Striking remodeling activity occurs adjacent to the site of injury in orthopedic surgery. This reaction has been described as regional accelerated phenomenon (RAP), as it speeds up the healing stage. The phenomenon is a transient burst of localized remodeling process following surgical wounding of cortical bone. We explored whether RAP occurs following mucoperiosteal flap surgery in the jaw bone. Mucoperiosteal flaps were performed on 60 Wistar rats, either only on the buccal aspect or both on buccal and lingual aspects of the mandible. The surgical procedure lasted an average of 30 seconds and the flap was readapted without sutures. The rats were sacrificed at 3, 7, 10, 14, 21, and 120 days. High resolution x-ray microradiography of 1 to 1.5 mm thick ground sections between premolar and molar regions of the mandible were analyzed and revealed large areas of radiolucency which correlated to massive resorption of the alveolar bone, as well as areas in the bone proper. The RAP was observed as early as 10 days in the treated side group. Striking resorption of the cortical bone, both on the surface and the bone proper, occurred on the periodontal aspect of the crestal bone leading to widening of the periodontal ligament space, where a mucoperiosteal flap was performed on the buccal aspect. The resorption was more prominent when a mucoperiosteal flap was performed both on the lingual and buccal aspect. The alveolar bone recovered almost to control levels 120 days after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)