K. Puumanen1, M. Kellomäki2, V. Ritsilä3, T. Böhling4, P. Törmälä2, T. Waris5

Department of Surgery1, Malmi Hospital, Helsinki;
Institute of Biomaterials2, Tampere University of Technology, Tampere;
ORTON Research Institute3, The Invalid Foundation of Helsinki, Helsinki;
Department of Pathology4, Hartman Institute, University of Helsinki;
Department of Plastic Surgery5, Oulu University Central Hospital, Oulu, Finland.

Introduction: The tendency of bone grafts to undergo resorption is a problem in maxillary cleft surgery in children. An experimental model of maxillary cleft deformity and operative technique using biodegradable materials was designed. The aims of the study were to investigate the possible ability of biodegradable materials to protect bone grafts from resorption and to promote and guide bone formation.

Material and methods: Poly-L/D-lactic acid (P(L/D)LA 96/4) as a thin mesh and a composite membrane consisting of a film made of copolymer of L-lactic acid and caprolactone (P(L-LA/e-CL)) 50/50) combined with P(L/D)LA 96/4 mesh were used. Thirty New Zealand White rabbits 8 to 9 weeks old were operated on. A standard maxillary alveolar 6 x 6 mm defect was created on both sides of the maxilla. Autogenous bone grafts were used to fill in all the defects and a biodegradable material was placed over the defect and under the periosteum on one side, the other side served as a control receiving the bone graft only. Three groups were formed: 1) defect covered with mesh vs. control defect, 2) defect covered with composite membrane vs. control defect and 3) defect covered with mesh on one side and with composite membrane on the other side. X-rays were taken immediately after the operation, at 3 and 6 weeks and at the end of the follow-up period of 10 weeks. Fluorochrome- labelling with oxytetracycline was done at 4 and 6 weeks postoperatively. Samples were taken for histological and histomorphometric evaluation.

Results: After preliminary radiological evaluation the biodegradable composite membrane appears to promote healing of the bone defect when compared with the mesh and healing of the control defect. The preliminary results of histological and histomorphometric analyses will be presented.

Conclusions: Preliminary results indicate that a biodegradable composite membrane of poly(L/D-) lactide (96/4) mesh and (L-) lactide/ (e-) caprolactone (50/50) copolymer film may promote bone formation and prevent bone resorption in an experimental maxillary alveolar cleft model in growing rabbits.