Articular cartilage covers the temporomandibular joint (TMJ) and provides smooth and nearly frictionless articulation while distributing mechanical loads to the subchondral bone. The thickness of the cartilage is considered to be an indicator of the stage of development, maturation, aging, loading history, and disease. The aim of our study was to develop a method for ex vivo assessment of the thickness of the cartilage that covers the TMJ and to compare that with two other existing methods. Eight porcine TMJ condyles were used to measure cartilage thickness. Three different methods were employed: needle penetration, micro-computed tomography (micro-CT), and histology; the latter was considered the gold standard. Histology and micro-CT scanning results showed no significant differences between thicknesses throughout the condyle. Needle penetration produced significantly higher values than histology, in the lateral and anterior regions. All three methods showed the anterior region to be thinner than the other regions. We concluded that overestimated thickness by the needle penetration is caused by the penetration of the needle through the first layer of subchondral bone, in which mineralization is less than in deeper layers. Micro-CT scanning method was found to be a valid method to quantify the thickness of the cartilage, and has the advantage of being non-destructive. 相似文献
The two major problems that have been reported with the use of polymethylmethacrylate (PMMA) cement are thermal necrosis of surrounding bone due to the high heat generation during polymerisation and chemical necrosis due to unreacted monomer release. Computer models have been used to study the temperature and monomer distribution after cementation. In most of these models, however, polymerisation is modelled as temperature independent and cancellous bone is modelled as a continuum. Such models thus cannot account for the expected important role of the trabecular bone micro-structure. The aim of this study is to investigate the distribution of temperature and monomer leftover at the cancellous bone–cement interface during polymerisation for a realistic trabecular bone—cement micro-structure and realistic temperature-dependent polymerisation kinetics behaviour.
A 3-D computer model of a piece of bovine cancellous bone that underwent pressurization with bone–cement was generated using a micro-computed tomography scanner. This geometry was used as the basis for a finite element model and a temperature-dependent problem for bone cement polymerisation kinetics was solved to simulate the bone cement polymerisation process in the vicinity of the interface. The transient temperature field throughout the interface was calculated, along with the polymerisation fraction distribution in the cement domain.
The calculations revealed that the tips of the bone trabeculae that are embedded in the cement attain temperatures much higher than the average temperature of the bone volume. A small fraction of the bone (10%) is exposed to temperatures exceeding 70°C, but the exposure time to these high temperatures is limited to 50 s. In the region near the bone, the cement polymerisation fraction (about 84%) is less than that in the centre (where it is reaching values of over 96%). An important finding of this study thus is the fact that the bone tissue that is subjected to the highest temperatures is also subjected to high leftover monomer concentration. Furthermore the maximum bone temperature is reached relatively early, when monomer content in the neighbouring cement is still quite high. 相似文献
External and internal head structures of the mantodean Hymenopus coronatus are examined and described in detail. The results are elaborately compared with the literature. Strong crests on the anterior tentorial arms that articulate with the subantennal suture, a parietal suture and glossae and paraglossae with anteriorly bent tips are proposed as new potential apomorphies for Mantodea while a head capsule being wider than long, enlarged compound eyes, the presence of a frontal shield or scutellum, lateral lobes in the anterior tentorial arms, the presence of a transverse and an interantennal suture and the reduction of the mentum are confirmed as apomorphies, As potential apomorphies for Dictyoptera the reduction of Musculus tentoriobuccalis lateralis (M. 49) is newly presented and a “perforate” tentorium, lacinial incisivi that are located in a galeal pouch and the presence of a postmola are confirmed. The present study shows the value of cephalic morphology for phylogenetic analysis but also points out that further studies including evolutionary key taxa are essential for resolving the evolutionary adaptations among dictyopterans. 相似文献
