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 non-surgical therapY of patients with generalized aggressive periodontitis. Probing depth, clinical attachment level, gingival index and concentration of microorganisms and cytokines at baseline, 3, and 6 12 months after the procedure will be evaluated.

The study methodology is according to CONSORT-STATEMENT 2010 for randomized controlled clinical trials.

Study Design The study is designed as a prospective, interventional, parallel, blinded, randomized, controlled clinical trial of superiority.

Source of data The population of this study will be recruited among patients referred to the Science and Technology Institute - ICT- São José dos Campos, College of Dentistry. Patients will fill a healthy history questionnaire to ensure that they are medically qualified for participate in this study. Based on the power calculation for this study, a population of 38 patients will be included. Considering α of 5% and 10% β-type error (90% power) to detect a difference of at least 1 mm in probing depth reduction of pockets ≥ 5 mm between groups, for a standard deviation of 0.94 from a previous study evaluating different antimicrobials in the treatment of GAgP (Xajigeorgiou et al., 2006), 19 patients will be needed in each group.

Clinical Parameters All clinical parameters will be assessed by a single blinded, trained and calibrated examiner (CFA) before periodontal 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 (FMPI); 2) Bleeding on probing (BoP); 3) Probing depth (PD): distance from the bottom of sulcus/pocket to gingival margin; 4) Gingival recession (GM): 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, a total of ten patients presenting 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.

Treatment Protocols

All patients will be treated with periodontal therapy through of the one-stage, full mouth, ultrasonic debridement (FMUD). In a single session, patients will receive local anesthesia and periodontal debridement with ultrasound equipment (Cavitron - Dentsply EUA) and subgingival tips (UI25KSF10S, Hu-Friedy). All diseased sites will be instrumented in this one session. The debridement session will be performed by a single experienced and trained periodontist (NA), different from the examiner. Immediately before the mechanical therapy, patients will be allocated in one of the two treatment protocols:

Test group (n = 19): FMUD + 3 g of omega-3 polyunsaturated fatty acids and 100 mg of aspirin daily supplementation over a period of 180 days; Control group (n = 19): FMUD + placebo pills.

All patients will start taking the pills immediately before of the FMUD session.

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 GAgP (AAP, 1999);
• presence of ≥20 teeth;
• presence of ≥ 6 sites presenting PD ≥ 5mm with bleeding on probing (BOP) and ≥2 sites with PD ≥7mm (including incisors and first molars, in addition to other two non-contiguous teeth);
• good general health;
• agree to participate in the study and sign a written informed consent. All subjects will be individually informed about the objectives, probable risks and benefits of the protocol treatment (according to Resolution nº196 of October 1996 and to the Professional Code of Dental Ethics - 179/93).

Exclusion Criteria:

• pregnancy or lactating;
• suffer from any systemic disease (e.g. cardiovascular disorders, diabetes, blood dyscrasias, immunodeficiency, etc) which could alter the course of periodontal disease;
• took antimicrobials in the previous 6 months;
• taking long-term anti-inflammatory drugs;
• previous periodontal treatment within the last 12 months;
• smoker ≥ 10 cigarettes.