Succesful dental implantation requires high osseointegration of the implant with the bone tissue that should continue for many years after implantation. Many studies on bone formation around implant have used histological evaluation, which is limited because it is qualitative. Even the information obtained using of back-scattered electron microscopic imaging are not sufficiently detailed. The purpose of this study is to determine if parametric X-ray radiation (PXR) could be used to obtain more quantitative information on newly formed bone around implants. Ti alloy implants grit-blasted with apatitic abrasive inserted in surgically created defects in rabbit tibia were retrieved after 2 weeks. Implant and tibia bone were imbedded in osteoresin, polished and sectioned (50μm) and examined using PXR.
Results showed that resolution of bone transmission images from PXR depended on the wavelength: wavelength set at 0.954A (13 KeV) did not show the newly formed bone around implants, but at wavelength set at 1.771A (7KeV) showed high resolution and clearly differentiated cortical bone from newly formed bone around implants.
This study demonstrated that hard tissue structure X-ray image observation with a high resolution was possible using PXR apparatuses, one of which was installed in the Laboratory for Electron Beam Research and Application (LEBRA) Institute of Quantum Science, Nihon University (LEBRA-PXR).

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Magnesium (Mg), strontium (Sr) or fluoride (F) ions have been shown to affect in vitro activities of bone cells and in vivo mineralization. The purpose of this study was to investigate the effect of Mg, Sr and F ions on the activities of odontoblast-like cells (MDPC-23) using an in vitro cell culture model. Mg, Sr or F ions were added to the medium in the following concentrations: Mg-1, 5, 10 mM; Sr-0.05, 0.1, 0.3, 1 mM; F-0.005, 0.01, 0.05, 0.1 mM. Results were observed after 1, 7 and 14 days using Von Kossa staining, scanning and transmission electron microscopy. Preliminary results showed the following: Mg ions demonstrated a positive effect at low concentrations and a negative effect at high concentrations; Sr ions demonstrated a positive dose dependent effect up to a concentration of 0.1 mM and a negative effect at higher concentrations; and F ions demonstrated a positive dose-dependent effect up to a concentration of 0.005 mM and inhibitory effects at higher concentrations. This preliminary study showed that the positive or negative effects of Mg, Sr or F ions on odontoblastic activities (proliferation and mineralization) depend on their concentration levels in the environment.

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Histomorphometric analyses of the mandible and femur were performed in senescence-accelerated mice (SAM) using SAMP6 as a senile osteoporosis (OP) model, SAMP8 as a temporomandibular joint osteoarthritis (TMJOA) model, and SAMR1 as control. Thirty-six male mice at 2 or 4 months of age (6 for each strain and age) were used. The cortical thickness index (CTI), bone area (B.Ar/T.Ar), trabecular width (Tb.Wi), trabecular number (Tb.N), trabecular separation (Tb.Sp), osteoblast perimeter (N.Ob/B.Pm), and osteoclast perimeter (N.Oc/B.Pm) were assessed in the distal femoral metaphysis and in the mandibular ramus including the alveolar bone. Compared with SAMR1, SAMP6 showed lower B.Ar/T.Ar and Tb.Wi in the femur and mandible at 2 and 4 months of age. This strain showed lower CTI in both bones and higher Tb.N and Tb.Sp in the femur at 4 months of age. SAMP8 showed higher CTI in both bones at 2 months of age and maintained a high index in the mandible but not in the femur at 4 months of age; however trabecular bone mass was not reduced. SAMP6 exhibited lower N.Ob/B.Pm in the femur but not in the mandible at 4 months of age, while SAMP8 showed lower N.Oc/B.Pm in the mandible but not in the femur at 2 and 4 months of age. The differential histomorphometric features of the mandible in different SAM strains may imply a difference in mandibular bone property between SAM mice with senile OP and TMJOA genetic background.

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Successful dental implant requires optimal tissue repair after implant insertion, which involves formation of new bone directly bonded to the device. The objective of this study was to use real-time PCR to investigate the temporal mRNA expression patterns of matrix metalloproteinases (MMP-2, -3, -9, -13, and -14) and tissue inhibitors of metalloproteinases (TIMP-1, -2, and -3) that contribute to tissue repair, during mineralization of MC3T3-E1 cells cultured on titanium (Ti). Lysates of the cells cultured on Ti and plastic wells (Pl) for 10 to 50 days were used for calcium and mRNA quantification. Although the onset of calcium accumulation in the cultures on Ti (30-40 days) was slower than cultures on Pl (20-30 days), the gene expression patterns during mineralization were similar in both cultures. The mRNA expression patterns of MMP-3 and -13 were distinctly different during the period from just before mineralization onset to mineralization development. The level of MMP-13 was substantial until just before the onset of mineralization but declined as mineralization developed, while MMP-3 level increased once mineralization proceeded. MMP-2, -9, and -14 and TIMP-1, -2, and -3 showed constant levels throughout. This report presents the gene expression of MMP-2, -3, -9, -13, and -14 and TIMP-1, -2, and -3 during mineralization by MC3T3-E1 cells cultured on titanium implant material, and suggest temporally distinct roles of MMP-3 and -13 in new bone formation around the implant.

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We examined the expression of HSP70 in acute lung injury induced by lipopolysaccharide (LPS), in order to explore the mechanism of HSP70 in acute lung injury. Using an acute lung injury model in Wistar rats, we observed the in vivo HSP70 expression by immunohistochemistry and Western blot. After exposure to LPS, the level of HSP70 increased above the control level at 1 hour, reached the maximum level at 2 hours, and returned to the control level by 6 hours. Our study suggested that the expression of HSP70 is involved in the protection of acute lung injury induced by LPS.

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Bone formation steadily declines with age resulting in a significant loss of bone mass, while reactive oxygen species (ROS) are thought to be major contributors to the aging process. In the present study, we attempted to identify which gene had an altered transcription level when osteoblasts were treated with ROS, H₂O₂, using a subtraction gene cloning technique. A gene clone was obtained from cDNA of cells from the osteoblastic cell line MC3T3-E1 after subtraction of the cDNA of H₂O₂-treated cells and designated as MC-ROS-7. To confirm the gene product, the DNA sequence of MC-ROS-7 was determined and homology was assessed using a nucleotide-nucleotide BLAST (BLASTN) search of the NCBI database, which revealed a 99.7% homology with fibronectin 1 (FN) gene. A significant lower level of FN mRNA was found in H₂O₂-treated cells when compared to that in non-treated cells using endpoint RT-PCR and real-time PCR assays. Our results suggest that a reduction of FN gene expression by ROS is involved in the decline of bone formation in osteoblasts during the ageing process.

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