The aim of this randomized controlled clinical trial of superiority will be to evaluate the effect of 3 g of omega-3 polyunsaturated fatty acids and 100 mg of aspirin daily supplementation over a period of 180 days as adjunct to surgical therapy of residual pockets from patients with generalized aggressive periodontitis. Probing depth, clinical attachment level, gingival index and concentration of microorganisms and cytokines at baseline, 3, and 6 months after the procedure will be evaluated.

The study is designed as a prospective, interventional, parallel, blinded, randomized, controlled clinical trial clinical of superiority, with a 6 month follow-up. The methodology of the present study will follow the standards of CONSORT-STATEMENT 2010 (Moher et al., 2010) and SPIRIT 2013 (Chan et al., 2013) for randomized clinical trials.

Source of data The population will be composed of patients diagnosed with generalized aggressive periodontitis (GAgP) recruited at Institute of Science and Technology - Unesp, in São José dos Campos / SP, who have already undergone non-surgical periodontal treatment and still have pockets with probing depth ≥5 mm and bleeding on probe.

Sample size Sample size calculation was performed using Sealed EnvelopeTM software. For this study, a population of 34 patients will be included. Considering α = 5% and β = 5% (power of 95%) to detect a change of at least 1 mm in clinical attachment level between groups, to a standard deviation of 0.8 mm, 17 patients will be required in each group

Clinical Parameters All clinical parameters will be assessed by a single blinded, trained and calibrated examiner (CFA) before surgical therapy (baseline) and at 3 and 6 months after using a manual probe. Measurements will be done at six sites per tooth (mesiobuccal, buccal, disto-buccal, distolingual, lingual, and mesiolingual) in all teeth, except third molars.

The following clinical parameters will be evaluated: 1) Full-mouth plaque index (PI); 2) Bleeding on probing (BoP); 3) Probing depth (PD): distance from the bottom of sulcus/pocket to gingival margin; 4) Gingival recession (GR): distance from the free gingival margin to cement-enamel junction (CEJ); 5) Clinical attachment level (CAL): distance from bottom of sulcus/pocket to the CEJ. The CEJ will be identified by careful probe on cervical area.

Calibration and Randomization Initially, ten patients with GAgP will be selected. The designated examiner (CFA) will measure CAL and PD in all patients twice within 24 hours, with an interval of ≥ 1 hour between examinations. Then, the measures will be submitted to intraclass correlation test and the examiner will be judged calibrated if reaches 90% agreement.

Patients will be allocated into two groups according to a computer-generated list. The allocation will be implemented by an investigator (NC) who was not directly involved in the examination or treatment procedures.

Selection of sites with residual pockets

After the reevaluation, a residual periodontal pocket with probing depth ≥5 mm and bleeding on probe will be selected from a site not located in furcation region, by chance, to receive one of the following treatments:

• Control group (CG): surgical access for scaling and root planing + placebo pills (n = 17);
• Test group (TG): surgical access for scaling and root planing associated with daily supplementation of 3 g of omega-3 and 100 mg of acetylsalicylic acid for 180 days (n = 17).

Treatment

One hour before surgical therapy, patients will receive a single dose of dexamethasone 4 mg. The packaging of the products will be delivered according to the therapy indicated in the randomization. The administration will begin immediately before the surgical treatment, which will be performed by a single operator (CA), following the sequence:

1. 10 mL of 0.1% chlorhexidine digluconate solution (Periogard®, Colgate Palmolive Ltda - Osasco - SP) will be provided to be chewed by the patient for 1 minute for intraoral disinfection;
2. Antisepsis of the perioral region with sterile gauze soaked in chlorhexidine digluconate solution 0.2%;
3. The patient will receive local injectable anesthesia with mepivacaine 2% with epinephrine 1: 100,000 (Mepivacaína®, DFL - Rio de Janeiro / RJ) through an infiltrative technique;
4. Surgical access will be performed by Kirkland modified surgical technique (Kirland, 1931). With a 15c blade, intrasulcular incisions will be made to the bottom of the pocket / sulcus on buccal, lingual and interproximal surfaces. The incisions will extend into the mesial and distal directions of the affected tooth. The gingival tissue will be detached from the bone to allow exposure of the root surface which will be carefully scaled and plained with periodontal curettes after removal of all granulation tissue. After copious irrigation with saline solution, the flap will be repositioned and maintained by interproximal sutures with Ethicon ® 4-0 silk suture (Ethicon Johnsons do Brasil SA, São José dos Campos - SP).

