Internal Bone Structure Research Articles

Observation of the Internal Structure of the Zygomatic Bone by Micro-Computed Tomography

The purpose of this study was to use micro-computed tomography to investigate the internal structure of the zygomatic bone, and to evaluate the effects of biting force on the zygomatic bone by comparing the internal structure of this bone between dentulous and edentulous maxillae. In this study, 20 zygomatic bones of dentulous maxillae and 28 zygomatic bones of edentulous maxillae were used (mean age: dentulous maxillae, 72.6 years; edentulous maxillae, 79.6 years). Specimens were obtained from the skulls of cadavers, from the sutura frontozygomatica, posterior to the sutura temporo-zygomatica, down to the sutura zygomatico-maxillaris. From 2-dimensional slice images, we reconstructed the three-dimensional structure by volume rendering methods using micro-computed tomography. We used two anthropological reference points: jugale Ou) at the most concave point between the lateral margin of the upper zygomatic bone and the upper margin of the zygomatic arch ; and zygomaxillare (Zm) at the lowermost point of the zygomaticomaxillary suture. We examined the structure of the zygomatic bone at Ju, Zm and the mid-point between Ju and Zm. The dentulous maxillae had thicker trabeculae at these points than the edentulous maxillae. The thicker trabecular structure in the Ju area was especially pronounced in the dentulous maxillae. These findings indicate that stress from biting force influences the trabecular structure in the zygomatic bone. They also suggest that stress in the zygomatic bone is concentrated in the Ju area, because the masseter muscle and fascia temporalis adhere to the zygomatic bone.

Parietal bone as graft material for maxillary sinus floor elevation: structure and remodeling of the donor and of recipient sites

Particulate parietal bone is used for maxillary sinus floor elevation procedure prior to dental implant placement. However, data on internal structure of the parietal bone and on graft remodeling and incorporation in the host bone are limited. We determined the structure and remodeling activities of 24 parietal bone specimens sampled at time of sinus grafting (T1 samples), and the amount and turnover of bone formed at the recipient site at time of implant placement (T2 samples, obtained 10 months after T1 samples, on average). In T1 samples, the outer cortex was 1.16+/-0.45 mm thick, had a typical haversian structure, and showed a low level of remodeling. In the cancellous portion of the samples, trabecular bone volume represented 52.8+/-10.3%. Bone remodeling was more active in the cancellous portion than in the cortical portion, but few osteoblasts and osteoclasts were seen. T2 samples consisted solely of trabecular bone, which occupied 49.4+/-18.4% of total sample volume. The boundary between new bone and the recipient bed was not discernible. Remnants of the graft particles were embedded within new bone, and showed signs of intense resorption. Bone remodeling was highly active, as shown by the presence of numerous osteoclasts resorbing new bone, together with thick osteoid seams and large osteoblasts. A loose cotton-like mineralized material was frequently observed in the marrow spaces; this acellular and non-collagenous material was strongly stained by toluidine blue, suggesting a glycoprotein nature. This study offers insights into cortical and trabecular bone structure and shows the low-level remodeling activity of parietal bone. About 10 months after grafting, the grafted chips were incorporated in new bone and almost completely resorbed. This high turnover may be beneficial for implant placement.

Long-term prediction of three-dimensional bone architecture in simulations of pre-, peri- and post-menopausal microstructural bone remodeling.

The mechanical behavior of trabecular bone depends on the internal bone structure. It is generally accepted now that the trabecular bone structure is a result of a load adaptive bone remodeling. The mathematical laws that relate bone remodeling to the local state of stress and strain, however, are still under investigation. The aim of this project was to investigate if changes in the trabecular architecture as observed with age-related bone loss and osteoporosis can be predicted from a computer model that simulates bone resorption after hormone depletion based on realistic models of trabecular microstructure using micro-computed tomography (muCT). A compact desktop muCT providing a nominal isotropic resolution of 14 mum was used to measure two groups of seven trabecular bone specimens from pre-menopausal and post-menopausal women respectively. A novel algorithm was developed to simulate age-related bone loss for the specimens in the first group. The algorithm, also referred to as simulated bone atrophy (SIBA), describes a truly three-dimensional approach and is based directly on cellular bone remodeling with an underlying realistic time frame. Bone resorption is controlled by osteoclastic penetration depth and bone formation is governed by the efficiency level of the osteoblasts. The simulation itself describes an iterative process with a cellular remodeling cycle of 197 days. Activation frequency is controllable and can be adjusted for the different phases of pre-, peri- and post-menopause. For our simulations, osteoblastic and osteoclastic activities were in balance until the onset of menopause, set to be at the age of 50 years. In that period, the structure remained almost constant. After the onset of menopause an imbalance in the cell activities was modeled resulting in a net bone loss. The doubling of the activation frequency in the peri-menopausal phase caused a pronounced loss. Using advanced animation tools and quantitative bone morphometry, the changes in bone architecture associated with the bone loss were monitored over an average observation time of 43 years until the age of 80 years. In that time, bone volume density decreased monotonously with the progression of the simulation for all specimens. Right after the onset of menopause, bone was lost fast, where with the progression of age losses slowed down. The structures at the end-point of the simulations were then compared qualitatively and quantitatively to the structures of the post-menopausal group with all morphometric indices being within a narrow margin of error. These results suggest the feasibility of transforming "normal" to "osteopenic" bone on a microstructural level yielding in realistic bone models similar in appearance as well as in structural behavior if compared to a post-menopausal group of women.

