The objective of this study is to determine whether, in patients with non treated periodontitis (stage III and IV) positive to Porphyromonas gingivalis, the use of systemic antimicrobials (metronidazole versus azithromycin) as an adjunctive treatment to periodontal surgery provides clinical and microbiological benefits.

Design: randomized, parallel and triple blind clinical trial

Sample: Patients with periodontitis (stages III and IV) and positive to Porphyromonas gingivalis who potentially need periodontal surgery were recruited. 25 patients were randomized to the test group (periodontal surgery + azithromycin) and another 25 subjects to the control group (periodontal surgery + metronidazole).

Study visits:

• Examiner calibration

• Recruitment of patients. Screening. Data collection (clinical and microbiological variables).

• Phase I.

  • Non-surgical periodontal treatment (2 visits).
  • Reevaluation at 6 weeks. Data collection (clinical and microbiological variables). Identification of study candidate patients (Patients with probing pocket depth > 5 mm and positive to Porphyromonas gingivalis). Randomization of study groups.

• Phase II. Surgical periodontal treatment.

  • Periodontal surgery sessions. In the last surgery, the antibiotic test (azithromycin) or metronidazole (control) is administered according to randomization.
  • Suture removal 1 week after performing periodontal surgery. Data collection 1 week after antibiotic consumption with the last surgery (patient-centered variables on the side effects of antibiotics).
  • Re-evaluation of the surgical phase at 6 weeks after the last surgery session. Data collection (clinical variables).

• Phase III. Periodontal maintenance.

  • Maintenance 1 (3 months post surgery). Data collection (Clinical and microbiological variables).
  • Maintenance 2 (6 months post surgery). Data collection (Clinical and microbiological variables).
  • Maintenance 3 (9 months post surgery). Data collection (Clinical variables).
  • Maintenance 4 (12 months post surgery). Data collection (Clinical and microbiological variables).
  • Maintenance 5 (4 years post surgery). Data collection (Clinical and microbiological variables).

Inclusion Criteria:

• Diagnosis of periodontitis (stages III or IV) that may require periodontal surgery
• Have at least 10 teeth in function, excluding third molars.
• Present locations with probing depth (PS)> 6 mm in at least 30% of the teeth.
• Present radiographic evidence of moderate-severe bone loss in at least 30% of the dentition.
• Detection of P. gingivalis in subgingival samples taken at the screening visit as well as in the post-scaling and root planning visit and processed by culture.
• Systemically healthy patients.

Exclusion Criteria:

• Pregnant or lactating women.
• Presenting systemic pathology and / or taking medication that may affect the periodontal situation and / or patients requiring antibiotic prophylaxis.
• Have received systemic antimicrobial treatment in the previous 6 months.
• Have received periodontal treatment in the 6 months prior to the beginning of the study.
• Patients allergic to metronidazole, or to any of the components of commercial formulations thereof (Flagyl®).
• Patients allergic to azithromycin, or to any of the components of commercial formulations thereof (Zithromax®).
• Patients who refuse to sign the informed consent.

The subjects were randomly assigned to the treatment groups in ascending order according to a balanced distribution system through a computer generated random number design table (random block design). Randomization was balanced according to the smoking habit at the initial visit to ensure homogeneity in the treatment groups.

The method of allocation concealment selected were opaque envelopes. The research coordinator was responsible for the randomization and allocation of patients.

The 50 opaque envelopes (25 / group) were prepared.