Timing of Success Evaluation After Flapless Treatment of Peri-Implantitis

• Flapless non-surgical treatment of peri-implantitis (Procedure): Non-surgical flapless treatment consisting of oral hygiene motivation and instructions, removal of the implant-supported prosthesis when possible, modification of the emergence profile when indicated, supra- and submucosal mechanical debridement using ultrasonic devices with periodontal tips and steel curettes, removal of granulation tissue, and curettage of the peri-implant mucosa. Followed by chlorhexidine gel twice daily for 15 days and systemic antibiotic therapy (metronidazole 500 mg three times daily for 7 days, or azithromycin 500 mg once daily for 3 days in case of allergy/contraindication)

Primary outcomes

• Clinical Success Following Flapless Treatment of Peri-Implantitis [6 weeks, 12 weeks, 6 months, 9 months, and 12 months after treatment]: Clinical success, recorded dichotomously (success/no success), assessed at six sites per implant. An implant is classified as a clinical success when probing depth (PD) is ≤5 mm at all six sites, bleeding on probing is present at, at most, one site and presents as an isolated spot rather than a line or profuse bleeding, and suppuration is absent at all sites.

Secondary outcomes

• Age (Years) [Baseline (T0)]: Age at inclusion, recorded in completed years.
• Sex (Male/Female) [Baseline (T0)]: Sex of participants.
• Smoking Status (Never Smoker/Former Smoker/Current Smoker) [Baseline (T0)]: Smoking status classified as never smoker, former smoker, or current smoker. In current and former smokers, cumulative smoking exposure will be recorded in pack-years; in current smokers, daily cigarette consumption will also be recorded.
• Periodontal Diagnosis (Stage I-IV; Grade A-C) [Baseline (T0)]: Periodontal diagnosis according to the classification of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.
• Arch (Maxilla/Mandible) [Baseline (T0)]: Location of the implant by dental arch.
• Location (Anterior/Premolar/Molar) [Baseline (T0)]: Implant location within the arch.
• Implant Type (Bone Level/Tissue Level) [Baseline (T0)]: Type of implant according to its design.
• Implant Length and Diameter (mm) [Baseline (T0)]: Implant length and diameter, recorded in millimeters.
• Surface Type (Machined/Rough) [Baseline (T0)]: Implant surface type.
• Implant-Abutment Connection Type (Internal/External) [Baseline (T0)]: Type of connection between implant and abutment.
• Time in Function (Years) [Baseline (T0)]: Time elapsed since implant placement, recorded in years.
• Prosthesis Type (Single-Unit/Partial/Multiple) [Baseline (T0)]: Type of implant-supported prosthesis.
• Intermediate Abutment (Yes/No) [Baseline (T0)]: Presence of an intermediate abutment.
• Prosthetic Modification During Treatment (Yes/No) [Flapless treatment visit (T-treatment)]: Whether a prosthetic modification was performed during the flapless treatment visit.
• Modified Plaque Index (0-3) [Baseline (T0), and at 6 and 12 weeks, and 6, 9, and 12 months (T1-T5)]: Presence of plaque, recorded at six sites per implant using the modified plaque index (Mombelli et al., 1987).
• Probing Depth (mm) [Baseline (T0), and at 6 and 12 weeks, and 6, 9, and 12 months (T1-T5)]: Distance, in millimeters, from the mucosal margin to the base of the peri-implant pocket, measured without the prosthesis in place, recorded at six sites per implant using a PCP-UNC 15 periodontal probe.
• Bleeding on Probing (Present/Absent) [Baseline (T0), and at 6 and 12 weeks, and 6, 9, and 12 months (T1-T5)]: Presence or absence of bleeding on probing, recorded at six sites per implant.
• Suppuration on Probing (Present/Absent) [Baseline (T0), and at 6 and 12 weeks, and 6, 9, and 12 months (T1-T5)]: Presence or absence of suppuration on probing, recorded at six sites per implant.
• Implant-Mucosa Distance (mm) [Flapless treatment visit (T-treatment)]: Distance between the mucosal margin and the implant shoulder, measured after prosthesis removal at six sites per implant. Recorded as positive when the mucosal margin is apical to the implant shoulder, and negative when coronal to it.
• Keratinized Mucosa (mm) [Flapless treatment visit (T-treatment)]: Distance between the mucosal margin and the mucogingival junction, measured at six sites per implant.
• Retreatment Performed (Yes/No) [12 weeks, and 6, 9, and 12 months (T2-T5)]: Whether retreatment (re-instrumentation without adjunctive systemic antibiotics) was performed, and timing.
• Need for Surgical Peri-Implant Treatment (Yes/No) [12 weeks, and 6, 9, and 12 months (T2-T5)]: Whether additional surgical peri-implant treatment was required, and timing.
• Implant Loss (Yes/No) [12 weeks, and 6, 9, and 12 months (T2-T5)]: Whether the implant was lost/extracted, and timing.
• Radiographic Defect Morphology (Supracrestal/Intrabony/Combined) [Baseline (T0)]: Morphology of the radiographic bone defect, classified as supracrestal, intrabony, or combined, assessed on periapical radiographs obtained using the long-cone paralleling technique and analyzed with ImageJ® software after calibration using the known implant length.
• Radiographic Bone Level (mm) [Baseline (T0), and at 6 and 12 months (T3, T5), or at any other visit if clinically necessary]: Distance, in millimeters, between the implant shoulder and the base of the bone defect, assessed on periapical radiographs obtained using the long-cone paralleling technique and analyzed with ImageJ® software after calibration using the known implant length.
• Intrabony Defect Depth (mm) [Baseline (T0)]: Depth of the intrabony component of the radiographic defect, assessed on periapical radiographs.
• Intrabony Defect Width (mm) [Baseline (T0)]: Width of the intrabony component of the radiographic defect, assessed on periapical radiographs.
• Intrabony Defect Angle (º) [Baseline (T0)]: Angle of the intrabony component of the radiographic defect, assessed on periapical radiographs.
• Treatment Trajectory (Success Without Retreatment/Success After Retreatment/Persistent Failure at 12 Months/Surgical Treatment or Implant Loss) [12 months (T5)]: Implant status at the 12-month outcome, classified as: success without retreatment; success after retreatment; persistent failure at 12 months; or surgical treatment/implant loss. An implant is considered a treatment failure if classified as either persistent failure at 12 months or surgical treatment/implant loss.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Patients aged 18 years or older.
* General health status compatible with dental treatment (ASA I-II).
* Ability to understand the study, sign the informed consent form, and comply with the follow-up protocol.
* Presence of one or more dental implants in function for at least 12 months, placed at any center, regardless of connection type or the presence of platform switching.
* Screw-retained implant-supported prostheses (single-unit, partial, or complete).
* Presence of at least one implant diagnosed with peri-implantitis, according to the criteria of the 2017 Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

Exclusion Criteria:

* Refusal to participate in the study or inability to provide informed consent.
* Non-acceptance of the proposed treatment.
* Pregnancy or breastfeeding.
* Treatment with drugs or presence of diseases that may alter the healing of peri-implant tissues or interfere with the response to treatment (e.g., immunosuppressants, systemic corticosteroids at immunosuppressive doses, or treatment with antiresorptive or antiangiogenic agents).
* Implants restored with cemented prostheses.
* Implants with mobility or with radiographic bone loss exceeding 50%.
* Surgical or non-surgical peri-implant treatment of the affected implant within the previous 12 months.
* Systemic antibiotic treatment within the previous 3 months.