Дисертації: "Human dental tissues"

1

Abdullah, Ahmed. "In vitro and in situ studies to investigate the erosion of human dental tissues." Thesis, University of Leeds, 2009. http://etheses.whiterose.ac.uk/11292/.

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2

Sui, Tan. "Thermal-mechanical behaviour of the hierarchical structure of human dental tissue." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2c8e9604-ec4b-4cfa-b6df-fff3e6579492.

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Human dental tissues are fascinating nano-structured hierarchical materials that combine organic and mineral phases in an intricate and ingenious way to obtain remarkable combinations of mechanical strength, thermal endurance, wear resistance and chemical stability. Attempts to imitate and emulate this performance have been made since time immemorial, in order to provide replacement (e.g. in dental prosthodontics) or to develop artificial materials with similar characteristics (e.g. light armour). The key objectives of the present project are to understand the structure-property relationships that underlie the integrity of natural materials, human dental tissues in particular, and the multi-scale architecture of mineralized tissues and its evolution under thermal treatment and mechanical loading. The final objective is to derive ideas for designing and manufacturing novel artificial materials serving biomimetic purposes. The objectives are achieved using the combination of a range of characterization techniques, with particular attention paid to the synchrotron X-ray scattering (Small- and Wide-Angle X-ray Scattering, SAXS and WAXS) and imaging techniques (Micro Computed Tomography), as well as microscopy techniques such as Environmental Scanning Electron Microscopy (ESEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). Mechanical properties were characterized by nanoindentation and photoelasticity; and thermal analysis was carried out via thermogravimetric analysis (TGA). Experimental observations were critically examined and matched by advanced numerical simulation of the tissue under thermal-mechanical loading. SAXS and WAXS provided the initial basis for elucidating the structure-property relationships in human dentine and enamel through in situ experimentation. Four principal types of experiment were used to examine the thermal and mechanical behaviour of the hierarchical structure of human dental tissue and contributed to the Chapters of this thesis: (i) In situ elastic strain evolution under loading within the hydroxyapatite (HAp) in both dentine and enamel. An improved multi-scale Eshelby inclusion model was proposed taking into account the two-level hierarchical structure, and was validated against the experimental strain evaluation data. The achieved agreement indicates that the multi-scale model accurately reflects the structural arrangement of human dental tissue and its response to applied forces. (ii) The morphology of the dentine-enamel junction (DEJ) was examined by a range of techniques, including X-ray imaging and diffraction. The transition of mechanical properties across the DEJ was evaluated by the high resolution mapping and in situ compression measurement, followed by a brief description of the thermal behaviour of DEJ. The results show that DEJ is a narrow band of material with graded structure and mechanical properties, rather than a discrete interface. (iii) Further investigation regarding the thermo-mechanical structure-property relationships in human dental tissues was carried out by nanoindentation mapping of the nano-mechanical properties in ex situ thermally treated dental tissues. (iv) In order to understand the details of the thermal behaviour, in situ heat treatment was carried out on both human dental tissues and synthetic HAp crystallites. For the first time the in situ ultrastructural alteration of natural and synthetic HAp crystallites was captured in these experiments. The results presented in this thesis contribute to the fundamental understanding of the structure-property integrity mechanisms of natural materials, human dental tissues in particular. These results were reported in several first author publications in peer-reviewed journals, conference proceedings, and a book chapter.

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3

Montgomery, Janet. "Lead and strontium isotope compositions of human dental tissues as an indicator of ancient exposure and population dynamics." Thesis, University of Bradford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527341.

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Abstract: This thesis employs lead and strontium isotope analysis of teeth by TIMS to identify migrants amongst British archaeological cemetery populations since the Neolithic. The study evaluates the benefits of combining two independent isotope systems with the exposure information obtained from elemental concentrations of lead and strontium. It demonstrates that they provide complementary information about mobility but highlights how their efficacy fluctuates both spatially and temporally in the periods investigated. Strontium was useful in all periods but heavily biased towards maritime 87Sr/86Sr (~O.7092) making it a poor discriminant between coastal habitats where lead was superior. Lead utility changes following the advent of large-scale mining and metallurgy, when anthropogenic ore lead severs the link between geographical origin and lead exposure. A cultural focussing of British enamel signatures ensues accompanied by a concomitant rise in lead burdens. British lead exposure during the last two millennia appears more indicative of status and the cultural sphere (e.g. rural/urban) than geographical origin. The results are assessed in the light of migration theory and traditional archaeological and osteological indicators. Samples used are core enamel and co-genetic primary crown dentine, which neither model nor remodel in vivo and thus remain representative of a constrained period of childhood. Modem and archaeological teeth are investigated to assess isotope variability intra-enamel, intra-tissue, intra-antimere, intra-dentition, intra-sibling and between mother/child pairs. Recommendations for future tissue sampling and standardisation are made. The fundamentals of tooth biomineralisation are reviewed and clarified, chiefly that incremental enamel structures relate to initial formation not mineralisation; lead and strontium are principally incorporated during mineralisation. Macromorphological preservation proved no guide to biogenic strontium or lead isotope integrity. Mature, but not immature, enamel proved highly resistant to diagenesis whether well preserved or not. Dentine was highly susceptible to diagenesis irrespective of preservation state and is proposed as a proxy for the time averaged isotope signature of the soil. Moreover, it is argued that lead and strontium behave differently in teeth; uptake mechanisms are different and they respond independently to subsequent migration. Results suggest soil leaches were useful but complex and the most suitable leach reagent may be specific to the soil type and isotope system. Two Norse Period immigrants (male and female) were identified at Cnip, Lewis; the the 87Sr/86Sr signatures constrain their origin to Tertiary volcanics. In the North Atlantic these occur on Iceland, Faeroe Isles, and Antrim in Ireland but not Norway. No indubitable immigrants were identified at the Anglian cemetery at West Heslerton, Yorkshire but soil leaches and juveniles suggested a local 87 Sr/86Sr signature range. "Non-locals" included both sexes, weapon burials and unaccompanied burials, providing no evidence for an immigrant group composed solely of male warriors. All analysed burials with wristclasps and cruciform brooches were non-local, supporting Hines' (1984) hypothesis that wristclasps confirm the presence of Norwegian immigrants during this period.

