Figure 2. Representative microscopic images from immunofluorescence staining of MMP-2 (left images) and MMP-9 (right images) in dogs' apical and periapical tissues. A and B: healthy tooth showing positive and mild expression of MMP-2 in membrane and cytoplasm of fibroblasts at the periodontal ligament space, cementoblasts, and osteoblasts, and MMP-9 in osteoblasts present in mature bone. C and D: tooth with untreated periapical lesions presenting positive and severe immunostaining of MMP-2 and MMP-9 in cementocyte lacunae, inflammatory infiltrate cells, and cementoblasts. E and F: periapical lesions endodontically treated in a single session presented severe expression of MMP-2 and MMP-9 in persistent cells of inflammatory infiltrate and cementocyte lacunae. G and H: periapical lesions treated with EGCG-based paste presented mild expression of MMP-2 and MMP-9 located in cementocytes, cementoblasts, and osteoblasts lining repaired alveolar bone surface. I and J: periapical lesions treated with calcium hydroxide-based paste showed a positive and mild expression of MMP-2 and MMP-9 in cementoblasts and fibroblasts. Fluorescence microscopy. Magnification: A, C-F: 10X; B 20X; G-J: 40X.