Postoperative Patients will receive the following postoperative recommendations: do not drink alcoholic beverages; do not touch the surgical wound; Do not brush and floss area for 7 days; Ingest only cold liquid (ice cream, yogurt, juices and gelatin) in the first 24 hours; Mouthwash with 0.12% chlorhexidine digluconate (Periogard®) every 12 hours for 14 days. Dipyrone sodium 500 mg every 4 hours will be prescribed in case of pain. The sutures will be removed after 7 days of surgery.

Microbiological evaluation Subgingival microbiological samples will be collected at the baseline, 3 and 6 months after therapy. The site will be isolated with a sterile cotton roller and supragingival biofilm will be carefully removed with periodontal curettes and a sterile paper will be inserted into the periodontal pocket for 30 s (Hartoth et al., 1999). The sample will be stored in sterile microtubes. The samples will then be lyophilized and sent to the Department of Periodontology at the University of Florida, where the samples will be analyzed.

Evaluation of cytokines For the analysis of immunological changes, crevicular gingival fluid (CGF) will be collected at baseline, 3 and 6 months after treatment. Each site will be isolated with a sterile cotton roller and the supragingival biofilm will be removed. After this, the CGF will be collected with Periopaper strips (Periopaper, Oraflow, Plainview, NY, USA), inserted in the pocket for 15 seconds. The volume of collected fluid will be measured (Periotron 8000, Oraflow). The Periopaper strips will be stored in a sterile tube containing 300μl of phosphate saline (PBS) with 5% Tween-20 and stored in a freezer at -20 ° C until the multiplex test. The level of the following cytokines will be measured in the CGF: interferon (IFN) -γ, interleukins (IL) -10, -1β, -4, -6, -8, tumor necrosis factor (TNF) -α, macrophage inflammatory protein 1α (MIP1α), 1α monocyte chemotactic protein (MCP-1α). The 10-plex high sensitivity kit (Millipore Corporation, Billerica, MA, USA) will be used according to the manufacturer's instruction and analyzed using the MAGpixTM platform (MiraiBio, Alameda, CA, USA). Samples will be analyzed individually (each pocket separately) and the concentrations will be calculated using a standard 5-parameter curve in the Xponet program (Millipore Corporation). The concentration of each marker will be given in pg / ml. All analysis of cytokine concentrations will be done in duplicate.

Statistical analysis Two analyzes will be performed: Per Protocol and Intention-to-treat (Moher, 2010; Gupta, 2011; Day, 2008). For each of them, mean and standard deviation will be calculated in each of the parameters. Full-mouth PI, GI, PD, CAL, and GR will be submitted to the Shapiro-Wilk test to evaluate the distribution of these data, and then subjected to the variance test for both intra- and intra-group comparison. In addition, the number of pockets ≥ 5mm, the frequency of closure of these pockets, the mean reduction in PS and the gain in CAL of these pockets will be assessed before and after the therapy by performing intra- and inter-group analyzes.

The concentration of each cytokine will be analyzed by test of variance for intra and intergroup comparison.

Inclusion criteria

• Diagnosis of generalized aggressive periodontitis (Armitage, 1999; American Academy of Periodontology, 2015);
• Have undergone a first approach for periodontal treatment (full-mouth ultrasonic debridement);
• Present at least one residual pocket of probing depth ≥ 5 mm and bleeding on probe not located in furcation region;
• Good general health;
• Agree to participate in the study and sign the informed consent form (TCLE) after explaining the risks and benefits;

Exclusion Criteria

• Systemic problems (cardiovascular alterations, blood dyscrasias, immunodeficiency - ASA III / IV / V) that contraindicate the periodontal procedure;
• Have used antibiotics and anti-inflammatories in the last six months;
• Smoke ≥ 10 cigarettes/day;
• Pregnant or nursing;
• Chronic use of medications that may alter the response of periodontal tissues;
• Indication of antibiotic prophylaxis for dental procedures;
• History of allergic reaction to acetylsalicylic acid, fish or seafood.