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4

Al-Hazaimeh, Nawaf Ismail. "Revascularization of human dental pulp using tissue engineering approaches." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582741.

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Advancement in stem cell technology allows for many therapeutic opportunities, including the treatment of previously intractable conditions. Revascularization of dental pulp tissue, and specifically angiogenic differentiation of Human Dental Pulp Stem Cells, is of great interest due to the crucial role of this process not only in dental pulp regeneration, but also in wound healing and in regenerative medicine in general. One of the challenges of tissue engineering is the ability to provide sufficient blood supply for engineered tissue and organs in the first phase after transplantation. The present study investigated the potential use of HDPSCs in revascularization of dental pulp in vitro as well as in vivo using Matrigel basement membrane as 3D scaffold and compared this data to that of stem cells isolated from dental pulp tissue using the stem cell marker Stro-1. Initially these cells were cultured under angiogenic condition (EGM-2) for cell differentiation and treated with VEGF. The angiogenic potential of human dental pulp stromal/stem cells was investigated at gene and protein level by qRT-PCR and immunohistochemical analysis of appropriate angiogenic markers. Moreover we monitored the differentiation of these cells by confocal and light microscopy. In the second part of the present study we investigated the ability of these cells to differentiate and form vascular tissue in an appropriate animal model. Two in vivo models were used; HDPSCs or Stro-1 +CD45- cells were suspended in Matrigel and injected into the root canal space of human tooth sections and implanted subcutaneously into immunocompromised mice for 3 weeks. The other model was the Matrigel plug assay, which is widely used for angiogenesis studies. qRT-PCR and Immunohistochemistry studies indicated that CD31 and VEGFR-2 were upregulated in HDPSCs and stro-t- CD45- cells in monolayer cultures, and all angiogenic markers (CD31, CD34, vWF, and VEGFR-2) in Matrigel cultures were upregulated as well following treatment with VEGF in endothelial cells growth medium-2. In 3D Matrigel culture, cells were also able to form tube like network structures. These results were confirmed by in vivo study, in which we were able to regenerate vascular like tissue which contained red blood cells in both in vivo models. This data indicated that these vessels are functional when compared to normal vascular tissue in both human and mice. In conclusion, the present study confirmed that HDPSCs and Stro-1 +CD45- cells were induced to express angiogenic markers in vitro and can be recruited in the formation of vascular tissue in a tooth section as well as Matrigel plug constructs in immunocompromised mice. This technique can be used in the future to revascularize dental pulp which will enhance the survival rate of traumatized teeth.

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5

Feeney, Robin N. M. "MICROTOMOGRAPHIC ANALYSIS OF SEXUAL DIMORPHISM AND DENTAL TISSUE DISTRIBUTION IN HUMAN MOLARS." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250270343.

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6

Rizk, Ahmed El Sayed Mahmoud. "Human dental pulp stem cells expressing TGF{221}-3 transgene for cartilage-like tissue engineering." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47752890.

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A major challenge facing the tissue engineering discipline is cartilage tissue repair and engineering, because of the highly specialized structure and limited repair capacity that cartilage possesses. Dental pulp stem cells (DPSCs) were identified about a decade ago as a potential candidate for cell based therapy and tissue engineering applications. The present study aimed to utilize gene therapy with isolated DPSCs to induce chondrogenic transgene expression and chondrogenic lineage differentiation, with the ultimate goal of engineering cartilage tissue-like constructs. We isolated DPSCs from human teeth extracted for orthodontic treatment. We further enriched the isolated population using immunomagnetic bead selection, which increased stem cell markers: Stro-1 and CD146, compared to unselected population. The DPSCs showed the ability to differentiate into the chondrogenic lineage when induced with recombinant hTGFβ-3 and when transduced with hTGFβ-3 transgene. We successfully constructed the recombinant adeno-associated viral vector encoding the human TGFβ-3, and determined the best multiplicity of infection for DPSCs. The transduced DPSCs highly expressed hTGFβ-3 for up to 60 days. Expression of chondrogenic markers; Collagen IIa1, Sox9, and aggrecan was verified by immunohistochemistry and mRNA. We successfully fabricated an electrospun nano-fiber scaffold upon which morphology, proliferation and viability of the DPSCs were examined. DPSCs attached and proliferated on nano-fiber scaffolds demonstrating better viability compared to micro-fiber scaffolds. Transduced cells expressed hTGFβ-3 protein up to 48 days. Cells seeded on nanofiber scaffolds showed higher expression levels compared to micro-fiber scaffolds or culture plate. Scaffolds seeded with DPSCs were implanted in nude mice. Immunohistochemistry for TGFβ-3 DPSCs constructs (n=5/group) showed cartilage-like matrix formation with glucoseaminoglycans as shown by Alcian blue. Immunostaining showed positivity for Collagen IIa1, Sox9 and aggrecan. Semi-thin sections of the transduced DPSCs constructs examined by transmission electron microscopy (TEM) showed chondrocytic cellular and intra-cellular features, as well as extracellular matrix formation (n=2/group). In vivo constructs with the TGFβ-3 DPSCs showed higher collagen type II and Sox9 mRNA expression relative to non-transduced DPSCs constructs (n=5/group). Western blot analysis confirmed this expression pattern on the protein level (n=3/group). Engineered constructs mechanical properties were examined and compared to patellar bovine cartilage to assess functionality (n=5/group). TGFβ-3 transduced DPSCs constructs showed a higher equilibrium elastic modulus compared to nontransduced constructs. Micro-fiber scaffolds constructs showed a higher elastic modulus (0.11 MPa, 18% of bovine cartilage), compared to nano-fiber constructs modulus (0.032 MPa, 6% of bovine cartilage). Nano-fiber based constructs showed a similar Poisson‘s ration to bovine cartilage, while that of micro-fiber scaffolds was lower. As an alternative gene delivery method, electroporation parameters for DPSCs transfection were optimized, and compared to commonly used chemical transfection methods. TGFβ-3 transfected DPSCs showed a significantly higher relative TGFβ-3 mRNA and protein expression compared to non transfected control and to eGFP transfected DPSCs. Transfected DPSCs showed increased relative expression of chondrogenic markers; Collagen II, Sox9 and aggrecan, compared to non transfected DPSCs. Successful chondrogenic differentiation of DPSCs gene therapy with TGFβ-3 transgene, and seeding them on PLLA/PGA scaffolds makes it a potential candidate for cartilage tissue engineering and cell based therapy.
published_or_final_version
Dentistry
Doctoral
Doctor of Philosophy

