Immediate versus delayed application of bone morphogenetic protein-2 solution in damaged extraction sockets: a preclinical in vivo investigation

Abstract

To compare the clinical, radiographic, and histological healing patterns between the immediate and delayed applications of bone morphogenetic protein-2 (BMP-2) in damaged extraction sockets in dogs. The distal roots of the fourth premolars of the mandible were extracted bilaterally in five beagle dogs, and buccal bone defects (4mm wide and 9mm high) were surgically created. Collagenated biphasic calcium phosphate (CBCP) soaked for 10min in 100μL of BMP-2 solution was applied immediately to the defect site in the control group. In the test group, the BMP-2 solution of same dose was injected into the grafted site 2weeks after grafting with a saline-soaked CBCP. The dogs were sacrificed 2weeks later. Clinical, histological, and radiographic analyses were followed. Swelling and inflammatory reactions were predominantly observed in the control group at 2weeks. The area of new bone formation was significantly larger in the control group compared with the test group (10.8 ± 7.0 mm2 [mean ± SD] and 6.3 ± 3.1 mm2, respectively; p = 0.043). No significant difference was found in ridge width at 2mm, 4mm and 6mm below the lingual bone crest between the control (2.6 ± 1.0mm, 3.2 ± 0.9mm and 4.5 ± 0.5mm, respectively) and test group (3.3 ± 1.0mm, 3.7 ± 1.3mm and 4.2 ± 1.0mm; all p > 0.05). Delayed application of BMP-2 2weeks after surgery did not show any advantage over immediate application of BMP-2 in terms of new bone formation. This study suggests that it might be better to apply BMP-2 immediately in alveolar ridge preservation, instead of delayed application, in order to enhance new bone formation.