ABSTRACT
Twenty-four guinea pigs were divided into three major groups: Group I was the control group, in group II animals were given bleomycin [1.42 mg/kg, i.m.] and in group III animals were given methotrexate [4.725 mg/kg, i.m.]. The animals were sacrificed at 1, 2, 4 and 6 weeks postoperatively. The left lower incisor was extracted under ether anesthesia, one day after injection of the cytotoxic agent or saline. H and E-stained sections were examined. Histologically, bleomycin reduced collagen formation, which is reflected in reduced wound breaking strength in the first phase of healing, retarded wound healing in the second phase of healing, but had little or no effect in the third phase of healing. Methotrexate did not affect collagen formation in the first and second phases, but caused the abnormal proliferation and aggregation of bone cells in the 3rd phase of healing