Resorbable screws for fixation of autologous bone grafts

The aim of this study was to evaluate the suitability of resorbable screws made of poly (D,L-lactide) acid (PDLLA) for fixation of autologous bone grafts related to graft regeneration and osseointegration of dental implants. In eight edentulous patients suffering from insufficient retention of their upper denture related to a severely resorbed maxilla, the floor of both maxillary sinus and width of the alveolar crest were augmented with an autologous bone graft from the iliac crest. Randomly, the bone graft used to augment the alveolar crest was fixed with two titanium screws on one side and two resorbable screws on the other side (split-mouth design). Three months after the reconstruction, a bone biopsy was taken with a trephine including one resorbable screw (N=8). Subsequently, six implants were placed in the left and right posterior maxilla. Six months later, at the abutment connection, a bone biopsy was taken including the other resorbable screw (N=8). The biopsies were processed for light microscopic examination. In addition, clinical parameters were scored. Wound healing was uneventful. Clinically no difference in wound healing was observed between sides treated with either a resorbable or titanium screw. No implants were lost. Six months after implantation, implant retained overdentures could be fabricated in all patients. All patients functioned well with their overdentures (follow-up 22.2 +/- 4.3 months). Three as well as 9 months after insertion (remnants of), the resorbable screws were still visible after reflecting the mucoperiosteum. Histological examination confirmed that a considerable quantity of remnants of the resorbable screws was still present, although areas with some fragmentation of the PDLLA were also observed. The screws were separated by a fibrous tissue layer containing many giant cells from the bone. Particles of PDLLA were observed within these giant cells. This study revealed that resorbable screws made of PDLLA can be used for fixation of bone grafts. The bulk of the PDLLA material is still present after 9 months.