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7

Moretti, Rani da Cunha [UNIFESP]. "Medicação pré-operatória dexametasona – os efeitos na cultura primária de células de polpa dental humana." Universidade Federal de São Paulo (UNIFESP), 2015. http://repositorio.unifesp.br/handle/11600/39323.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Rede Ibero-Americana de Biofabricação
Introdução: A aplicação de dexametasona em cultura de células mesenquimais induz diferenciação osteoblástica, consequentemente formação de tecidos mineralizados. A Engenharia Tecidual propõe o desenvolvimento de estratégias terapêuticas direcionadas à regeneração funcional e estrutural de tecidos biológicos. Nesse sentido, a caracterização celular in vitro é fundamental para garantir o desenvolvimento destas técnicas. Objetivo: Avaliar o efeito da dexametasona administrada como medicação pré-operatória na cultura de células primárias de polpa dental humana. Métodos: Foram utilizadas células provenientes da polpa de terceiros molares. Essas foram distribuídas em dois grupos experimentais com dois protocolos de medicação pré-operatória utilizados em rotina odontológica, onde no protocolo B, o paciente ingeria 1 comprimido de dexametasona 1hora antes à cirurgia e no A não. A avaliação da proliferação, viabilidade e diferenciação, foram pelos testes Trypan Blue, MTT, Von Kossa e Alizarin Red respectivamente, e realizadas em intervalos fixados. Análise de variância de Friedman e t test foram aplicados, fixando em 95% de confiança. Resultados: As células pertencentes ao protocolo A atingiram pico de proliferação aos 21 dias de cultura enquanto as células do protocolo B em 14. Células do protocolo A foram estatisticamente mais viáveis aos 7 e 21 dias enquanto as do protocolo B, aos 14. Na análise de Von Kossa e Alizarin Red observou-se que as células pertencentes ao protocolo B formaram nódulos de calcificação desde 7 dias de cultura enquanto no A aos 14. Conclusão: A utilização da dexametasona como medicação pré-operatória em cirurgia de terceiros molares promove diferenciação celular precocemente, quando observada in vitro.
Introduction: The use of dexamethasone in mesenchymal cell culture induces osteoblastic differentiation and, consequently, formation of mineralized tissues. Tissue Engineering proposes the development of therapeutic strategies aiming at structural and functional regeneration of biological tissues. In this sense, cell characterization in vitro is critical to ensure the development of such techniques. Objective: To evaluate the effect of dexamethasone administered as preoperative medication in primary cell culture of human dental pulp. Methods: We used cells from the third molar pulp. These cells were divided into two experimental groups, each with two preoperative medication protocols used in dental routine and differentiated by the intake of dexamethasone in one of them. The assessment of proliferation, differentiation, and viability through Trypan Blue, MTT and von Kossa, and Alizarin Red tests, respectively, were held in fixed intervals. Friedman analysis of variance and t test were applied, and confidence interval was set at 95%. Results: Protocol A cells proliferation reached its peak on day 21 while protocol B cells proliferation reached its peak on day 14. Protocol A cells were statistically more viable between days 7 and 21 whereas protocol B cells viability was higher on day 14. Von Kossa and Alizarin Red analyses showed that calcified nodules formation occurred from the seventh day of cell culture in protocol B cells and on day 14 in protocol A cells. Conclusion: The use of dexamethasone as preoperative medication in third molar surgery promotes cell differentiation earlier, when observed in vitro.
FAPESP: 07/51227-4
FAPESP: 08/57860-3
CNPq: 573661/2008-1

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8

Pääkkönen, V. (Virve). "Expression profiling of human pulp tissue and odontoblasts in vivo and in vitro." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514290053.

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Abstract Dentin forms the hard tissue portion of the dentin-pulp complex, while the dental pulp is soft connective tissue that retains the vitality of the dentin. Odontoblasts form the outermost cell layer of pulp and play a central role during dentin formation by producing and mineralizing the dentin matrix. The understanding of the defensive reactions in the dentin-pulp complex is limited. Information about the transcriptome and proteome of pulp tissue and odontoblasts would facilitate understanding of their functions during health and disease. The aim of this study was to investigate the expression profiles of human pulp tissue and odontoblasts in vivo and in vitro using large-scale expression analysis methods. Also, the suitability of these methods in pulp biological research in vivo and in vitro was evaluated. cDNA microarray revealed only minor variation and 2-D electrophoresis combined with mass spectrometry revealed no differences between healthy and carious teeth pulp tissue in vivo. The effect of transforming growth factor β1 (TGF-β1) on pulp and odontoblasts was studied in vitro using oligonucleotide-based microarrays, and marked changes in the transcriptome were revealed, especially in the expression of chemokine- and cytokine-related genes. Transiently increased interleukin expression was confirmed at the protein level by antibody array. DNA microarray analysis of native pulp tissue and odontoblasts was used to search for potential odontoblast markers. Only one gene related to extracellular matrix organization and biogenesis, matrilin 4, and two expressed sequence tags (ESTs), which represent transcribed sequences encoding possibly unknown genes, were identified in odontoblasts but not in pulp. Analysis of mature native odontoblasts and cultured odontoblast-like cells by DNA microarray revealed a high similarity (84%) between native and cultured cells. Also, differential expression levels of selected neuronal proteins were observed and confirmed at the mRNA and protein levels. In conclusion, microarray is a powerful tool for pulp biology, especially for in vitro studies. TGF-β1 was revealed as a potent regulator of proinflammatory responses in the dentin–pulp complex. In addition, several potential odontoblast markers were identified by microarray, and the similarity of cultured odontoblast-like cells used in the study with native odontoblasts was confirmed.

