Spontaneous progression of experimental peri-implantitis in augmented and pristine bone: A pre-clinical in vivo study

Objective: To examine the progression of experimental peri-implantitis around different implants placed in augmented and pristine sites.

Materials and methods: Six labrador dogs were used. Three months after tooth extraction, four implants with different surface modifications were installed on each side of the mandible. A standard osteotomy was applied on one side, while on the contralateral side the osteotomy was modified, resulting in a gap between the implant and the bone wall. The gap was filled with a bone substitute and covered by a resorbable membrane. Three months after implant installation, implants were exposed and healing abutments were connected. Two months later, oral hygiene procedures were abandoned and a cotton ligature was placed in a submarginal position around the neck of all implants and kept in place for 4 weeks. Following ligature removal, plaque formation continued for 6 months (spontaneous progression period). Radiographs were obtained throughout the experiment, and biopsies were collected and prepared for histological evaluation at the end of the spontaneous progression period.

Results: Differences in bone loss during the spontaneous progression period between pristine and augmented sites were small. The size and vertical dimension of the peri-implantitis lesion were larger at augmented than at pristine sites. Implants with non-modified surfaces exhibited smaller amounts of bone loss and smaller dimensions of peri-implantitis lesions than implants with modified surfaces.

Conclusion: Small differences in spontaneous progression of peri-implantitis were detected between pristine and augmented sites. Implants with modified surfaces exhibited more bone loss and larger lesions than implants with non-modified surfaces, irrespective of the type of surrounding bone.