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Average displacement of bone fragments for an applied force of 1 kg in patients with mandibular fractures (N = 5 in each group) (91). (a), (b) treated and control patients, respectively.
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In this research, there will be a design driver brushless DC (BLDC), which on the input voltage of the motor driver applying direct current controllers and the implementation mechanism of soft starting the operator of BLDC, which uses fuzzy logic controllers. Testing is done with a view of controlling the application of direct current to the BLDC t...
The following document presents an optimal control technique to control power converters direct current to direct current using the Bang-Bang control technique, for example a Buck power reducing converter will be shown, Subsequently and using an approach based on the principle of the maximum of Pontryagin, an optimized switched control technique (b...
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... 41,42,47,50 However, others have demonstrated osteolysis due to excessive current above only 20 µA. 18,41,52 This speaks to the need to control and carefully specify parameters used in studies. A summary of studies can be found in Table 1. ...
... Alternating current (AC) signals are commonly considered to mimic endogenous signals, but no evidence has shown that an AC signal performs better than a DC signal because it delivers less charge overall. 52 Using equivalent current values but altering signal shape has had greater effect on the amount of bone formation, with results consistently showing that a DC signal is optimal. 10,46-48 A DC signal allows for the highest charge buildup at the cathodic site as well as the most consistent flow of ions, resulting in the greatest formation of bone. ...
... 81 Osteocytes, surrounded by tightly packed collagen fibers, 82 can control bone structure up to 1 µm around the lacuna that they inhabit. 2,52 The matrix directly around the osteocyte does not become fully mineralized, forming the lacuna in which the cell resides to create an interconnected set of canaliculi channels. 83 Osteocytes are presumed to detect and communicate strain when subjected to shear stress by the movement of fluid past their cellular processes. ...
It is hypothesized that bone cells can sense mechanical force in the extracellular network via an electrical signal. This has led to the use of electrical stimulation (ES) to improve fracture repair and mitigate bone loss. Although overlap exists in bone maintenance and fracture healing mechanics, the processes involved in both are very different, resulting in dissimilar behaviors from the cells. Osteocytes are the most abundant cell type in bone tissue, and their basic structure and lineage are fairly well understood, but much debate is present regarding their behavior, with even less known about their behavior in electrical environments. A wide range of research exists on cell behavior under different types of ES, but it is difficult to draw conclusions due to the large variance in stimulation parameters, cell types, and origins (locations and species). By exploring behavior of multiple bone-cell types under different forms of ES, as well as mechanical stimulation through fluid flow, we can determine more about cell reactions to stimuli. In turn, a better understanding of cell response has the potential to improve and broaden therapeutic applications of ES for bone healing and bone loss mitigation, and enhance outcomes for osseointegration into implantable medical devices. These require greater understanding of the bone cellular environment from an electrical perspective as well as cellular responses to ES.
... From a crystallographic point of view, piezoelectricity is a phenomenon of non-centrosymmetric materials [6,8,11,12], such as biological organic systems (biopolymer proteins, polysaccharides, polypeptides, and glands). However, the piezoelectric coefficients of organic materials are generally in the range of 0.1-10 pC/N [6,8,13,14], in contrasts with those of inorganic materials, such as barium titanate (BaTiO 3 ) and lead zirconate titanate (PZT), whose piezoelectric coefficients are between 20 and 800 pC/N [6,7,15]. ...
... Piezoelectricity in bone and collagen was first commented by Fukada and Yasuda in 1957 [18] and has since been observed in different biomaterials including biological tissues such as tendons and teeth [4,[19][20][21][22]. Piezoelectric properties of bone are relevant not only for adaptation and remodeling, but also because external electrical stimulation promotes healing and repair of bone [14,15,17]. ...