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9

Moharamzadeh, Keyvan. "Development of a tissue engineered human oral mucosal model for the assessment of the biocompatibility of resin-based dental materials." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485086.

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Restorative materials and oral health care products come into direct contact with oral mucosa. Components of dental composite resins can be released into the oral cavity and can cause adverse reactions. To obtain an accurate risk assessment, the in vitro test model must reflect the clinical situation as closely as possible. Therefore, the aim of this study was to develop a three-dimensional tissue engineered human oral mucosal model to assess the biocompatibility of resin-based dental materials. In this study in vitro biocompatibility of resin-based dental materials was assessed using a variety of laboratory techniques including cytotoxicity tests on different monolayer cultures of epithelial cells, chemical analysis of components released. from different composite resin systems, and finally a tissue-engineered human oral mucosal model was developed, characterised and examined for biological assessment of resin-based dental materials. The results showed that dental resin monomers were toxic to the epithelial cells and the monomer TEGDMA was the major component released from composite reins in quantifiable amounts and may be sufficient to cause an adverse reaction. The type of extraction media and the time of analysis had a significant effect on the detection of monomer released from composite resins due to protein binding. A welldifferentiated and highly reproducible full-thickness oral mucosal model was developed and characterised that has the potential to be used for mucotoxicity and biocompatibility assessment of dental materials. Exposure to high-TEGDMA containing composite resins caused a significant mucotoxicity and increased the amount of IL-I J3 released from the oral mucosal model. The 3-D tissue engineered human oral mucosal model is believed to be more clinically relevant than monolayer culture of epithelial cells and the results obtained from multiple-endpoint analysis of the oral mucosal model were more coherent.

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10

Terada, Andrea Sayuri Silveira Dias. "Utilização do produto Allprotect Tissue Reagent® na estabilização do DNA extraído de tecidos dentais humanos em diferentes condições de armazenamento." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/58/58137/tde-17052013-110504/.

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A metodologia genético-molecular destaca-se como uma técnica apurada para os processos de identificação humana e, dentre as fontes de evidência biológica, o uso de elementos dentais é de grande interesse. A manutenção da integridade do material enviado ao laboratório é imprescindível para o sucesso dos resultados obtidos e uma das principais dificuldades encontradas é com relação ao armazenamento da amostra, que geralmente é realizado em baixas temperaturas. O presente trabalho avaliou a eficácia do produto Allprotect Tissue Reagent® (Qiagen, Hilden, Germany) na estabilização do DNA extraído de tecidos dentais humanos armazenados em diferentes condições. Para tal, foram utilizados 165 elementos dentais, os quais foram distribuídos em dois grupos distintos: dente íntegro e tecido pulpar dental isolado. As amostras foram armazenadas com ou sem a utilização do referido produto, variando o período de tempo (1, 7, 30 e 180 dias) e temperatura (ambiente e refrigeração). Além desses grupos, foi formado um grupo controle positivo composto por cinco elementos dentais armazenados a -20ºC durante 180 dias. Após o armazenamento foi realizada extração do DNA, eletroforese em gel de agarose, quantificação do DNA genômico por PCR Tempo Real e análise de fragmentos de 37 amostras. Os fragmentos de 32 amostras que representavam cada condição possível e as cinco amostras do grupo controle positivo foram analisados, a fim de verificar quatro marcadores pré-selecionados. O gel de agarose mostrou evidências da presença de DNA genômico. Os valores da quantificação foram analisados estatisticamente pelos testes Kruscal-Wallis e Mann-Whitney. Os resultados mostraram valores que variaram de 0,01 a 10246,88ng/L de DNA. Houve diminuição da concentração de DNA nas amostras de dente armazenadas em temperatura ambiente por 30 e 180 dias em relação às que ficaram armazenadas por 1 e 7 dias. Além do fator tempo, a temperatura também influenciou na concentração de DNA, sendo maior nos dentes que ficaram por 30 dias e na polpa dental mantida por 180 dias, quando refrigerados. Em relação à utilização do produto Allprotect Tissue Reagent® (Qiagen, Hilden, Germany), o mesmo mostrou diferença significativa na estabilização dos dentes que foram armazenados em temperatura ambiente durante 30 e 180 dias. A análise de fragmentos foi possível nas 37 amostras selecionadas, independente da quantidade de DNA, confirmando a importância das reações de amplificação e da análise de STR utilizando método automático. Conclui-se que a utilização do produto Allprotect Tissue Reagent® (Qiagen, Hilden, Germany) mostrou diferença significativa na estabilização do DNA das amostras de dentes íntegros armazenadas em temperatura ambiente durante 30 e 180 dias, enquanto que nas demais condições testadas, os resultados não evidenciaram justificativas para o uso do produto.
The genetic-molecular methodology stands out as an accurate technique for human identification process and among the sources of biological evidence, the use of teeth is of great interest in Forensic Dentistry. Maintaining integrity of the material sent to laboratory is essential for success of the analysis, and one of the main difficulties is related to sample storage, which is usually carried out at low temperatures. This study evaluated the effectiveness of the Allprotect Tissue Reagent® (Qiagen, Hilden, Germany) in stabilizing DNA extracted from human dental tissues stored under different conditions. In this study were used 165 teeth, distributed in two groups: intact teeth and isolated pulp tissue. The samples were stored with or without the product and varying the storage time (1, 7, 30 and 180 days) and temperature (room temperature and under refrigeration). In addition to these groups, was formed a positive control group, composed by five teeth, which was stored at -20ºC for 180 days. After storage, DNA extraction, electrophoresis on agarose gel and genomic DNA quantification by Real-Time PCR and fragments of 37 samples were performed. The fragments of 32 samples representing every possible condition and five positive control group samples were analyzed to verify four pre-selected markers. The agarose gel showed evidences of genomic DNA presence. Quantification results were statistically analyzed with the tests Kruscal-Wallis and Mann-Whitney. Quantification results showed values ranging from 0.01 to 10,246.88 ng/L of DNA. There was a decrease in DNA concentration in stored tooth samples at room temperature for 30 and 180 days compared to those stored for 1 and 7 days. Besides the time factor, temperature also influenced the DNA concentration, being higher in teeth that remained for 30 days and in tooth pulp maintained for 180 days, under refrigeration. Regarding the use of Allprotect Tissue Reagent® (Qiagen, Hilden, Germany) it showed a significant difference in stabilization of stored teeth at room temperature for 30 and 180 days. The analysis of fragments was possible in 37 selected samples, regardless of the DNA quantity variation, confirming that amplification reactions and STR analysis using automated methods provides good results. It was concluded that the use of Allprotect Tissue Reagent® (Qiagen, Hilden, Germany) showed a significant difference in stabilizing DNA samples of intact human teeth stored at room temperature for 30 and 180 days, while in the other test conditions the results showed no justification for using this product.

