Effect of a bioresorbable film on regeneration of cranial bone.

Regeneration of cranial bone is usually accomplished with autografts, banked bone, or both. The effect also may be obtained by using a properly engineered alloplastic barrier. Our group assessed histomorphometrically the capacity of a bioresorbable film to promote repair of cranial bone in critical-sized defects in 50 rabbits divided over four time periods (4, 8, 16, and 24 weeks). A single circular defect 15 mm in diameter was prepared in each rabbit and either covered with films of polylactic acid (21 mm in diameter, 150 microns thick) durally and pericranially or left untreated. Only after 24 weeks was there a significant difference (p < or = 0.05) between defects covered with polylactic acid films and those untreated. We conclude that after shorter periods, regardless of covering, prolapse of soft tissue into defects prevented osseous regeneration. We speculate that at 24 weeks, defects treated with films generated new bone as a result of changes in the local milieu conducive to osteoblastic expression.