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case_images: (A) Intraoral findings showing exposed bone (arrowheads) and the interfacing mucosa. Area of the resected oral mucosa (arrows). (B) Preoperative orthopanoramic radiograph. (C) Intraoral findings 1 year postsurgery. (D) Orthopanoramic radiograph 1 year postsurgery.
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case_images: Intraorally, necrotic bone exposure was observed, extending from the left lower canine to the second molar region (Figure 1A). In the right mandible, the osteolytic lesion was confined to the alveolar region of the molars (Figure 1B). The affected oral mucosa adjacent to the exposed bone on the left side was resected because it interfered with postsurgical wound healing (Figure 1A). The postoperative course was uneventful, and no BRONJ recurrence was observed during the 1-year follow-up (Figure 1C, D).
case_images: (A) Photomicrograph of the bone specimen showing osteomyelitis, empty osteocyte lacunae, and bacterial colonies (arrows) (hematoxylin and eosin staining, 100x, Bar: 100 microm). (B) Photomicrographs of the soft tissue specimens showing pseudoepitheliomatous hyperplasia in the epithelium and inflammatory cell infiltration in the subepithelial connective tissue (hematoxylin and eosin staining, 40x, Bar: 500 microm).
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case_images: The bone specimens presented typical histological findings, including osteomyelitis, sequestrum with empty osteocyte lacunae, and colonies of Actinomyces-like bacteria (Figure 2A). Pseudoepitheliomatous hyperplasia of the mucosal epithelium and elongation of the epithelial apices that deeply descended into the lamina propria were frequently observed in inflamed areas (Figure 2B).
case_images: (A-C and D-E) Representative photomicrographs showing micro bone fragments buried within the connective tissue, located away from the epithelium. (A, D) Hematoxylin-eosin and (B, E) Von Kossa staining of the serial sections of (A) and (D) (40x, Bar: 500 microm). (A, B) Single bone fragment is seen (arrowheads). (D, E) Various sizes of bone fragments are seen (arrowheads). Hard tissues are partly detached due to non-decalcification (*). (C, F) High-magnification view of the bone fragments in A and D. Empty osteocyte lacunae are seen within the fragments (arrows) (100x, Bar: 100 microm).
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case_images: Those fragments were considered to be necrotic bone because they were positive for Von Kossa staining and contained empty osteocyte lacunae (Figure 3).
case_images: (A-C and D-F) Photomicrographs showing PEH contacting MBFs. (A, D) Forefront of the PEH contacting MBFs of various sizes (arrowheads) (hematoxylin and eosin staining, 40x, Bar: 500 microm). (B, E) Von Kossa staining of the serial sections of (A) and (B) (40x). (C, F) High-magnification images of A and D (100x, Bar: 100 microm). MBFs contacted (arrowheads) or encompassed (arrow) by PEH.. Abbreviations: PEH, pseudoepitheliomatous hyperplasia; MBF, micro bone fragment.
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case_images: Interestingly, the forefront of the PEH occasionally contacted MBFs in submucosal connective tissues (Figure 4). Contact between the PEH and MBFs was observed in 3 of the 30 histological sections examined; in addition, complete encompassment of MBFs by the PEH was observed (Figure 4).
case_images: (A, B) Hematoxylin and eosin staining showing MBFs in contact with the PEH (40x, Bar: 500 microm). (C, D) High-magnification view of the square area in (A) and (B) (200x, Bar: 50 microm). (E, F and G, H) Immunostaining of the serial sections of (C) and (D) demonstrating epithelial cells extending downward along the MBF (arrowheads in E, G) or encompassing the MBF (arrowheads in F, H) (200x). (E, F) p63 and (G, H) CK5/6.. Abbreviations: PEH, pseudoepitheliomatous hyperplasia; MBF, micro bone fragment.
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case_images: Immunohistochemical staining of epithelial markers (p63, CK5/6) not only clearly indicated that the PEH was in contact with MBFs but also that the epithelial cells in the apices of the PEH extended downward along MBFs, seemingly beginning to encompass them (Figure 5).