Ratoc System Engineering Co.

Tokyo, Japan

Ratoc System Engineering Co.

Tokyo, Japan
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Wada K.,Tokyo Medical and Dental University | Miyashin M.,Tokyo Medical and Dental University | Nango N.,RATOC System Engineering Co. | Takagi Y.,Tokyo Medical and Dental University
American Journal of Dentistry | Year: 2011

Purpose: To determine whether resin composites are appropriate for full crown restoration of primary molars by evaluating their wear characteristics. Specifically, the wear properties of resin composite specimens and the opposing enamel surfaces were characterized by means of impacting-sliding wear testing. Methods: Three types of light-cured resin composites (Estelite Squick, Litefill IIP, and Metafil C), one type of chemical-cured resin composite (Clearfil FII), and a hybrid composite (Estenia C&B) were tested in this study. The enamel sample was used as the control. The hemispherically prepared specimens were subjected to impacting-sliding wear testing against the flattened enamel of primary molars. The worn surfaces were examined by laser scanning microscopy and scanning electron microscopy. The volumetric loss was estimated by using micro-CT images. The areas of worn enamel surfaces were measured by 3D color laser microscopy. On most of the worn enamel surfaces, cracks appeared. Scatter plot analyses between their width and depth were carried out. Data for each specimen were statistically analyzed by multiple comparisons among the means of treatment by Bonferronis method (P< 0.01). Results: Clearfil showed significantly higher surface area wear, volumetric loss, and worn enamel surface area than did the other resin composites and the control enamel (P< 0.01). There was no significant difference among the worn surface areas of Estelite, Litefill, Metafil, and Estenia (P< 0.01). The control enamel showed significantly lower worn surface area than did the resin composites (P< 0.01). There was no significant difference in volumetric loss and worn enamel surface areas among Estelite, Litefill, Metafil, Estenia, and the control enamel (P< 0.01). Cracks larger than that on the control enamel were seen on the worn enamel surface opposing Estenia.

Kanzaki S.,Keio University | Takada Y.,Keio University | Takada Y.,Rigaku Corporation | Niida S.,National Center for Geriatrics and Gerontology | And 6 more authors.
American Journal of Pathology | Year: 2011

In the middle ear, a chain of three tiny bones (ie, malleus, incus, and stapes) vibrates to transmit sound from the tympanic membrane to the inner ear. Little is known about whether and how bone-resorbing osteoclasts play a role in the vibration of auditory ossicles. We analyzed hearing function and morphological features of auditory ossicles in osteopetrotic mice, which lack osteoclasts because of the deficiency of either cytokine RANKL or transcription factor c-Fos. The auditory brainstem response showed that mice of both genotypes experienced hearing loss, and laser Doppler vibrometry revealed that the malleus behind the tympanic membrane failed to vibrate. Histological analysis and X-ray tomographic microscopy using synchrotron radiation showed that auditory ossicles in osteopetrotic mice were thicker and more cartilaginous than those in control mice. Most interestingly, the malleal processus brevis touched the medial wall of the tympanic cavity in osteopetrotic mice, which was also the case for c-Src kinase-deficient mice (with normal numbers of nonresorbing osteoclasts). Osteopetrotic mice showed a smaller volume of the tympanic cavity but had larger auditory ossicles compared with controls. These data suggest that osteoclastic bone resorption is required for thinning of auditory ossicles and enlargement of the tympanic cavity so that auditory ossicles vibrate freely. Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Nango N.,Ratoc System Engineering Co. | Kubota S.,Ratoc System Engineering Co. | Takeuchi A.,Japan Synchrotron Radiation Research Institute | Suzuki Y.,Japan Synchrotron Radiation Research Institute | And 3 more authors.
Biomedical Optics Express | Year: 2013

The three-dimensional network of lacunae and canaliculi that regulates metabolism in bone contains osteocytes and their dendritic processes. We constructed a synchrotron radiation X-ray microscope for sequential tomography of mouse tibia first by using a Talbot interferometer to detect the degree of bone mineralization and then by using absorption contrast under a slightly defocused setting to enhance outline contrast thereby visualizing structures of the osteocyte lacuno-canalicular network. The resultant pair of tomograms was precisely aligned with each other, allowing evaluation of mineral density in the vicinity of each osteocyte lacuna and canaliculus over the entire thickness of the cortical bone. Thus, multiscan microscopic X-ray tomography is a powerful tool for analyzing bone mineralization in relation to the lacuno-canalicular network at the submicron resolution level. ©2013 Optical Society of America.