Direct and converse piezoelectric effects have been observed in human tooth enamel and dentin. In this study, organic material was removed from dentin and enamel using a chlorinated solution to measure the sole contribution of the inorganic phase. In the direct mode, piezoelectricity is observed when a force applied to the sample produces a voltage. A variable load was applied to the samples with a Shimadzu universal testing machine. In the converse mode, mechanical deformation of the sample occurs under an electric field, which was detected using an atomic force microscope in the piezoelectric mode (piezoresponse force microscope, PFM). For comparison, measurements were also performed on samples where organic (collagen) and inorganic (hydroxyapatite) phases were present. Although a decrease in of the electromechanical response of the organic free sample was observed, the results indicate that the inorganic phase contributes to the piezoelectric property in dentin and in a lesser extent in enamel. This suggests that tooth dentin and enamel apatite nanocrystals present piezoelectric non-centrosymmetric (P63 and P21), as with centrosymmetric (P63/m) structure domains in different percentages.
... Observations of bone's parallel architectural and electrical responses to applied forces have led to suggestions that one or both of the electromechanical signals mediate osteogenesis [20]. In the case of piezoelectricity, the growth of bone could occur in response to the surface polarization itself, or to the subsequent neutralization-ion kinetics [21]. ...
Despite being one of the mostly studied biomaterials for orthopedic, dental, protein purification and stem cell applications, electrical properties of hydroxyapatite has received only limited attention. Since the prediction in 2005 of the possibility of piezo and pyroelectricity in hydroxyapatite several theoretical and experimental works in this field may lead to new understandings of electrical behaviors of calcified tissues in vertebrates. Also, the ability of creating discrete electrostatic domains on nanocrystalline films of hydroxyapatite will open the possibility of understanding how surface charge influences biological interactions. The outlook for future endeavours in this field will be discussed.
... 21 Observations of bone's parallel architectural and electrical responses to applied forces have led to suggestions that stress generated potentials (piezoelectricity and streaming potential) mediate osteogenesis. 22 In the case of piezoelectricity, the growth of bone could occur in response to the surface polarization itself, or to the subsequent neutralization-ion kinetics. 23 With the data at hand for maximum macroscopic longitudinal piezoelectricity 2.5 pC/N from the current investigation and the longitudinal modulus of elasticity measured as 91.28 GPa by using ultrasound on ceramic HAp in a previous study, 19 we obtain a charge constant of 22.5 lC/cm 2 . ...
Direct current electrical poling of textured hydroxyapatite (HAp) ceramics is reported here to exhibit weak ferroelectricity and pyroelectricity, but a remarkably higher (six orders of magnitude) piezoelectricity. The piezoelectric strain coefficient is an order higher than that of bone and of the same order as that of quartz crystal and uncalcified collagen in tendon. The piezoelectric charge coefficient is an order higher than bone, and three orders higher than that of tendon. Piezoelectric constants of poled HAp ceramics are high enough to have physiological relevance such as in the use of bone grafts for stimulated calcification or in energy harvesting from physiological motions. Piezoelectricity in these ceramics can be tuned by controlling texture, and poling parameters. The density of power that can be harvested from HAp ceramics is currently just one order lower than biocompatible ferroelectric ceramic such as barium titanate.
... A mixture of autogenous cancellous bone and HA may result in bone growth in regions that would otherwise be filled with connective tissue. 5 Because electrical stimulation can also promote osteogenesis, 9 we studied the possibility that such stimulation could function as a substitute for autogenous bone in promoting bone growth around HA particles. To facilitate the study of electrically stimulated bone (in distinction to trauma-induced reparative bone growth), a model was developed that did not involve an osseous defect. ...
... Based on this observation, and on an analysis of the pertinent literature, a model of electrically stimulated osteogenesis was proposed in which the stimulus results in an acute inflammatory response having one or more components that are mitogenic for osteoprogenitor cells. 9 The osteoprogenitor cells then proliferate, differentiate, and form the osteoblasts responsible for the stimulated growth. ...
... The range of electrical current that produces osteogenesis is relatively narrow and model dependent. 9 Osteonecrosis rather than osteogenesis occurs if the current is too high. Perhaps the current employed in this study was too high for the uninjured mandible, and resulted in bone necrosis during the first postoperative week. ...
