PDLLA Screws for Fixation of Bone Grafts

"Objectives:" To determine the suitability of resorbable poly D.L.-lactid (PDLLA) screws for fixation of bone grafts without having negative influence on graft regeneration and osseointegration of dental implants. "Methods:" In 8 edentuluos patients suffering from insufficient retention of their upper denture related to severely resorbed maxilla, the floor of both maxillary sinus and width of the alveolar crest was augmented with an autologous bone graft from the iliac crest. Randomly, the bone graft used to augment the alveolar crest was fixed with 2 titanium screws on one side and 2 resorbable screws on the other side. Three months after reconstruction, a bone biopsy was taken with a trephine including 1 resorbable screw (n=8). Subsequently 6 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 histology. "Results:" Wound healing was uneventful. No difference in wound healing was observed between sides treated with either a resorbable or titanium screw. Six months after implantation, implant retained overdentures (follow up 22.2+4.3 months). Light microscopic examination at 3 and 9 months after reconstruction most of PDLLA material was still visible. The PDLLA screws were encapsulated by a layer of fibrous tissue containing many multinucleated giant cells (MGC). The MGC's were in direct contact with PDLLA screws as well as infiltrating in areas with fragmented PDLLA.Fragmentation of PDLLA with ingrowth of MGC was most pronounced 9 months after insertion of the screws. Around the screws no necrosis or hemorrhage was observed. The most Striking feature was the round/spherical form of polymer remnants of PDLLA material."Conclusions:" This study indicate that resorbable PDLLA screws can be used for fixation of bone grafts. The bulk of PDLLA material is still present after 9 months.