A New Computational Efficient Approach for Trabecular Bone Analysis using Beam Models Generated with Skeletonized Graph Technique

Micro-finite element (FE) analysis is a well established technique for the evaluation of the elastic properties of trabecular bone, but is limited in its application due to the large number of elements that it requires to represent the complex internal structure of the bone. In this paper, we present an alternative FE approach that makes use of a recently developed 3D-Line Skeleton Graph Analysis (LSGA) technique to represent the complex internal structure of trabecular bone as a network of simple straight beam elements in which the beams are assigned geometrical properties of the trabeculae that they represent. Since an enormous reduction of cputime can be obtained with this beam modeling approach, ranging from approximately 1,200 to 3,600 for the problems investigated here, we think that the FE modeling technique that we introduced could potentially constitute an interesting alternative for the evaluation of the elastic mechanical properties of trabecular bone.

830 ボイド粒子を分散した骨の衰退/成長モデルと過程

Growth or degeneration model of bone tissue of its internal structure is addressed. In modeling, the formation of voids in the bone's internal structure is focused and regards a volume rate and shape of void as a variable. The shape of the void is assmed in the form of a sphere or an ellipsoid. Global material characteristics of the bone is described by utilizing SCC model, a particle dispersed constitutive model based on the Self-consistent equivalent inclusion method. During the calculation, the shape and the orientation of the void are determined in the optimization adhared to the natural groth process so that the structure fits to the bone dynamics environment.

218 マイクロ X 線 CT による骨の内部構造解析

218 マイクロ X 線 CT による骨の内部構造解析

Inelastic strain accumulation in cortical bone during rapid transient tensile loading.

An experimental study examined the tensile stress-strain behavior of cortical bone during rapid load cycles to high strain amplitudes. Machined bovine and human cortical bone samples were subjected to loading cycles at a nominal load/unload rate of +/- 420 MPa/s. Loads were reversed at pre selected strain levels such that load cycles were typically completed in 0.5-0.7 seconds. Axial strain behavior demonstrated considerable nonlinearity in the first load cycle, while transverse strain behavior was essentially linear. For the human bone 29.1 percent (S.D. = 4.7 percent), and for the bovine bone 35.1 percent (S.D. = 10.8 percent) of the maximum nonlinear strain accumulated after load reversal, where nonlinear strain was defined as the difference between total strain and strain corresponding to linear elastic behavior. Average residual axial strain on unloading was 35.4 percent (S.D. = 1.2 percent) for human bone and 35.1 percent (S.D. = 2.9 percent) of maximum nonlinear strain. Corresponding significant volumetric strains and residual volumetric strains were found. The results support the conclusions that the nonlinear stress-strain behavior observed during creep loading also occurs during transient loading at physiological rates. The volume increases suggest that damage accumulation, i.e., new internal surfaces and voids, plays a major role in this behavior. The residual volume increases and associated disruptions in the internal structure of bone provide a potential stimulus for a biological repair response.

