BMP-2/4 expression was increased at the protein and mRNA levels in BP-altered oral mucoperiosteum. (a) Rarely, there was pronounced BMP-2/4 staining in healthy jaw periosteum. (b) BMP-2/4-expressing osteocytes showed higher cellular density in the BONJ group. (c) The labeling index of BMP-2/4-expressing osteoblasts and osteocytes was significantly increased compared to control (Controls-ME: 22.06, IQR 25.0 vs. BONJ-ME: 53.97, IQR: 25.0; p < 0.05). (d) Relative BMP-2 gene expression at the mRNA level was elevated 8.9-fold in ONJ samples (Controls-ME: 1.14, IQR 1.07 vs. BONJ-ME: 8.9, IQR: 6.1; p < 0.02) related to healthy samples. Horizontal bars indicate median (ME), and error bars indicate interquartile range (IQR).