TREATMENT OF EXPOSED IMPLANT THREADS USING A SYNTHETIC BONE-GRAFT

The aim of this study was to evaluate clinically and histologically the use of a synthetic bone graft (Ionogran(R)) alone and in combination with guided bone regeneration (GBR) to facilitate bone regeneration and augmentation around exposed implant threads. Five male Beagle dogs were used in this investigation, Prior to the study all 3rd and 4th premolars were extracted. After 3 months, a flap was elevated and two Branemark implants were inserted in each quadrant in such a way that two-three threads remained exposed over the alveolar bone. On the control sites the synthetic bone graft was then placed around the exposed threads and the flaps were repositioned and sutured. On the test sites, the same procedure was performed, but an expanded polytetrafluoroethylene barrier was placed to cover the bone graft and implants. Three months after implant placement, the barriers on the test sites were removed, healing abutments were inserted on al implants, and a thrice weekly plaque control regime was initiated. The following clinical parameters were measured at 1, 2 and 3 months: Plaque Index, Gingival Index, Probing Depth and Clinical Attachment Level. Three months after abutment connection the animals were killed and specimens were obtained for histological evaluation. Clinical parameters revealed a significant improvement on the experimental sites compared to control sites during the month loading phase. Histological analyses, however, could not determine a difference in the nature of the implant/tissue interphase between experimental and control sites. In both groups graft particles were surrounded by dense fibrous connective tissue with limited evidence of new bone formation or osseointegration only in areas close to the alveolar crest.