壮年期ラットの虚弱脛骨骨幹皮質骨における食餌療法に関する実験的研究 : 骨基質形成

It is of value to investigate the internal structure of bone in adulthood which is viewed as the most steady years for skeletal status. We used 17 week old rats corresponding to adulthood in human beings to induce bone loss with low calcium feeding of 3 weeks, which was followed by calcium balanced dietary therapy for another 3 weeks. The internal structure of tibial diaphyseal cortex was investigated and the results were as follows. 1. Body weight No significant differences were detected between the control and low calcium group. 2. Radiographic and densitometric findings The appearance of medial and interosseous cortices was comparable to that seen in control group, and densitometric measurement revealed no differences significantly. 3. X-ray microanalysis Calcium showed higher concentration than phosphorus in both control and low calcium group. 4. Histopathological findings Haversian systems were not present in outer and inner circumferential lamillae in low calcium group. The number of osteocytic lacunae increased around the superficial tibia and their arrangement appeared regular. In bundle bone, the number of Haversian system increased and remodelling layers were seen. The formation of bone matrix was recovered comparably with control group. 5. Hematological findings No significant differences were detected between the groups in electrocytic assessment of Ca, P, Ca/P, Na, K, Cl, biochemical evaluation such as GOP, GPT, LDH, CPK, ALP, and endocrinal examination of C-PTH, N-PTH, CT, 1, 25(OH)_2D_3. From the aforementioned results, it was concluded that formation of bone matrix recovered comparably with control group with continuing calcium balanced dietary therapy in bone loss resulting from low calcium intake in adult years.

A new method of bone tissue measurement based upon light scattering.

In recent years, time-resolved spectroscopy systems using near infrared pulsed laser have been applied to develop optical computed tomography. We applied this technique to measure the optical properties of osseous tissues. First, we gradually demineralized 10 mm blocks of bovine trabecular bone with EDTA, maintaining the absorption characteristics and structure but varying the hydroxyapatite content, thus creating specimens differing only in light scattering properties. We used computer densitograms to assess light penetration, and analyzed the correlation with bone mineral density (BMD) as with dual-energy X-ray absorptiometry scans. The light penetration increased with decreasing BMD. Second, using the above-mentioned pulsed laser time-resolved spectroscopy system, we investigated the correlation between the BMD and the time response waveforms of 10-mm blocks of bovine cortical bone, trabecular bone, and surrounding tissue as well as human trabecular bone. The human lumbar vertebral bone also displayed an inverse correlation between BMD and maximum light penetration and a positive correlation between BMD and peak time delay. This is the first demonstration of a correlation between BMD and light scattering properties showing that BMD can indeed be measured with light. Our results show the possibility of obtaining information on internal bone structure and composition in vivo through assessment of the waveforms obtained by a time-resolution system in the near infrared region.

The loss of stiffness as osteoporosis progresses

The routine diagnosis of osteoporosis is based on radiological measurements of bone mineral content. An osteoporotic failure is influenced both by a loss of mineralized bone and internal bone structure. The structure cannot be estimated by bone reconstruction based on standard radiological equipment. To investigate the influence of structure on cancellous bone stiffness, a new finite element model of cancellous bone is developed. The model describes a cancellous bone unit as an open-celled structure. Trabecular length, trabecular thickness, diameter of trabecular connections, relative lattice disorder and relative bone loss determine the real architecture. Using this model, the loss of stiffness as a result of trabecular thinning and loss of trabecular connections is estimated. The volume fraction as a scalar value for a volume can not be a marker for orthotropic stiffness changes. A formula in the form Y = e(a ∗1 n(X) + b) can describe the correlation between cancellous bone stiffness and volume fraction. these formulas are appropriate for those cases, when the loss of bone mineral (decrease in trabecular thickness) is closely connected to a loss of structure (increasingly perforated trabecular network).

Comparison of radiologic and gross examination for detection of cancer in defleshed skeletons

The reliability of visual examination of defleshed bones was assessed for detection of postcranial metastatic disease in individuals known to have had cancer. This was compared with standard clinical radiologic techniques. The skeletons of 128 diagnosed cancer patients from an early 20th century autopsied skeletal collection (Hamann-Todd Collection) were examined. Radiologic examination detected evidence of metastatic disease in 33 individuals, compared to 11 by visual examination of the postcranial skeletons. Four of these cases were detected by both techniques. Blastic lesions were most commonly overlooked on visual examination, because they were localized to trabecular (internal bone) structures. The ilium was the most commonly affected bone, with lytic or blastic lesions detected in 30 of 33 individuals. While the proximal femur was affected in only nine individuals, x-ray of the proximal femur and ilium detected all individuals with postcranial evidence of metastatic disease. Skeletal distribution of metastases provides no clue to the location of origin or histologic subtype of the cancer. Survey of archeological human remains for metastatic cancer requires radiologic examination. Such skeletal surveys should x-ray at least the ilia and femora.

