REGENERATION OF BONE AFTER PLACMENT OF ?CO-POLYMER OF L-D POLYLACTIC AND POLY GLYCOLIC ACIDS IN SURGICALLY CREATED DEFECTS

This experimental study was conducted on twelve mongrels dogs, standard critical size defects were surgically created in both sides of the mandible of all of the animals. The right side defects were obliterated by a mixture of gel type and powder type Fisiograft which is a copolymer of Polylactic and Polyglycolic acids. While the left side defects were left empty to act as controls. At each interval of one, three, six and nine months postoperative , the dogs were sacrificed and the test and control defects were compared histologically. 1) The histological examination after one month revealed that in both the test and control defects, masses of granulation tissue invaded the created defects, few osteoid tissue appeared only in the base of the defect in the control defects. On the other hand, much more osteoid tissue appeared along the periphery of the test side defect and few of them were scattered in the center of the defect. 2) After three months, the new formed bone creped along the periphery of the test side defect, became homogenous and showed continuity with the normal bone , while in the control defect, it was still accentuated in the base of the defect , separated by fibrous tissue from normal bone and composed of heterogeneous masses. 3) The specimens of the sixth month showed condensation of the haversian systems of both defects, but those of the test side were more homogenous and mature. 4) After nine months, there was marked maturation of the new bone formed in the control side, while the rate of maturation of the test side was markedly slowed down, wide bone marrow spaces and poor haversian systems were demonstrated in both defects, however, the bone quality of the test side defects was ahead of that of the control side defects, as narrower bone marrow spaces and more mature haversian systems were demonstrated in the test side defects.