PubMed | Shiga University of Medical Science, Rigaku Corporation, National Cancer Research Center, Tohoku University and 2 more.
Type: Journal Article | Journal: Development (Cambridge, England) | Year: 2015

Endochondral ossification is a developmental process by which cartilage is replaced by bone. Terminally differentiated hypertrophic chondrocytes are calcified, vascularized, and removed by chondroclasts before bone matrix is laid down by osteoblasts. In mammals, the malleus is one of three auditory ossicles that transmit vibrations of the tympanic membrane to the inner ear. The malleus is formed from a cartilaginous precursor without growth plate involvement, but little is known about how bones of this type undergo endochondral ossification. Here, we demonstrate that in the processus brevis of the malleus, clusters of osteoblasts surrounding the capillary loop produce bone matrix, causing the volume of the capillary lumen to decrease rapidly in post-weaning mice. Synchrotron X-ray tomographic microscopy revealed a concentric, cylindrical arrangement of osteocyte lacunae along capillaries, indicative of pericapillary bone formation. Moreover, we report that overexpression of Fosl1, which encodes a component of the AP-1 transcription factor complex, in osteoblasts significantly blocked malleal capillary narrowing. These data suggest that osteoblast/endothelial cell interactions control growth plate-free endochondral ossification through osteogenic capillaries in a Fosl1-regulated manner.

PubMed | Toho University and Ratoc System Engineering Co.
Type: Journal Article | Journal: Journal of orthopaedic surgery (Hong Kong) | Year: 2016

To compare bone mineral density (BMD) in patients with or without weekly injection of teriparatide to promote bone ingrowth after cementless total knee arthroplasty (TKA).Records of 8 men and 32 women (mean age, 75.6 years) who underwent cementless TKA for medial knee osteoarthritis with (n=20) or without (n=20) once-weekly subcutaneous/hypodermic injection of teriparatide for 48 weeks were reviewed. BMD and bone volume/total volume (BV/TV) of the bone-prosthesis interface of the proximal tibia in 6 regions of interest (ROI) were assessed at 3, 6, 9, and 12 months using multi-detector computed tomography.Patients with or without weekly injection of teriparatide after cementless TKA were comparable in terms of baseline characteristics and pre- and post-operative knee range of motion and Knee Society knee and function scores. In ROI 1 (medial), ROI 3 (anteromedial), and ROI 4 (posteromedial), the BV/TV increased throughout the postoperative period in patients with weekly injection of teriparatide and declined after 6 months in patients without weekly injection of teriparatide. These 3 ROIs of the 2 groups differed significantly only in BMD at 6, 9, and 12 months. In ROI 2 (lateral), ROI 5 (anterolateral), and ROI 6 (posterolateral), both BV/TV and BMD showed a decreasing trend, and these 3 ROIs of the 2 groups did not differ significantly.Weekly injection of teriparatide after cementless TKA promoted bone ingrowth mostly in the medial aspect of the bone-prosthesis interface.

Iwamoto J.,Keiyu Orthopaedic Hospital | Seki A.,Hamri Co. | Nango N.,Ratoc System Engineering Co.
Calcified Tissue International | Year: 2016

Teriparatide (TPTD) is known to increase the cortical thickness and porosity. The purpose of the present study was to determine whether switching from TPTD to ibandronate (IBN) would be useful for improving cortical bone parameters as assessed using high-resolution quantitative computed tomography (HR-QCT) analyses in mature rabbits. Forty-two female New Zealand white rabbits (18–22 weeks old) were randomized into six groups of 7 animals each as follows: 4-week vehicle administration group, 4-week TPTD administration group (20 μg/kg, subcutaneously [s.c.], daily), 12-week vehicle administration group, 4-week TPTD administration + 8-week vehicle administration group, 4-week TPTD administration + 8-week lower-dose IBN administration group (20 μg/kg, s.c., every 4 weeks), and 4-week TPTD administration + 8-week higher-dose IBN administration group (100 μg/kg, s.c., every 4 weeks). After the 4- or 12-week experimental period, the cortical bone of the distal femoral diaphysis was processed for HR-QCT analysis. The 4-week TPTD administration increased the pore ratio, number, and density as well as the cortical area, thickness, and bone mineral content (BMC), without significant influencing the volumetric bone mineral density (BMD). The 4-week TPTD administration + 8-week vehicle administration decreased the pore ratio, number, and density as well as the cortical area and thickness, compared with the 4-week TPTD administration, but the pore ratio, cortical area, and thickness were still higher compared with the 12-week vehicle administration. The 4-week TPTD administration + 8-week higher-dose IBN administration, but not the 4-week TPTD administration + 8-week lower-dose IBN administration, increased the cortical area, thickness, BMC, and volumetric BMD and decreased the pore ratio, but not the pore number or density, compared with the 4-week TPTD administration + 8-week vehicle administration. These results suggest that higher-dose IBN after TPTD therapy has a beneficial effect on the BMC, volumetric BMD, cortical area, thickness, and porosity in mature rabbits. © 2016 Springer Science+Business Media New York

Wayama M.,University of Tokyo | Ota S.,University of Tokyo | Ota S.,Japan Science and Technology Agency | Matsuura H.,University of Tokyo | And 4 more authors.
PLoS ONE | Year: 2013