Traditional morphometric approaches for taxonomic assignment of Neanderthal and modern human dental remains are mainly characterized by caliper measurements of tooth crowns. Several studies have recently described differences in dental tissue proportions and enamel thickness between Neanderthal and modern human teeth. At least for the lower second deciduous molar (dm2), a three-dimensional lateral relative enamel thickness index has been proposed for separating the two taxa. This index has the advantage over other measurements of being applicable to worn teeth because it ignores the occlusal aspect of the crown. Nevertheless, a comparative evaluation of traditional crown dimensions and lateral dental tissue proportion measurements for taxonomic assignment of Neanderthal and modern human dm2s has not yet been performed.In this study, we compare various parameters gathered from the lateral aspects of the crown. These parameters include crown diameters, height of the lateral wall of the crown (lateral crown height = LCH), lateral enamel thickness, and dentine volume of the lateral wall, including the volume of the coronal pulp chamber (lateral dentine plus pulp volume = LDPV), in a 3D digital sample of Neanderthal and modern human dm2s to evaluate their utility in separating the two taxa.The LDPV and the LCH allow us to discriminate between Neanderthals and modern humans with 88.5% and 92.3% accuracy, respectively. Though our results confirm that Neanderthal dm2s have lower relative enamel thickness (RET) index compared with modern humans (p = 0.005), only 70% of the specimens were correctly classified on the basis of the RET index. We also emphasize that results of the lateral enamel thickness method depend on the magnitude of the interproximal wear. Accordingly, we suggest using the LCH or the LDPV to discriminate between Neanderthal and modern human dm2s. These parameters are more independent of interproximal wear and loss of lateral enamel. 相似文献
Micron-scale computed tomography (micro-CT) is an essential tool for phenotyping and for elucidating diseases and their therapies. This work is focused on preclinical micro-CT imaging, reviewing relevant principles, technologies, and applications. Commonly, micro-CT provides high-resolution anatomic information, either on its own or in conjunction with lower-resolution functional imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). More recently, however, advanced applications of micro-CT produce functional information by translating clinical applications to model systems (e.g. measuring cardiac functional metrics) and by pioneering new ones (e.g. measuring tumor vascular permeability with nanoparticle contrast agents). The primary limitations of micro-CT imaging are the associated radiation dose and relatively poor soft tissue contrast. We review several image reconstruction strategies based on iterative, statistical, and gradient sparsity regularization, demonstrating that high image quality is achievable with low radiation dose given ever more powerful computational resources. We also review two contrast mechanisms under intense development. The first is spectral contrast for quantitative material discrimination in combination with passive or actively targeted nanoparticle contrast agents. The second is phase contrast which measures refraction in biological tissues for improved contrast and potentially reduced radiation dose relative to standard absorption imaging. These technological advancements promise to develop micro-CT into a commonplace, functional and even molecular imaging modality. 相似文献
Bone quantity and bone quality are important factors in determining the properties and the mechanical functions of bone. This study examined the effects of disrupting bone morphogenetic protein (BMP) signaling through BMP receptors on bone quantity and bone quality. More specifically, we disrupted two BMP receptors, Acvr1 and Bmpr1a, respectively, in Osterix-expressing osteogenic progenitor cells in mice. We examined the structural changes to the femora from 3-month old male and female conditional knockout (cKO) mice using micro-computed tomography (micro-CT) and histology, as well as compositional changes to both cortical and trabecular compartments of bone using Raman spectroscopy. We found that the deletion of Acvr1 and Bmpr1a, respectively, in an osteoblast-specific manner resulted in higher bone mass in the trabecular compartment. Disruption of Bmpr1a resulted in a more significantly increased bone mass in the trabecular compartment. We also found that these cKO mice showed lower mineral-to-matrix ratio, while tissue mineral density was lower in the cortical compartment. Collagen crosslink ratio was higher in both cortical and trabecular compartments of male cKO mice. Our study suggested that BMP signaling in osteoblast mediated by BMP receptors, namely ACVR1 and BMPR1A, is critical in regulating bone quantity and bone quality. 相似文献