Nonresorbable, nonporous, particulate hydroxyapatite (HA) was implanted on the mandible in rabbits and stimulated electrically, 4 hours per day, during the first postoperative week. Stimulated and control implant sites were recovered 8 weeks postoperatively and examined histologically. The HA migrated into the mandible in the electrically treated specimens, and was routinely found in intimate association with preexisting mandibular bone. In the controls, the HA remained superior to the mandibular surface. In further studies (without electrical stimulation) in which the implant site was recovered 26 weeks postoperatively, HA was observed in the mandible; some HA particles migrated completely through the mandible and were found in the adjacent soft tissue. It was concluded that, under the conditions studied, electrical stimulation does not promote bone growth into HA, but rather produces the opposite result--it promotes more rapid movement of HA particles into the mandibular bone. The HA particle migration into the mandible observed (longer postoperative times) in the absence of electrical stimulation suggests that migration is a general property of HA particles when placed over bone under muscle.
... The tooth itself does not exhibit a growth response because its piezoelectric effect is weak (or absent, as in the case of enamel). Based on detailed stress-charge measurements (McElhaney, 1967), a similar hypothesis has been proposed for modelling of the long bones (Marino, 1988). Thus piezoelectricity is a possible mechanism to explain alveolar remodelling. ...
... Electromechanical signals have been recorded from mineralized tissue for more than 30 years, and both their origin and physiological role have been the subject of extensive discussion. It is now clear that, in physiologically moist tissue, the measured voltages arise from the motion of ions near the tissue surface-a phenomenon known as streaming potentials (Marino, 1988). Voltages of piezoelectric origin, in contrast, are not normally measured in wet tissue (because the developing piezoelectric polarization is neutralized by the motion of ions in the bulk fluid). ...
... It is important to recognize that piezoelectric polarization and concomitant neutralization kinetics actually exist at the cellular level in physiologically moist tissue (and hence can serve as a cell stimulus), even though they are not normally measured over the macroscopic dimensions of wick or metal-foil electrodes. The evidence suggesting a physiological role for piezoelectricity is indirect (Marino, 1988;Marino et al., 1988), and it is generally unimpressive except in comparison to the data supporting the alternative. There is no real evidence that streaming potentials have a physiological role-interest in that phenomenon can be traced primarily to the fact that it is easily measured. ...
Unlike the dental hard tissues, bone remodels when subjected to orthodontic forces. Bone is also piezoelectric (generates a surface electrical charge upon application of force). In dentine and cementum from sperm whale teeth (which gave samples of sufficient size), the existence and magnitude of piezoelectricity were examined and compared with human bone. Both dental tissues were found to be piezoelectric with coefficients of 0.027 and 0.028 pC/N, respectively; the coefficient of human bone was eight times greater (0.22 pC/N). Thus the strength of the piezoelectric effect was correlated with the known capacities of the tissues to undergo adaptive remodelling. This result is consistent with the theory that piezoelectricity mediates orthodontically induced alveolar remodelling.
... Streaming potentials arise from kinetic modification of the electrical potential at the slip plane [2], and piezoelectric polarization occurs as a consequence of rotation of peptide-bond dipoles [3]. Streaming potentials are the physical basis of the electrical signals observed in bone, tendon, and cartilage subjected to mechanical forces under physiological conditions [4]. The piezoelectric signal is not usually measured under such conditions because the induced polarization is rapidly neutralized by ions in the bulk fluid. ...
... When an intact human femur was subjected to a simulated physiological load, the average of the absolute value of 145 measurements of the polarization was 7 pC/cm 2 (range, 0.3-30 pC/cm 2 ) [12]. The magnitude and sign of the measured charge densities were theoretically correlated with a self-consistent change in the outline of the bone [4]. Thus the occurrence of an osteogenic response associated with 90 pC/cm 2 is in good agreement with the interpretation of direct measurements of the polarization produced in bone. ...
