The aim of the study is to evaluate the effectiveness of Hypochlorous Acid and Chlorhexidine as postsurgical antimicrobial agents in the treatment of severe chronic periodontal disease. The selected patients will be randomly divided into two groups of 16 each. Subjects in group I will undergo scaling and surgical root planing and will use mouthrinse with 0.05% HOCl for 7 days, after this they will mouthwash with 0.025% HOCl until day 21 and Subjects in group II will undergo scaling and surgical root planing followed by a rinse with CHX 0.2% for 7 days, after this they will mouthwash with 0.12% CHX until day 21. Null Hypothesis: There are no significant differences between hypochlorous acid and chlorhexidine in reducing plaque formation at 7, 21 and 90 days of evaluation.

There are no significant differences between HOCl and CHX in the elimination or reduction of periodontopathogenic microorganisms at 7, 21 and 90 days. Alternative hypotheses: There are significant differences between hypochlorous acid and chlorhexidine in reducing plaque formation at 7, 21 and 90 days of evaluation. There are significant differences between HOCl and CHX in the elimination or reduction of periodontopathogenic microorganisms at 7, 21 and 90 days.

For the HOCl effectiveness study, parallel groups were compared to determine the clinical and microbiological effectiveness of hypochlorous acid by evaluating the reduction of plaque index, gingival index and clinical insertion level as a primary outcome with chlorhexidine, for a period of 7, 21 and 90 days. The selected patients will be randomly divided into two groups of 16 each. Subjects in group I: 16 subjects for scaling and surgical root planing (surgical technique Modified Widman) and HOCl 0.05% for 7 days and HOCl 0.025% until day 21 and Subjects in group II: 16 subjects for scaling and surgical root planing (surgical technique Modified Widman) and CHX 0.2% for 7 days and 0.12% CHX until day 21. At the beginning of the study (day0) all patients will be evaluated the plaque index, gingival index, periodontal chart, saliva sample collection and subgingival microbiological test, all will receive surgical periodontal treatment (scaling and surgical root planing surgical technique Modified Widman) after the surgery will be instructed to rinse with 15 ml twice a day for 30 seconds in the morning 30 minutes after breakfast and brushing teeth, and at night, before going to sleep with one of the two Rinses: HOCl 0.05% for the first seven days and 0.025% from day eight to day 21 and CHX 0.2% for the first seven days and 0.12% from day eight to day 21. The rinses were coded to avoid any bias and the codes will not be broken before the study ends. Patients will be assigned randomly each will receive a flushing flask identified as solution "A" or "B". These bottles will be identical in terms of shape, color and material. Neither the subject nor the dentists will be informed about the group assignment. The principal investigator who does not participate in the treatment or data collection will have access to a closed envelope with the allocation information. Each of the participants will be clear that the area where the surgical procedure should be performed should remain unbrushed for 21 days. After 21 days all individuals will be given a special toothbrush for after surgery and indications are given for the brushing of the operated area. Adverse effects were evaluated both microbiologically to verify the absence or presence of opportunistic flora associated with the use of mouthwashes and effects on teeth and mucous membranes using a survey and clinical assessment.

The data will be collected as follows:

Day zero will evaluate plaque and gingival index, periodontal pocket depth al probing, clinical insertion level, saliva uptake and subgingival sampling for microbiological analysis. On day 7 suture removal and plaque and gingival index, saliva sampling and subgingival sampling for microbiological analysis were evaluated. On day 21, plaque and gingival index, saliva sampling and subgingival sampling will be evaluated for microbiological analysis. And on day 90, plaque and gingival index, periodontal pocket depth at probing, clinical insertion level, saliva sampling and subgingival sampling for microbiological analysis.

For the test the following parameters will be evaluated: Gingival Index and Plaque Index. The modified gingival index and the modified visible plaque index will be evaluated. Four evaluations will be performed: one at the beginning of the study, another at day 7, 21 and the last at day 90 and the Index of visible plaque and Gingival index (Modified Silness & Loe) will be used. The probing depth and the level of clinical insertion will be measured in six sites per tooth (mesiobuccal, buccal, distobuccal, distolingual, lingual and mesiolingual) exclusion of the third molar, on day 0 and 90. Measurements will be recorded in the periodontal chart and a North Carolina periodontal probe (Hu-Friedy, Chicago, IL, USA) will be used. Sampling of saliva and microbial count: Microbiological samples in saliva and subgingival will be collected before surgery (day 0) and after surgery at day 7, 21 and 90. For the sampling of subgingival bacteria, the selected sites were cleaned (sterile curettes) before sampling, with cotton roll the field is isolated and dried carefully to avoid contamination, bacterial samples will be collected with paper tips of endodontics sterile (size 55 absorbent paper, Dentsply, Maillefer). Samples will be individually placed in labeled Eppendorf tubes containing Buffer, kept at -70°C and then sent to the laboratory. Will be processed in the laboratory of Oral Microbiology of the Universidad el Bosque. Samples will be analyzed using the real-time PCR technique.

Inclusion Criteria:

• Men and women.
• Age between 20 and 60 years.
• Diagnosis of chronic periodontitis.
• Minimum 20 teeth and minimum 3 teeth with at least one site with PD≥5 mm and CAL> 4 mm
• Radiographic evidence of bone loss.
• Good general health.

Exclusion Criteria:

• Prior periodontal therapy.
• Smokers.
• Antibiotic therapy in the last 4 months, consumption of NSAIDs.
• Pregnancy and / or breastfeeding.
• Systemic pathology that may affect the progression of PD.
• Allergy to HOCl or CHX.

The rinses will be coded to avoid any bias and the codes will not be broken before the study ends. Patients will be randomly assigned to receive a rinse bottle identified as solution "A" or "B". These bottles will be identical in terms of shape, color and material. Neither the subject nor the dentists will be informed about the group assignment. The principal investigator who does not participate in the treatment or data collection will have access to a closed envelope with the allocation information.