Objectives: The aim was to evaluate retrospectively the outcome of treatment with enamel matrix derivative (EMD) as adjunct to open flap debridement in periodontal intrabony defects, on the long-term (>15 years). Methods: All journals of patients in a public dental service specialist clinic treated with EMD (Straumann Emdogain®) as adjunct to open flap debridement in periodontal intrabony defects > 15 years ago were assessed for clinical and radiographic data. On digitized/digital bite-wing radiographs from prior to treatment (baseline), 1-year, and > 15 years after treatment, measurements of radiographic defect depth (RDD) defect width (RDW), and defect angle (RDA) were performed with ImageJ® and subjected to statistical analysis with the student’s t-test. Results: Twenty-two patients (11 female; mean age of 55±12 years) were identified. Out of 28 teeth treated 16-20 years ago, only one was lost; thus data from 27 available sites (22 patients) were available. Due to inconsistencies in the clinical registrations, only radiographic data were used. At baseline, PPD, CAL, RDD and RDW averaged 8.37±2.33mm, 9.33±2.19mm, 5.26±2.34mm and 2.33±0.77mm, respectively. After an average of 17 years from reconstructive EMD treatment, RDD and RDW were reduced by 2.84±3.50mm (p=0.0003) and 0.88±1.30mm (p=0.002), respectively comparing to baseline. Compared to 1 year after EMD treatment (RDD 1.90±1.31mm RDW 1.43±0.86mm ) no significant changes in RDD (-0.52±2.98mm, p=0.38) or RDW (-0.03±1.01mm, p=0.89) were observed 16-20 years after EMD treatment. Compared to baseline RDA (26.87±12.84°), no significant changes were observed 16-20 years after EMD treatment (25.14±19.21° p=0.66). Conclusions: The radiographic improvements, (i.e. defect depth and defect width reduction) achieved 1 year after treatment with EMD as an adjunct to open flap debridement in periodontal intrabony defects can be preserved over a period of 16-20 years.