成長発育期ラットの運動負荷による顎骨への影響

The mechanism of action of physical exercise and calcium intake on the jaw bones at the growth and development stage has not yet been clarified. Four-week-old male rats of Wistar strain, therefore, were used, and running exercise and food of different calcium contents were given at the same time. Their effects on the jaw bones were then investigated. The results were as follows : I. Body weight In the normal diet group, no significant differences were found from the first week through the fourth week, the calcium deficient diet group with physical exercise showed lower values (p<0.01) than the calcium deficient diet group with no physical exercise. II. Bone density findings Bone density was measured to determine degrees of bone calcifiction. No significant differences were found in the normal diet group and in the calcium deficient diet groups. Significant differences were found between the normal diet group and calcium deficient diet groups and the normal diet group showed higher values (p<0.01). III. Histopathological findings In the normal diet group, no particular changes were found in the internal structure of jaw bones from the lingual alveolar bone, central alveolar bone, buccal alveolar bone, to the labial alveolar bone. In the calcium deficient diet groups, the lingual alveolar bone, central alveolar bone, buccal alveolar bone, and labial alveolar bone showed about the same findings. In the comparison between the normal diet group and calcium deficient groups, the whole lower jaw showed extensive decrease in bone quantity for the calcium deficient groups. IV. Scanning electron microscope findings In the normal diet group and calcium deficient diet groups, no morphological changes were found in the jaw bones from the lingual alveolar bone, central aleolar bone, buccal alveolar bone, to labial alveolar bone. V. Findings in physical strength of the lower jaw bone by compression In the normal diet group and the calcium deficient diet groups, significant differences were found and the normal diet group showed higher values (p<0.01). On the basis of the foregoing findings, it was found clearly that physical exercise given to rats at the growth and development stage did not affect the jaw bones. The nutrient have an effect on the jaw bones of the rats at the growth and development stage.

Visible Light and X-Ray Ray Tracing of Generalized Cylinders

A new algorithm for ray tracing generalized cylinders whose axis is an arbitrary three-dimensional space curve and whose cross-sectional contour can be varied according to a general sweeping rule is presented. The main restriction placed on the class of generalized cylinders that can be ray-traced is that the sweeping rule of the generalized cylinder must be invertible. This algorithm handles a broader class of generalized cylinders than any other reported ray tracer. It has been integrated into a general geometric modeling system that can render objects utilizing visible light as well as simulated X rays. Generalized cylinders are often used in modeling systems because they compactly represent objects. Many commonly occurring objects including snakes, horses, airplanes, flower vases, and organs of the human abdomen such as the stomach and liver can be described naturally and conveniently in terms of one or more generalized cylinder primitives. By extending the class of generalized cylinders that can be conveniently modeled, the presented algorithm enhances the utility of modeling systems based on generalized cylinders. X-ray images of the internal bone structure of a knee joint and a visible light image of a fan blade assembly are presented.

Visible Light and X-Ray Ray Tracing of Generalized Cylinders

A new algorithm for ray tracing generalized cylinders whose axis is an arbitrary three-dimensional space curve and whose cross-sectional contour can be varied according to a general sweeping rule is presented. The main restriction placed on the class of generalized cylinders that can be ray-traced is that the sweeping rule of the generalized cylinder must be invertible. This algorithm handles a broader class of generalized cylinders than any other reported ray tracer. It has been integrated into a general geometric modeling system that can render objects utilizing visible light as well as simulated X rays. Generalized cylinders are often used in modeling systems because they compactly represent objects. Many commonly occurring objects including snakes, horses, airplanes, flower vases, and organs of the human abdomen such as the stomach and liver can be described naturally and conveniently in terms of one or more generalized cylinder primitives. By extending the class of generalized cylinders that can be conveniently modeled, the presented algorithm enhances the utility of modeling systems based on generalized cylinders. X-ray images of the internal bone structure of a knee joint and a visible light image of a fan blade assembly are presented.

Structure and Mineral Content in Weight-Bearing Bones Following Hindlimb Suspension in Young Rats.

Responses of structure and mineral content in weight-bearing bones to 1-week hindlimb suspension were studied in growing rats. The weight, volume, and length of femur, tibia, and fibula were less in suspended rats than cage controls, although there was no significant difference in the weight/volume ratio. The diameter of mid-shaft, the thickness of cortical bone, and the ratio of cortical bone thickness to femur diameter were significantly less in the suspended rats. The width of marrow space showed no differences, suggesting that the cortical bone was mainly affected. The sum of mineral content and the mineral content per diameter in the cross section of femurs were decreased following suspension, suggesting a change in the internal structure of cortical bone. Data also indicated that the reduction of femur diameter was caused by decreased thickness which is accompanied by the decreased mineral content of the cortical bone. It was suggested that there is a close relationship between the responses of bones and muscles to hindlimb suspension of young rats, although the degree of weight loss was greater in muscles than in bones.

