The aims of the present study are to assess the significance of the adjunctive effect of the subgingival application of a 2% minocycline hydrochloride controlled-delivery system (MHS) in comparison to subgingival instrumentation with application of a placebo gel, 3 months after therapy in subjects with recurrent periodontitis undergoing supportive periodontal therapy (SPT) and to assess the substantivity of the gel attributable to the adjunctive delivery of the medication that is detected at 3 months during a 9-month period of regular SPT. Recurrent periodontitis will be defined as sites with residual periodontal probing depths and bleeding on probing after completion of initial periodontal therapy. This will include both persistent and recurrent periodontitis, where persistent means the residual periodontal site after initial periodontal therapy, and recurrent means the site which was improved by initial periodontal therapy, but disease recurred.

It has been reported that regular maintenance of subjects with treated periodontal disease is the key consideration in the long-term periodontal prognosis of these subjects. Periodic prophylaxis may prevent loss of clinical attachment over long periods of time even in patients with less than optimal plaque control. However, there are limitations in routine subgingival re-instrumentation especially in bleeding pockets, as only 50% of these sites improve. Furthermore, the persistence of bleeding pockets increases the risk of disease progression and tooth loss. Thus there is a need for adjuncts that may improve the outcome especially in subjects with recurrent periodontitis during SPT. Some studies reported significantly better results with subgingival administration of local minocycline in residual pockets post initial periodontal therapy over a short period of time. There are few studies assessing the efficacy of topical minocycline gel in subjects with recurrent periodontitis while in SPT, and the long term effect.

The present study will examine the significance of the adjunctive effect of the subgingival application of a 2% minocycline hydrochloride controlled-delivery system (MHS) in comparison to subgingival instrumentation with application of a placebo gel, 3 months after therapy in subjects with recurrent periodontitis undergoing supportive periodontal therapy (SPT) and to assess the substantivity of the gel attributable to the adjunctive delivery of the medication that will be detected at 3 months during a 9-month period of regular SPT.

Inclusion Criteria:

• Medically healthy adults (ASA classification I-II)
• At least 21 years of age.
• Previously diagnosed with moderate to severe periodontitis and had completed at least 1 round of periodontal therapy including scaling and root-planing, oral hygiene instructions.
• Treated periodontitis patients undergoing maintenance care for at least 6 months.
• Ability to comply with 12-month study follow-up.
• Recurrent moderate to severe periodontitis with no previous systemic antibiotic therapy during initial periodontal therapy.
• At least 4 teeth present with residual PPD of ≥ 5 mm on each and a positive bleeding on probing (BOP).

Exclusion Criteria:

• Medically compromised subjects (ASA classification III-V).
• Known allergy or other severe adverse reactions to minocycline and related drugs.
• Patients who reported local and/or systemic antibiotic therapy within 3 months prior to baseline examination of the study, and were placed on antibiotics during active initial periodontal therapy.
• Patients with a plaque control record > 30%.
• Patients who had history of surgical periodontal treatment less than 5 years in the area with lesions.
• Pregnant or intend to conceive or are breast feeding.

The examiners (PI and Outcomes Assessors) will be blinded during the clinical examination of the patients. The topical antibiotic will be administered by a trained and delegated clinician who is not involved in the outcome assessment.

Patients will be blinded to their treatment group as well.