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11

Zimmerman, Heather. "Preliminary Validation of Handheld X-Ray Fluorescence (HHXRF) Spectrometry: Distinguishing Osseous and Dental Tissue from Non-Bone Material of Similar Chemical Composition." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5895.

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Forensic anthropologists normally examine bone from a variety of medicolegal contexts. The skeletal remains may in some cases be highly fragmented or taphonomically modified, making it difficult to sort bone from non-bone material. In these cases, the forensic anthropologist may rely on microscopic or destructive chemical analyses to sort the material. However, these techniques are costly and time-intensive, prompting the use of nondestructive analytical methods in distinguishing bone and teeth from non-bone materials in a limited number of cases. The proposed analytical techniques are limited in that they rely on an examination of the major elements in the material, and do not sort out all materials with a similar chemical composition to bone/teeth. To date, no methods have been proposed for the use of handheld X-ray fluorescence (HHXRF) spectrometry in discriminating human and nonhuman bone/teeth from non-bone materials. The purpose of this research was to develop a method for the use of HHXRF spectrometry in forensic anthropology specifically related to distinguishing human and nonhuman bone and teeth from non-bone materials of a similar chemical composition using multivariate statistical analyses: principal components analysis (PCA), linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), and hierarchical cluster analysis (HCA). This was accomplished in two phases. Phase 1 consisted of a Reliability Test and involved sampling a single human long bone in thirty locations. Multiple spectra were collected at each location to examine the reliability of the instrument in detecting the elements both within a single site and between multiple sites. The results of the Reliability Test indicated that HHXRF consistently detected the major and minor elements found on the surface of a human bone. These results were used for Phase 2, designated the Accuracy Test, which involved analyzing a set of materials compiled from the literature to test the accuracy of the technique in discriminating bone (human and nonhuman) and non-bone samples (other biological and non-biological). The results of the Accuracy Test indicate that osseous and dental tissue can be distinguished from non-bone material of similar chemical composition with a high degree of accuracy (94%) when data is collected from several locations on a sample and analyzed separately during multivariate statistical analyses. Overall, it was not possible to discriminate rock apatite and synthetic hydroxyapatite (synthetic bone) from bone. However, this technique successfully discriminated other non-bone materials that are chemically similar to bone, such as ivory and octocoral, which previous methods focusing on only a comparison of Ca/P ratios were unable to distinguish from bone.
M.A.
Masters
Anthropology
Sciences
Anthropology

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12

Vernon, Lauren Louise. "A Comparison of the Osteogenic Tissue Engineering Potential of Dental-Derived Stem Cell Lines: Stem Cells from Human Exfoliated Deciduous Teeth (SHEDs) vs. Periodontal Ligament Stem Cells (PERIOS)." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/19.

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The goal of this study is to assess the osteogenic potential of two types of dental stem cell lines within a tissue engineering application. More specifically, the goal of this study is to find a readily abundant cell source with capacity to express an osteogenic phenotype. There are two parameters utilized to evaluate tissue engineering potential of cells: proliferation rate and differentiation potential. Briefly, proliferation rate is the speed at which cells divide and differentiation potential determines if cells are capable of committing towards specific lineages (e.g. osteogenic). These components are important, because if cells are not expanding at a specific rate and are not differentiating towards the lineage desired, the tissue engineered will not mirror the characteristics of native tissue. Therefore, both components are necessary for osteogenic tissue engineering applications. Several stem cell lines have been isolated from different sources (e.g. umbilical, bone marrow) and characterized for their proliferative capacity and their potency. Among these progenitor or stem cell lines, are those isolated from human dental tissue. Due to the similarities between teeth and bone, this specific cell line may be useful in osteogenic tissue engineering applications. In this study, stem cells extracted from human exfoliated deciduous teeth (SHEDs) and periodontal ligament stem cells (PERIOs), were evaluated and compared. Briefly, to evaluate the proliferation rate an ex-vivo expansion study was conducted. This experiment found that both SHEDs and PERIOs were proliferative lines with doubling times of 23 hours and 19 hours respectively. Subsequently, osteogenic differentiation of SHEDs and PERIOs was assessed utilizing a 3-D fibrin gel suspension treated with osteogenic media containing either dexamethasone (DEX) or Retinoic Acid (RA) for 28 days. At day 28, osteogenic markers for collagen 1 (Col1), osteocalcin (OCN), and alkaline phosphatase (ALP) were evaluated using qPCR. Results demonstrated both SHEDs and PERIOs exhibited significant (p<0.05) increases in osteogenic gene expression under the influences of DEX and RA. However the most significant increases were expressed by the SHEDs that received the DEX treatment. Additionally, the synergistic ability of TGF-beta 3 on the osteogenic differentiation of the stem cells was evaluated. Cells were cultured in a 3-D fibrin gel suspension and allowed to differentiate in DEX osteogenic media with and without the supplementation of TGF-beta 3 for 21 days. Using qPCR the cells were evaluated for expression of Col1, OCN, and ALP. In both the SHEDs and PERIOs, the samples treated with TGF-beta 3 the osteogenic gene expression increased in reference to the control, but had a hindering effect compared to cells treated in DEX without the TGF-beta 3. These results from this study suggested, SHED cells grown in 3-D fibrin gel suspension, may be better than PERIO cells for osteogenic tissue engineering applications when treated with DEX media without the supplementation of TGF-beta 3.

