Experimental investigation of xenograft mixed with doxycycline, rifamycin, metronidazole and clindamycin in critical sized bone defects after radiotherapy

Patients undergoing cancer treatment and radiotherapy in the head- neck region are at risk for the development of osteoradionecrosis of the jaws. In the ischemic regions, bone healing can be delayed. Infection exacerbates clinical manifestations. Antibiotics are clinically effective on the prevention or treatment of infections and have to be used for long- term. Recently, antibiotics have been thought to have antiinflammatory effects independent of their antibacterial activities and thus contribute to bone healing. We examined the effects of clindamycin, metronidazole, rifamycin and doxycycline mixed with xenograft on bone healing in critical-sized surgical defects in mandible which had been previously exposed to radiation. 50 Wistar albino rats were used. After radiotherapy to every, bicortical bony defects in 5 mm diameter was created in the right mandible of rats, filled with antibiotics and xenograft in the experimental groups, and with only xenograft particles in the control groups. After surgery, sacrifications were performed at fourth week and all specimens were evaluated histologically and histomorphometrically in terms of inflammation, necrosis, fibrosis, new bone formation areas, calcified trabecular bone areas and capillary count. None of the specimens showed symptoms of necrosis, infection or fibrosis. The new bone formation areas were significantly higher in Metronidazole and Clindamycin groups when compared with control group (p <0.01, p <0.01). When the calcified bone trabecular areas were examined, there was a statistically significant difference between the control and Clindamycin group (p <0.01). When Clindamycin was compared with other groups, the difference was also significant (p <0.05). The capillary count was significantly different in the Metronidazole (p <0.05) and Clindamycin groups when compared with the control group (p <0.01). Inflammatory reactions decreased in the groups treated with antibiotics, new bone formation areas and vascularity were increased. Antibiotics might have anti- inflammatory activities independent of their antibacterial properties.