Sponsorship was transferred as lead CI moved in 2019 and the trial was abandoned

This investigation aims to assess the clinical and radiographic outcomes of intrabony defects treated with minimally-invasive non-surgical therapy.

Periodontal diseases are inflammatory conditions that affect the supporting apparatus of the teeth, including gingiva and alveolar bone. The bone loss resulting from periodontitis often is irregular and localised, giving onset to 'intrabony' or 'vertical defects' affecting one side of the tooth more than the other and more than on the neighbouring teeth. Periodontal intrabony defects have been associated with a higher risk of further progression and eventually tooth loss.

The treatment of periodontitis involves a non-specific reduction of the bacterial load below the gingival margin. This is achieved by oral hygiene instructions (OHI) and non-surgical periodontal therapy (NSPT), aimed at removing calculus and disrupting the plaque biofilm from the affected root surfaces. Intrabony defects are considered sites requiring therapy, often beyond NSPT. Decades ago, intrabony defects were treated with surgical elimination of the defect achieved by sacrificing the adjacent healthy supportive or non-supportive bone. More recently periodontal regenerative procedures have been advocated for deep intrabony defects, which are considered amenable for guided tissue regeneration. This technique results in regeneration of periodontal attachment measurable histologically and radiographically and measurable clinically. However, this is associated with potential morbidity and high costs due to the use of bone graft and barrier materials and is not always predictable. The more recent introduction of minimally-invasive surgical therapy (MIST), modified-MIST (M-MIST) and single-flap approach suggested that the use of biomaterials may not be so crucial for obtaining periodontal regeneration.

A retrospective study from our group has shown that non-surgical periodontal treatment of intrabony defects results in clinical improvements (measured as PPD reductions and clinical attachment level-CAL- gain) but also in bone fill of the bony defects, measurable radiographically. The extent of the radiographic resolution of the defect was positively associated with initial defect depth and use of adjunctive antibiotics, while smoking seemed to negatively influence this outcome. A non-surgical minimally-invasive treatment protocol, named MINST, has been proposed along these principles. A more recent retrospective analysis has revealed a reduction in bony defect of nearly 3 mm for cases treated with minimally-invasive non-surgical therapy. The effect of MINST may be mediated by improved blood flow and stable blood clot in the intrabony defect. However, very few studies have been published on MINST and no data are available on generalizability and wide applicability of MINST.

This is a prospective cohort multicentre study to assess the effect of a modified minimally-invasive non-surgical therapy (MINST) approach in the healing of 100 periodontal intrabony defects in patients with periodontitis seen in private practice. The therapists responsible for delivering this treatment as part of this study all have experience in routinely carrying out this or similar procedures for this type of periodontal defects.

Inclusion Criteria:

1. Age 18-70
2. Diagnosis of Periodontitis (Tonetti et al. 2018)
3. Presence of ≥1 'intrabony defect' (PPD and CAL >5 mm with radiographic intrabony defect depth ≥3mm and not in a site associated with furcation involvement)
4. Signed informed consent [Participants must be able and willing to read and sign a copy of the "Informed Consent Form" (ICF) form after reading the "Patient Information Leaflet" (PIS), and after the nature of the study has been fully explained].

Exclusion Criteria:

1. Smoking (current or in past 5 years, including electronic cigarettes, vaping or similar)
2. Medical history including diabetes or hepatic or renal disease, or other serious medical conditions or transmittable diseases
3. Presence of drug-induced gingival enlargement
4. History of conditions requiring prophylactic antibiotic coverage prior to invasive dental procedures
5. Anti-inflammatory or anticoagulant therapy during the month preceding the baseline exam
6. Systemic antibiotic therapy during the 3 months preceding the baseline exam,
7. Taking immunosuppressant medications
8. Known allergy to local anaesthetic
9. History of alcohol or drug abuse
10. Self-reported pregnancy or lactation
11. Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that according to the investigator may increase the risk associated with trial participation
12. Periodontal treatment to the study site within the last 12 months (excluding not-extensive subgingival debridement as judged by the examining clinician).