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Maluf, Paulo Sérgio Zaidan [UNIFESP]. "Torque na instalação de implantes dentais pós-transplante de fíbula microvascularizado." Universidade Federal de São Paulo (UNIFESP), 2011. http://repositorio.unifesp.br/handle/11600/10118.

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Made available in DSpace on 2015-07-22T20:50:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-27
INTRODUÇÃO: A reabilitação mastigatória com implantes dentais tornou-se, atualmente, uma terapêutica comum e necessária para pacientes edêntulos. Técnicas em implantodontia são aperfeiçoadas constantemente, dentre as quais o torque, para fixação dos cilindros de titânio em osso, considerado fundamental no prognóstico de sucesso da osteointegração. A reconstrução com retalhos microcirúrgicos, em ossos da face, tem sido cada vez mais realizadas em pacientes para reparação de sequelas pós-cirúrgicas. Para a completa reabilitação funcional desses pacientes é necessária a instalação de implantes osseointegráveis para o suporte de próteses dentais, mas inexistem pesquisas que determinem o torque necessário para estabilização inicial, desses implantes, em transplantes ósseos revascularizados. OBJETIVO: Mensurar o torque na instalação de implantes de titânio, em transplante de fíbula microrrevascularizado e consolidado, para reconstrução de maxila e mandíbula. MÉTODOS: Foram instalados 28 implantes dentais, em sete pacientes, com reconstrução cirúrgica em maxila e mandíbula por retalhos microcirúrgicos. No momento da instalação dos implantes mensurou-se o torque para estabilização final, cujos dados foram tabulados e analisados. RESULTADOS: O torque mínimo para instalação dos implantes foi de 20Ncm em 39,3% dos implantes, e o máximo de 45Ncm em 28,5%. CONCLUSÃO: A medida do torque no implante de titânio em transplante de fíbula microrrevascularizado, para reconstrução maxilomandibular, variou de 20 a 45Ncm, não tendo sido observada nenhuma influência relativamente ao gênero, à faixa etária e ao tempo de transplante.
INTRODUCTION: The masticatory rehabilitation with dental implants has become, a therapeutic technique for edentulous patients. Techniques in dental implant are constantly perfected, as the torque to fix the cylinders in a bone, considered fundamental in the prognosis of success in bone integration. The reconstruction with microsurgical flaps, in facial bones, has been increasingly performed in patients to repair the post-surgical sequelae. For the complete functional rehabilitation of these patients, the installation of bone integrable implants is necessary. With the objective of supporting the dental prosthesis, but there are no studies that determine the necessary torque to the initial stabilization of these dental implants in bone revascularized transplants. OBJECTIVE: To measure torque in installation of titanium implants, fibula microrevascularized and consolidated, in reconstruction of maxilla and mandibula. METHODS: Twenty eight dental implants were installed in seven patients with surgical reconstructions in the maxila and mandibular by microsurgical flaps. At the time of the installation of the implants, torque for final stabilization was measured, whose data were tabulated and analyzed. RESULTS: The minimum torque for installation of the implants was of 20Ncm in 39,3% of the implants, and the maximum, of 45Ncm in 28,5%. CONCLUSION: The measure of torque in implants of titanium of fibula microrevascularized transplants, for maxilomandibular reconstruction, varied from 20 to 45Ncm, and no influence related to gender, to age group or to time of transplant has been observed.
TEDE

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Palosaari, H. (Heidi). "Matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs) in mature human odontoblasts and pulp tissue:the regulation of expressions of fibrillar collagens, MMPs and TIMPs by growth factors, transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2)". Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514270789.

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Abstract Dentin formation in physiological and pathological conditions has been widely studied, but the events and regulation are still not completely understood. Odontoblasts, terminally differentiated post-mitotic cells located in a single cell layer around pulp tissue, synthesize and mineralize dentin organic matrix. Growth factors, such as TGF-β1 and BMP-2, have been implicated in the regulation of the responses of odontoblasts and pulp tissue to external irritation. Matrix metalloproteinases (MMPs), a family of 28 endopeptidases collectively capable of degrading virtually all extracellular matrix components, and their specific tissue inhibitors (TIMPs) participate in the organo- and morphogenesis, physiological tissue turnover and pathological tissue destruction in many tissues, but very little is known about their presence, function, and regulation in the dentin-pulp complex cells and tissues. The aim of the work presented in this thesis was to analyze the expression and regulation of collagens, MMPs and TIMPs by TGF-β1 and BMP-2 in mature human odontoblasts and pulp tissue. Odontoblasts synthesize and secrete type I and type III collagens, with no clear effect of TGF-β1 on their expression levels. MMP-1, -2, -8, -9, -10, -11, -14, -15, -16, -19 and TIMP-1, -2, -3 and -4 were expressed by both odontoblasts and pulp tissue. MMP-3 and MMP-12 were not expressed in native odontoblasts or pulp tissue, and MMP-7, -24, and -25 were expressed only in odontoblasts. MMP-2, -10, -14, -20 and -23 were expressed more abundantly in odontoblasts, whereas pulp tissue expressed more MMP-13 and MMP-17. Growth factors differentially regulated the expression of different MMPs and TIMPs within and among the cells and tissues studied. In odontoblasts, MMP-1, -8 and -14 were down-regulated, but MMP-7, MMP-9, TIMP-1 and TIMP-3 up-regulated, by either TGF-β1 or BMP-2, alone or in combination. In pulp tissue, growth factors up-regulated the expression of MMP-1, -2, -10, -13, -17 and TIMP-3, but down-regulated TIMP-4. The widespread of expression of MMPs and TIMPs by mature human odontoblasts and pulp tissue suggests that they may participate in dentin matrix organization prior to mineralization, and that growth factors may further control dentin matrix modeling, not by regulating the synthesis of type I or III collagens as previously believed, but rather by differentially regulating each MMPs and TIMPs.