Skeletal biology and individual life history of Gombe chimpanzees

Skeletons of Gombe chimpanzees representing both sexes and ages from infancy to old age are examined in detail by a variety of techniques. The combination of biological and lifetime behavioural data presents an integrated view of individuals which make up a local population. These skeletons reflect species‐patterned growth, development and ageing. Furthermore, individual variation is related to lifetime experiences: for example, the impact of nutrition, injury and disease on survival and reproduction in the physical and psychosocial environments. Size, shape and internal structure of bones and teeth record life‐history features associated with both primary and secondary life‐history characters. These case studies emphasize the role of the individual in the evolutionary process.

Visualization of the Human Periodontium Using Serial Thin Section Contact Radiography

A method is described to produce radiographs of thin sections of human teeth and periodontal structures. These high resolution contact x-rays allow for visualization of the microscopic details of the mineralized components of these tissues in a dimension heretofore not examined. Twenty-five blocks of human jaws containing teeth affected by periodontal disease were obtained from cadavers. Sagittal, transverse and cross-sectional serial slices were cut using a rotary instrument (1500 rpm) with a water-cooled 3-inch jewelers slot saw. Five hundred-micron sections were made of jaw specimens containing 2 or 3 teeth. The radiographs were taken with a Faxitron low voltage x-ray machine on Kodak-Ortho, Type 3 film. Films were exposed at a distance of 12 inches from the x-ray source at 35 kVp and 1.0 mA for 3 minutes with the specimen in direct contact with the film. Spatial representation of the internal structure of the alveolar bone was obtained using this technique and the detailed anatomy of the vascular channels within the cancellous and cortical compartments of the jaws was studied. Mineralization patterns of plaque and calculus, calcifications in the periodontal ligament, pulp calcifications, accessory root canals, caries and detailed structural changes in the enamel and cementum were also viewed on these films with the aid of microscopy. Magnifications of up to 30 times were used without excessive image distortion resulting from film grain.

The relationship of trabecular architecture to inferred loading patterns in the third metacarpals of the extinct equids Merychippus and Mesohippus

The internal structures of the third metacarpals of Merychippus and Mesohippus are assessed from thin sections and from radiographs, and systems of trabeculae differing in orientation and density are described. The principal forces transmitted to the articular surfaces of these bones are reconstructed and are used to estimate the pressure of contact on each surface. The major correlations made between the structure and the function of the third metacarpal of Equus (Thomason, 1985a) are also observed in this bone in Merychippus and Mesohippus. More important, the differences in trabecular structure among the recent and fossil bones may be interpreted in terms of the differences in inferred function. Thus the functional interpretation of the internal structure of fossil bones may reasonably be attempted.

Osteoporosis. An update on management.

Osteoporosis is the reduction of expected bone mass. This results in structural failure with an increased risk of fracture and it is the most common bone disorder encountered. Bone mass declines with age, and in some people will fall below the threshold for easy fracture. This loss is accelerated in the postmenopausal period. Trauma and the internal trabecular structure of bone are additional determinants of risk of fracture. Effective management of osteoporosis depends on identifying and treating those at risk before reaching the critical bone mass and presenting with skeletal failure. There are limitations to methods available for assessing bone loss, and the final arbiter of any treatment is prevention of fracture. Primary prevention involves maximising peak adult bone mass and reducing the rate of bone loss. This may be attained by exercise, adequate dietary calcium, and the identification and treatment of risk factors such as postmenopausal hormone replacement. Once skeletal failure has occurred, long term treatment is required to have a clinically significant effect. Increasing bone mass cannot be assumed to reduce the risk of fracture, and such a reduction has not been directly demonstrated for several agents. Calcium supplements, hormone replacement therapy and fluoride are probably effective in reducing fracture rate, particularly when used in combination, whereas the efficacy of anabolic steroids, calcitonin and diphosphonates is yet to be established. Vitamin D is only of use in coexistent osteomalacia. The limitation of significantly strengthening the skeleton during the life expectancy of the elderly must be realised.

Developments in the identification of human skeletal material (1968–1978)

A review of publications over the last ten years of methods in the field of physical anthropology for determining age, sex, race and stature of human skeletal material is presented. Comparisons are made with the types of papers published in the previous ten years (1958-1968) in six categories: (1) Visual examination of bones (2) Anthropometric measurements of bones (3) Anthropometric measurements with subsequent use of statistics in the form of discriminate function analyses (4) Time and sequence of eruption of the teeth (5) X-ray examination of the internal structure of bone sections (6) Microscopic examination of the internal structure of bone.