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)

Mucoperiosteal flaps are used to access the bone and root surface in a wide range of periodontal procedures and in implant surgery. We have demonstrated that the mucoperiosteal surgical flap of the rat mandible produces a transient burst of alveolar bone resorption similar to the clinical observations in humans. This resorptive activity, when coupled with local irritation factors, may cause confined alveolar bone loss. Recently, we have demonstrated that an amino bisphosphonate, which is used in preventing systemic bone resorption in osteoporosis and other bone diseases, reduces alveolar bone resorption in the rat model when administered systemically. In this study we evaluated the effect of local delivery of the amino bisphosphonate on bone resorption associated with mucoperiosteal flaps. Following mucoperiosteal flap elevation in the premolar and molar region of the rat mandible, a surgical pellet soaked with amino bisphosphonate was locally applied on the exposed bone surface and covered by flap. The results show that local delivery of amino bisphosphonate reduces significantly alveolar bone resorption activated by mucoperiosteal flap surgery. This study suggests that local application of amino bisphosphonate can be used as an adjunct in therapy for reducing bone resorption following surgery. J Periodontol 1997;68:884–889.

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Following elevation of a full thickness flap a transient burst of regional remodeling occurs. This phenomenon is termed in orthopedic surgery as regional accelerated phenomenon (RAP), beginning with accelerated resorption activity followed by a slow process of bone regeneration. Recently we have demonstrated that a mucoperiosteal surgical flap of rat mandible is producing a typical RAP process. Bisphosphonates are synthetic compounds that are taken up preferentially by the skeleton and suppress osteoclast‐mediated bone resorption by a mechanism that is not yet fully understood. Amino bisphosphonate has been shown to inhibit active bone resorption without interfering with bone formation. In this study we evaluated the effect of amino bisphosphonate on bone resorption associated with a mucoperiosteal flap used as a resorptive model. We compared the effect of amino bisphosphonate in rats using IV administration with topical application at 3 dose levels. The results show that topical application of all 3 doses (0.15, 0.75, and 1.5 mg/ml) had no inhibiting effect on bone resorption after surgery, while IV administration at 0.5 mg/kg body weight significantly reduced the bone resorption. Interestingly, in the non‐operated side, amino bisphosphonate increased mineral density. J Periodontol 1995;66:999–1003.

This study implies that topical delivery of alendronate at the time of surgery reduces bone loss in periodontal procedures involving mucoperiosteal flap surgery. The most effective dose is 200 microg for topical delivery at the surgical site and 400 microg for distant sites.