Bones respond to mechanical forces by modifying their architecture. Mechanical forces also result in at least two electromechanical signals in bone — streaming potentials and piezoelectric polarization. Observations of bone's parallel architectural and electrical responses to forces have led to suggestions that one or both of the signals mediate the osteogenic response by directly triggering bone-cell activity. This study was undertaken to determine whether piezoelectric polarization could alter bone-cell physiological function.Piezoelectric and non-piezoelectric forms of the polymer polyvinylidene fluoride were implanted in rats, and the effect on periosteum and bone was studied histologically. More bone formation and periosteal reaction occured in association with the piezoelectric form of polyvinylidene fluoride. The effects were statistically significant at 1–6 and 1–2 weeks postoperatively for bone and periosteum, respectively. Nether mechanical nor chemical factors could account for the results, which therefore must have been due to the quasi-static piezoelectric polarization (about 90 pC/cm2). The osteoprogenitor cell but not the mesenchymal cell (its less differentiated precursor) was capable of responding to the polarization.
The speedup of numerical computation of boundary value problem is possible to achieve on several levels. Firstly, the iterative solver is parallelized, and secondly, the suitable methods like conjugated gradient and multigrid are applied. Various aspects of the FD method - including boundary conditions, mesh band structure and computing speedup - are described in detail. This paper emphasis on the parallelization of the FD method. The parallelization of the boundary value problem depends on the computer hardware. This can be organized as shared or distributed memory system. We also considered the possibilities of the parallel virtual machine (PVM). Therapeutic and functional electrical stimulation are acknowledged methods for improving the rehabilitation of the patients with neuromuscular problems. Electric field is used in cancer treatment, bone growth, wound healing and nerve regeneration. In order to analyze the current field density distribution a large-scale finite difference (FD) three-dimensional model of biological tissues around a sacrum bedsore in humans has been calculated by means of numerical solution of Laplacean partial differential equation. Non-homogeneous and anisotropic electric properties of living tissue have been considered in all models. A uniform mesh was applied. Parallel numerical algorithms have been implemented in two different computer architectures. The first one is a shared-memory Silicon Graphics PowerChallenge and the second one is a distributed memory Transputer system. The convergence of the Gauss-Seidl iterative method was analyzed theoretically and the number of required iterations for given numerical accuracy has been estimated (eqn. 5). Convergence was improved by using multigrid method. The questions are the rates of speedup of numerical solutions due to parallel algorithms, and comparison of effectiveness between two architectures. On the computer system based on the shared memory architecture the optimal number of parallel processors has been estimated for the given model size (fig. 8). Numerical experiments on various computer architectures show that speedup significantly depends on the scale of the model. Greater speedup is achieved in the case of larger number of mesh points - unknowns, up to the 512000. The most effective calculations of the electric fields distribution are obtained by 16 processors shared memory PowerChallenge. On the other hand Transputer based architecture with distributed memory makes possible to implement scalable parallel algorithms suitable for large number of processors. It was estimated, on the basis of numerical experiment, that optimal number of processors in case of shared memory architecture is about 48 processors within PowerChallenge computer system. One can conclude that for this particular problem in case of biological system the basic mesh size of 5 mm is not fine enough. The 3D model needs to be consisted of several millions of mesh points. Algorithms and platforms used in this numerical experiments do not guarantee a satisfactory solution at present.
A finite difference (FD) three-dimensional (3D) model of biological tissue around a sacrum bedsore in humans has been developed. The electric field due to externally applied electrical stimulation has been calculated by means of the numerical solution of the laplacean partial differential equation. A non-uniform mesh was applied and a parallel numerical algorithm was proposed in order to speed up the solution. Non-homogeneous and anisotrophic electric properties of living tissues were considered. Two FD models with two different sizes of bipolar external electrodes were compared in order to increase the electric field strength in the target tissue near the sacral wound. The proposed large-scale 3D model and FD method were found to be an effective tool for analysis of electric field distribution inside biological tissues. The numerical results were compared with those reported in the literature about extremely low-frequency electromagnetic fields near power transmission lines, the electromagnetic fields used in clinical practice. They were all reviewed in relation to relevant references.
