The purpose of this study was to evaluate the effect of fibronectin application on healing of replanted teeth. Three rhesus monkeys were used. Maxillary and mandibular incisors and premolars were extracted and replanted. Teeth were extracted with forceps and placed in saline solution. After 5 minutes, each tooth was returned to its socket and immobilized by interproximal acid-etch splints, which were removed after 1 week. Of the forty-eight teeth replanted, twenty-four control teeth were replanted as described. On each of the remaining teeth, the root surface and the inner walls of the socket were bathed with 1 ml of fibronectin in saline solution (400 micrograms/ml) during the 5-minute interval between tooth extraction and its replantation. Replanted teeth and animal killings were scheduled to provide observations 1, 3, 7, 14, 28, and 45 days after replantation. Each monkey received an intravenous injection of tritiated thymidine, 1 microCi/g body weight, 1 hour before it was killed. Tissue specimens were processed for histologic and autoradiographic evaluation following standard procedures. For each of the six points of time, four pairs of contralateral teeth were available for evaluation; four teeth were treated with fibronectin and four without it. The findings of this study indicate that fibronectin use resulted in enhanced healing by early replacement of the fibrin clot, increased connective tissue cell proliferation, reduction of the inflammatory response, and inhibition of both cementum resorption and dentoalveolar ankylosis.