This is a 12-month longitudinal, double-blind, parallel-design randomized controlled clinical trial involving surgical therapeutic intervention (Phase 4). It will include 50 participants aged 21 diagnosed with periodontitis (Stage III/IV, Grade A or B), divided into a Test Group (n=25, Minimally invasive single-flap surgery) and a Control Group (n=25, Minimally invasive double-flap surgery). The objective of this randomized, double-blind clinical study is to compare clinical, radiographic, and patient-centered outcomes between minimally invasive single-flap and double-flap techniques in treating isolated infra-bony defects. Twenty-five patients will be treated using the single-flap approach, and 25 patients will receive the double-flap elevation technique. Clinical parameters (plaque and bleeding scores, probing depth, gingival recession, clinical attachment level, and papillary dimensions), digital measurements (changes in gingival margin and papillary volume), radiographic assessments, and patient-centered outcomes (VAS scale) will be evaluated immediately before surgery, at 6 and 12 months post-procedure, while early healing will be assessed after 1 and 2 weeks following the procedures. Mean values and standard deviations will be calculated for each variable, normal distribution will be tested using the Shapiro-Wilk test, and comparisons will be conducted using Student's t-test and one-way ANOVA. A significance level of 5% will be used for all analyses.

This is a clinical trial, a randomized controlled double-blind parallel-design study with a 12-month follow-up. Participants will be recruited from patients diagnosed with periodontitis (Stage III/IV, Grade A or B) based on inclusion and exclusion criteria at the Postgraduate Periodontics Clinic of the Dental College of Piracicaba in the State University of Campinas (FOP-UNICAMP). The sample size calculation was based on a previous study, resulting in 50 participants, with 25 in each group. Participants will be randomly assigned to two treatment groups: Control Group (double-flap minimally invasive surgery) and Test Group (single-flap minimally invasive surgery).

This study will include clinical, digital, radiographic and patient-related outcome measures parameters. Clinical parameters including plaque index, bleeding on probing, probing depth, gingival recession, clinical attachment level, and early healing index will be measured at baseline, 6 months, and 12 months. Digital parameters, including mean change in papillary volume (mmVP) and change in gingival margin (mGM), will be assessed through intraoral scanning at baseline and 12 months. Radiographic measurements (linear, angular, and subtraction) will be performed before surgery and 12 months after using specialized software. Patient perception of pain and analgesic consumption will be evaluated using the Visual Analogue Scale (VAS) at various time points post-surgery (1-14 days after surgical intervention).

The clinical protocol involves pre-surgical therapy, surgical therapy, and post-operative care. After recording all the parameters through periodontal evaluation, X-ray acquisition procedures and intraoral scanning, a full-mouth supra and subgingival scaling and root planing will be performed. Afterwards, the surgery will be performed, following the randomization. Patients will receive post-operative analgesics and instructions for oral hygiene modifications. Periodontal maintenance will occur at specific intervals after surgery (1 month after surgery, 2 months after surgery, 4 months after surgery, 7 months after surgery, 10 months after surgery and 12 months after surgery).

For the statistical analysis, descriptive statistics will be used, and normality will be tested. Comparisons will be made using Student's t-test, one-way ANOVA, or non-parametric tests if data do not follow a normal distribution. A significance level of 5% will be used for all analyses.

Inclusion Criteria:

• Systemically healthy individuals
• Diagnosis of periodontitis (stage III/IV - grade A or B)
• Presence of 20 or more teeth in the oral cavity
• Presence of at least one isolated interproximal infra-bony defect (without extension of the defect to the lingual or palatal area - assessed with preoperative bone sounding), with a probing depth of 6 mm or more, and a radiographic infra-bony component ≥ 4 mm, not associated with bifurcation areas, in anterior or premolar teeth (Schincaglia et al., 2015)
• Plaque index and bleeding on probing index ≤ 20% (baseline)
• Individuals providing informed and voluntary consent

Exclusion Criteria:

• Individuals who are not available for study evaluation appointments
• Systemic conditions that contraindicate periodontal surgery
• Patients requiring prophylactic antibiotics
• Compromised systemic condition (leukocyte dysfunction, bleeding disorders, neoplasms, uncontrolled metabolic or endocrine disorders, HIV infection)
• Individuals using bisphosphonates (oral or injectable use)
• Individuals using antibiotics and steroids (within 6 months prior to the study start)
• Illicit drug users
• Smokers
• Individuals with the tooth associated with the infra-bony defect having inadequate restoration, endodontic lesion, inadequate endodontic treatment, untreated carious lesions, and Grade III mobility
• Pregnant and lactating Women