Haematococcus pluvialis is a freshwater species of green algae and is well known for its accumulation of the strong antioxidant astaxanthin, which is used in aquaculture, various pharmaceuticals, and cosmetics. High levels of astaxanthin are present in cysts, which rapidly accumulate when the environmental conditions become unfavorable for normal cell growth. It is not understood, however, how accumulation of high levels of astaxanthin, which is soluble in oil, becomes possible during encystment. Here, we performed ultrastructural 3D reconstruction based on over 350 serial sections per cell to visualize the dynamics of astaxanthin accumulation and subcellular changes during the encystment of H. pluvialis. This study showcases the marked changes in subcellular elements, such as chloroplast degeneration, in the transition from green coccoid cells to red cyst cells during encystment. In green coccoid cells, chloroplasts accounted for 41.7% of the total cell volume, whereas the relative volume of astaxanthin was very low (0.2%). In contrast, oil droplets containing astaxanthin predominated in cyst cells (52.2%), in which the total chloroplast volume was markedly decreased (9.7%). Volumetric observations also demonstrated that the relative volumes of the cell wall, starch grains, pyrenoids, mitochondria, the Golgi apparatus, and the nucleus in a cyst cell are smaller than those in green coccid cells. Our data indicated that chloroplasts are degraded, resulting in a net-like morphology, but do not completely disappear, even at the red cyst stage. © 2013 Wayama et al.

Nakata K.,Tokyo Medical and Dental University | Nikaido T.,Tokyo Medical and Dental University | Nakashima S.,Tokyo Medical and Dental University | Nango N.,Ratoc System Engineering Co. | Tagami J.,Tokyo Medical and Dental University
Dental Materials Journal | Year: 2012

To indicate the possibility of a new approach to creating mineral density profiles, and to examine longitudinal changes in 'the rate of remineralization (R A)' and 'the mineral density (D As) at 4 different depths' (surface zone: SZ, lesion body: LB, middle zone: MZ, deep zone near to sound area: DZ) in enamel subsurface lesions, eight demineralized bovine enamel-dentin blocks were remineralized for 1 to 4 week and investigated using Micro-focus X-ray CT (micro-CT). After CT scanning, mineral density profiles were created. Mineral densities at each depth after demineralization were SZ≅LBMZ>DZ. This study indicated a new approach to create a mineral density profile and suggested the greater the value of the mineral density before the remineralization, the smaller the mineral density increments.

Okazaki N.,Nagasaki University | Chiba K.,Nagasaki University | Taguchi K.,Nagasaki University | Nango N.,Ratoc System Engineering Co. | And 3 more authors.
Bone | Year: 2014

Trabecular bone microfracture pathogenesis and associated healing processes are not well understood. We analyzed the microcalluses that form subsequent to microfractures in patients with osteoporosis (OP) using synchrotron radiation micro CT (SRCT).Subchondral bone columns were extracted from the femoral heads of 11 female patients with a femoral neck fracture. SRCT scanning was performed with 5.9×5.9×5.9μm3 voxel size and the microcallus number was measured in a 5-mm cubic subchondral bone region. The trabecular bone microstructure was measured and its relationship to the microcallus number was analyzed. In addition, the degree of mineralization of the microcallus region and that of the rest of the trabecular bone were measured and compared.Microcallus formations were detected in all cases, with a mean microcallus number of 4.9 (range, 2-11). The microcallus number had a significantly negative correlation with bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and degree of mineralization, and had a positive correlation with specific bone surface (BS/BV). The degree of mineralization of the microcallus region was lower than that of the rest of the trabecular bone and had a wider range of values.Microcallus formations were frequently detected in patients with OP, and more prevalent in the bone with thinner trabeculae, suggesting microfractures might occur due to activities of daily living as the OP progresses. The degree of mineralization of microcallus might represent the process of bone healing from immature woven bone to mature trabecular bone. © 2014 Elsevier Inc.

Chiba K.,Nagasaki University | Nango N.,Ratoc System Engineering Co. | Kubota S.,Ratoc System Engineering Co. | Okazaki N.,Nagasaki University | And 3 more authors.
Journal of Bone and Mineral Research | Year: 2012

We analyzed the microstructure and degree of mineralization of the subchondral trabecular bone in hip osteoarthritis (OA) using synchrotron radiation computed tomography (SRCT) to identify the relationship between bone structure and bone turnover. Subchondral bone samples were extracted from femoral heads of 10 terminal-staged hip OA patients. The SRCT scan was performed at 30 keV energy and 5.9 μm voxel size. Trabecular bone structure, bone cyst volume, and the degree of trabecular bone mineralization were measured, and correlations between bone structure and the degree of mineralization were analyzed. In addition, the trabecular bone was divided into the area immediately surrounding the bone cyst and the remaining area, and they were compared. The average cyst volume fraction in the whole region was 31.8%, and the bone volume fraction in the bone region was 55.6%. Cyst volume was the only structural parameter that had a significant correlation with the degree of mineralization. The degree of mineralization was diminished when the bone cyst was larger (r=-0.81, p=0.004). The trabecular bone immediately surrounding the bone cyst had a lower degree of mineralization when compared with the remaining trabecular bone (p=0.008). In the bone sclerosis of OA subchondral bone, there are many large and small bone cysts, which are expected to play a significant part in the high bone turnover of OA. © 2012 American Society for Bone and Mineral Research.

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