proforma specially prepared for the purpose.

The selected treatment sites will be then divided into two groups, and sub-gingival SRP will be performed prior to the delivery of the drugs at the test sites.

• Group I: Consist of periodontal pockets on the left side of maxillary or mandibular arch and received sub-gingival Minocycline 2% gel.
• Group II: Consist of periodontal pockets on the left side of maxillary or mandibular arch and received Metronidazole 0.75% gel.

The right side will be left as a control in both groups Patients will be recalled after 6 weeks from the baseline visit to record the plaque index, gingival index, bleeding index and probing depth (UNC probe 12 mm).

Statistical Analysis:

The unit of measurement in this study is the site, rather than the subject. Student-t test was To compare between Group 1 (Minocycline 2 %) and Group 2 (Metronidazole 0.75 %), Data will check for normality, if the data normally distributed Independent t-test will use to test if there any significant differences between groups, otherwise if not normally Mann -Whitney U-test (Non-parametric) will use to detects the difference.

To achieve 80% power of statistical test to detect the differences between Metronidazole and Minocycline With 5 % level of significant, 19.6 reduction in probing depth (previous study-vi) and standard deviation of 0.23, using the following formula.

n=(2σ^2 〖(Z_(β+Z_(1-α/2) ))〗^2)/d^2 22 per group (minimum sample size) where: σ =0.23 Zβ =0.84 Z(1-α/2) =1.96, d= 19.6%

For objective 2, the statistical test in case of normal data distribution will be paired t test or will use Willcoxon Sign Ranked test if it not normally distributed.

To achieve 80% power of statistical test to detect the differences between Metronidazole and Minocycline. With 5% level of significant.

Inclusion Criteria:

• Patients suffering from chronic periodontitis with almost similar probing depth bilaterally (≥
• 6 mm) at the selected sites and exhibiting bleeding on probing Patients with no caries and restorations on the selected teeth
• Patients showing effective individual oral hygiene.

Exclusion Criteria:

Patients presenting with history of intake of local and/or systemic antibiotic therapy for the last 3 months

• Patients with known systemic and debilitating diseases (Muscular Dystrophy)
• Patients presenting with known adverse reactions to any component of the test agent
• Patients on anticoagulant therapy
• Pregnant and lactating females
• Smokers
• Patients in a regular use of mouth wash

Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)