(A) Alveolar bone loss was determined in palatal bone samples stained with 1% methylene blue and photographed at 30× magnification using a dissecting microscope with the occlusal face of the molars perpendicular to the base. The distance between the cementoenamel junction and the alveolar crest was measured at 6 sites in APN−/−, APN−/−+PD, APN−/−+PD+APN, as well as WT and WT+PD mice (magnification, ×30). (B) TRAP staining determined the number of osteoclasts (magnification, ×200; scale bars, 500 µm). (C) H&E staining determined the number of inflammatory cells of palatal bone samples in APN−/−, APN−/−+PD, APN−/−+PD+APN, as well as WT and WT+PD mice (magnification, ×400; scale bars, 20 µm; black arrows = inflammatory cells). Data are shown as mean ± SD (n = 5). *P<0.05.