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Casagrande, Luciano. "Aplicação de princípios de engenharia tecidual no estudo da diferenciação de células-tronco pulpares." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/13251.

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O presente estudo utilizou o modelo fatia-dental/matriz-polimérica para avaliar a influência do tratamento dentinário e das BMPs dentinárias na diferenciação das células-tronco da polpa de dentes decíduos (SHED). Secções transversais (1mm) foram preparadas a partir de terceiros molares humanos extraídos. Matrizes poliméricas a base de ácido poli-L-lático (PLLA) foram criadas no interior da cavidade pulpar das secções dentinárias, tratadas com solução de EDTA a 10%; NaOCl a 5.25%; ou permanecendo sem tratamento. Matrizes poliméricas confeccionadas sem as fatias dentais foram utilizadas como controle. As células (5x104) foram semeadas nas matrizes e, após 7, 14, 21 e 28 dias de cultura in vitro, a expressão de marcadores de diferenciação odontoblástica (DSPP, DMP1 e MEPE) e a proliferação celular (WST-1) foram avaliadas. Células (5x105) semeadas nas matrizes foram transplantadas em camundongos imunodeficientes e cultivadas in vivo por um período de 14 e 28 dias. Para avaliar a atividade das BMPs dentinárias, 5x104 células foram semeadas em matrizes poliméricas com fatia dental e cultivadas na presença de anticorpos anti-BMP- 2, -4, ou -7 (2 μg/ml) durante 14 dias. Adicionalmente, 5x105 células foram tratadas com rhBMP-2, -4, ou -7 (100ng/mL) por 24hs. As células cultivadas in vitro e in vivo alteraram sua expressão genética durante o curso do tempo. DSPP, DMP-1 e MEPE foram expressos por células cultivadas in vitro após 14 dias (tratamento com EDTA e dentina sem tratamento) e in vivo após 28 dias (EDTA), não sendo detectados nos grupos NaOCl e nas células cultivadas nas matrizes sem fatia dental. A proliferação foi reduzida com a diferenciação celular (p<0.05). A utilização de BMP-2/4Ab no meio de cultura exerceu um efeito inibitório na expressão dos marcadores de diferenciação celular, não ocorrendo quando do cultivo das SHED na presença de BMP-7Ab. DSPP, DMP-1 e MEPE foram expressos por células tratadas com rhBMP-2, e DSPP e DMP-1 por células tratadas com rhBMP-4 e -7. Células sem tratamento não expressaram os marcadores. O modelo fatia-dental/matriz-polimérica demonstrou ser adequado para o estudo da diferenciação de células-tronco pulpares, sugerindo que a dentina possa fornecer um microambiente favorável para a diferenciação de celular. As proteínas ósseas morfogenéticas dentinárias BMP-2 e BMP-4 parecem exercer um papel relevante nesse processo.
The effect of dentin pre-treatments and dentin-derived BMPs on SHED differentiation was tested using the Tooth-Slice Scaffold model (TSS). Dentin slices (1mm thickness) were prepared from extracted human third molars. Biodegradable PLLA scaffolds were prepared inside the pulp chamber of the tooth-slices, treated alternatively with a 5.25% NaOCl or 10% EDTA solution, or remaining untreated (WO-T). PLLA sponge scaffolds with no tooth-slice (PSS) were used as control. SHED (5x104) were seeded in TSS and PSS and after 7, 14, 21 and 28 days in culture, RT-PCR (DSPP, DMP1 and MEPE) and WST-1 proliferation assay were performed. Additionally, cells (5x105) were seeded in TSS and PSS and transplanted into SCID mice (14 and 28 days). To verify the dentinderived BMPs bioactivity, SHED (5x104) were cultured in TSS in the presence of antihuman BMP-2, -4, and -7 antibodies for 14 days. Besides, cells in culture were treated with rhBMP-2; -4; or -7 for 24 hours. After in vitro and in vivo time course, SHED altered their genetic expression. The cells cultured in vitro in the TSS (EDTA or WO-T) expressed the differentiation markers after 14 days and maintained expression thereafter. Cell proliferation rate was reduced following the differentiation (p<0.05). Cells transplanted in vivo expressed DSPP, DMP-1 and MEPE after 28 days (EDTA). No transcripts were found in tooth-slices treated with NaOCl or in PSS groups. BMP-2/4Ab prevented the differentiation process and no inhibitory effect was detected for BMP-7Ab. After 24 hours, expression of DSPP, DMP-1 and MEPE was found for rhBMP-2, and DSPP and DMP-1 for rhBMP-4 and rhBMP-7 treated SHED, but not for untreated cells. The tooth slice scaffold model suggests that dentin can provide the environment for SHED differentiation and dentin-derived morphogenic signals BMP-2 and BMP-4 play an important role in this process.

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Le, Luyer Mona. "Évolution dentaire dans les populations humaines de la fin du Pléistocène et du début de l’Holocène (19000 – 5500 cal. BP) : une approche intégrée des structures externe et interne des couronnes pour le Bassin aquitain et ses marges." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0003/document.

