Surgical regenerative treatment of peri-implantitis lesions using a nanocrystalline hydroxyapatite or a natural bone mineral in combination with a collagen membrane: a four-year clinical follow-up report

Objectives The present case series aimed at investigating the 4-year clinical outcomes following surgical regenerative therapy of peri-implantitis lesions using either a nanocrystalline hydroxyapatite (NHA) or a natural bone mineral in combination with a collagen membrane (NBM+CM). Materials and Methods Twenty patients suffering from moderate peri-implantitis (n=20 intrabony defects) were randomly treated with (1) access flap surgery (AFS) and the application of NHA (n=9), or with AFS and the application of NBM+CM (n=11). Clinical and radiographic (R) parameters were recorded at baseline (R) and after 36 and 48 (R) months of non-submerged healing. Results One patient from the NBM+CM group was discontinued from the study due to severe pus formation at 36 months. Compared with NHA, the application of NBM+CM resulted in higher mean PD reductions (NBM+CM: 2.5 +/- 0.9 mm versus NHA: 1.1 +/- 0.3 mm) and clinical attachment-level gains (NBM+CM: 2.0 +/- 1.0 mm versus NHA: 0.6 +/- 0.5 mm) at 48 months. A radiographic bone fill was observed for five sites in the NHA group, and eight sites in the NBM+CM group. Conclusion While the application of NBM+CM resulted in clinical improvements over a period of 4 years, the long-term outcome obtained with NHA without barrier membrane must be considered as poor.