AIM:
The aim of this study was to assess the stability over time of periodontal intrabony defects treated with minimally invasive non-surgical therapy (MINST) and supportive periodontal therapy (SPT).

METHODS:
Clinical and radiographic analysis was carried out in 21 intrabony defects treated with MINST in 14 consecutive patients included in a prospective study and reassessed after 5 years of SPT. Baseline, 1- and 5-year radiographs were analysed, and bone levels were compared by multilevel linear regression adjusted by latent variable method.

RESULTS:
None of the 21 teeth with intrabony defects was lost at 5 years. Average probing pocket depth, clinical attachment level and radiographic intrabony vertical defect depth reductions were 3.6, 3.5 and 2.6 mm, respectively, 5 years after treatment (p < 0.001 compared with baseline). Further non-statistically significant reductions were seen in clinical and radiographic measures between 1 and 5 years. Deeper initial defects and narrower angles were predictive of a bigger reduction in defect depth (p < 0.001 and p = 0.017, respectively).

CONCLUSIONS:
Clinical and radiographic improvements in intrabony defects after MINST seen at 1 year are stable up to 5 years, bringing evidence to support its long-term efficacy for the treatment of intrabony defects in non-smokers.