Microstructural Observation with MicroCT and Histological Analysis of Human Alveolar Bone Biopsy from a Planned Implant Site: A Case Report
The patient was a 53-year-old male. About 30 years previously, his lower left first molar had been extracted at a private dental clinic following severe dental caries, with a fixed dental bridge having been constructed in the region of the missing tooth. Approximately fourteen years later in 1991, a new fixed bridge was constructed at the same site, at our hospital’s dental clinic. In 2005, the patient returned, and requested implant treatment to replace the bridge (Fig. ).\nBefore surgery, periapical radiographs, panoramic radiograph, and CT images of the mandible were taken. The CT scanning was performed at the following settings: slice thickness 1.0 mm; 120 kV and 100 mA (Xvigor Real; Toshiba Medical Systems Co., Ltd., Tochigi, Japan). Bone turnover markers, including serum bone-specific alkaline phosphatase (BAP), serum osteocalcin (OC), serum type I collagen cross-linked N-telopeptide (NTX) and urinary deoxypyridinoline (DPD) were examined as part of the biochemical testing of the patient’s systemic bone metabolism. A calcaneal quantitative ultrasound measurement was performed using Speed of Sound (SOS) with an ultrasound device (CM-200; Furuno Electric Co., Ltd., Hyogo, Japan).\nUsing a trephine bur, an alveolar bone sample (column-shaped; 2 mm in diameter, 7 mm in height) was obtained from the implant site (Fig. ), before the the implant was placed (5 mm in diameter, 13 mm in height, Brånemark system®, Nobel Biocare, Gothenburg, Sweden). The sample was fixed in 4% formaldehyde solution for 24 hours.\nAfter fixation, the fine trabecular structures of the sample were observed with microCT (Fig. ), at the following settings: slice thickness 20 µm; magnification 4.58X; 80.0 kV and 76 µA (ELE SCAN; Nittetsu. Elex Co., Ltd., Tokyo, Japan). The sample was then decalcified, embedded in paraffin and sliced into thin sections for hematoxylin-eosin staining (Fig. ) and tartrate-resistant acid phosphatase (TRAP) staining. Bone histomorphometry was performed on three selected longitudinal sections, one through the center of the sample and the other two 0.5 mm from the central one, using bone histomorphometry system software (System Supply Co. Ltd, Nagano, Japan), and measurements were made of the following parameters: bone volume (%), trabecular thickness (µm), osteoblast surface (%), eroded surface (%), quiescent surface (%), trabecular number (N), trabecular separation (µm), erosion depth (µm) []. All data for the three sections was expressed as means and standard deviations.\nThe patient enrolled in the study received a verbal and written explanation of its goals and procedures, and subsequently signed an informed consent form, prior to participating in the study. All the procedures involved had already been approved by the Niigata University Ethics Committee (20-R13-08-06).\nThe panoramic and periapical radiographs revealed an irregularly-shaped radiolucency under the alveolar crest at the planned implant site (Fig. ), and the trabeculae were not clearly visible with ordinary CT (Fig. ). Blood and urine analyses indicated that the patient’s bone metabolism was within the normal range (Table ). The calcaneal bone density was slightly lower than the average for the same age group, but still within the standard deviation (SD) range (Table ). MicroCT three-dimensional (3D) images of the bone sample clearly showed several plate-like trabeculae extending outward from the lingual cortical bone (Fig. ). These trabeculae were poorly connected and widely separated.\nHistological observations revealed that the marrow space was filled with adipose tissue (Fig. ), and that most of the bone surface was covered with flattened osteoblasts (Figs. , ). However, some hematopoietic cells were observed in the bone marrow (Fig. ), and cuboidal osteoblasts were also seen on the bone surface in a few regions (Fig. ). A small number of TRAP-positive osteoclasts and cement lines were also observed (Figs. , ). The histomophometricdata are shown in Table .\nThe dental implant is still functioning well, with no bone loss detectable on X-rays (Fig. ) and no clinical problems two years post-operatively (Fig. ).