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À partir de la fin du Pléistocène, une réduction de la taille des dents humaines et une simplification morphologique ont été observées et débattues en lien avec des changements culturels et environnementaux. Suite à de nouvelles découvertes et à la révision des contextes archéologiques de certains gisements, une réévaluation de la nature des variations de plus de 1900 couronnes dentaires est proposée pour 176 individus de la fin du Paléolithique, du Mésolithique et du début du Néolithique provenant du Bassin aquitain et de ses marges. Particulièrement, les variations de la structure interne (épaisseur de l’émail, proportions des tissus dentaires, morphologie de la jonction émail-dentine) ont été évaluées de manière non invasive grâce aux méthodes d’imagerie 3D (microtomographie) et de morphométrie géométrique afin de caractériser et d’interpréter l’évolution des couronnes dentaires selon une approche intégrée. Les résultats des analyses morphométriques montrent une discontinuité entre les populations de la fin du Pléistocène et celles du début de l’Holocène. Une réduction des dimensions externes, des épaisseurs de l’émail et des proportions des tissus est mesurée entre la fin du Paléolithique et le Mésolithique, alors que des différences majeures dans les types d’usure et la distribution de l’émail sont observées entre le Mésolithique et le Néolithique. Ces données suggèrent que les modifications induites par les changements environnementaux de l’Holocène ont eu un impact plus important sur la réduction dentaire dans les populations humaines et que les changements culturels néolithiques ont surtout affecté la distribution de l’émail. Enfin, une corrélation entre le type d’usure occlusale et la distribution de l’épaisseur de l’émail a été mise en évidence et associée à des changements de régime alimentaire. En particulier, l’épaisseur de l’émail peut évoluer rapidement comme une réponse sélective aux changements fonctionnels dans la biomécanique de la mastication
Since the Late Pleistocene, a reduction in size and a morphological simplification of human teeth have been observed and arguably linked to cultural and environmental changes. Following new discoveries along with the revision of key archaeological contexts, a re-assessment of the nature of crown variations on more than 1900 teeth is proposed for 176 Late Paleolithic, Mesolithic and Early Neolithic individuals from the Aquitaine Basin and its margins. In particular, a non-invasive assessment of internal tooth structure variability (enamel thickness, dental tissue proportions, enamel-dentine junction morphology) has been performed using 3D imaging methods (microtomography) and geometric morphometrics in order to characterize and interpret dental evolution from a whole crown perspective. Results from the morphometric analyses show a discontinuity between Late Pleistocene and Early Holocene populations. External dimensions, enamel thicknesses and tissue proportions are reduced in Mesolithic individuals compared to those of the Late Paleolithic, while major differences are observed in occlusal wear patterns and enamel distribution between Mesolithic and Early Neolithic samples. These data suggest that environmentally-driven modifications during the Early Holocene had a major impact on dental reduction in human populations and that Neolithic cultural changes had mostly affected enamel distribution. Finally, a correlation between occlusal wear pattern and enamel thickness distribution is observed and associated with dietary changes. In particular, enamel thickness may have rapidly evolved as a selective response to functional changes in masticatory biomechanics

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Pedroni, Ana Clara Fagundes. "Efeito da Laserfototerapia associada ou não à Vitamina C na indução de membranas celulares (cell sheets) de células-tronco da polpa dentária humana." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-03082016-112215/.

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Membranas celulares (MCs; Cell Sheets), constituídas por células-tronco (CTs), são autodestacáveis da placa de cultivo, e sem subcultivos geram grande quantidade de células que podem ser transplantadas de maneira mais próxima da fisiologia celular, mantendo-se as ligações celulares e a matriz extracelular produzidas em cultura. O ácido ascórbico ou vitamina C (VC) tem efeito indutor da formação destas MCs, aumentando a longevidade e tempo de indiferenciação das CTs. A similaridade observada entre respostas biológicas da VC em MCs e aquelas da Laserfototerapia (LFT) sobre células e tecidos, nos levou à hipótese de que estas terapias poderiam se complementar melhorando o prognóstico de futura aplicação clínica dessas MCs em regenerações de tecidos de interesse odontológico. Para testar essa hipótese, LFT e VC foram aplicadas associadas ou não na indução de MCs de células-tronco da polpa dentária humana (hDPSCs). Para tanto, hDPSCs descongeladas, que expressaram níveis típicos de marcadores de superfície de células-tronco mesenquimais, foram plaqueadas em placas de 6 poços (5x104 células por poço). Vinte e quatro horas depois do plaqueamento as culturas foram submetidas aos tratamentos dos grupos experimentais: Controle: hDPSCs em P3 cultivadas com meio clonogênico; Senescente: hDPSCs em P27 cultivadas com meio clonogênico; VC: P3 cultivadas com meio clonogênico acrescido de VC (20 ?g/ml); Laser: P3 cultivadas com meio clonogênico e submetido à LFT (contato e pontual - 5 pontos / poço, 660 nm, 20 mW, 0,028 cm², 0,71 W/cm², 7 segundos, 5 J/cm², 0,14 J por ponto, 48 horas de intervalo) e Laser+VC: P3 cultivadas com meio clonogênico acrescido de VC e submetido à LFT. Em 24 horas, 7 e 13 dias as hDPSCs dos diferentes grupos experimentais foram observadas macro e microscopicamente, e atividade da enzima telomerase foi avaliada por PCR-TRAP, complementado por ELISA. Para a avaliação da expressão de genes relacionados à natureza e indiferenciação (Mitofilina e Oct 4) e à longevidade (fase catalítica da enzima telomerase - hTERT); bem como à senescência das células do grupo senescente (?-galactosidase), as hDPSCs de todos os grupos experimentais foram submetidas ao RT-qPCR As hDPSCs foram capazes de formar MCs somente nos grupos VC e Laser+VC (100%), entre 10 e 13 dias. As MCs do grupo Laser+VC apresentaram maior facilidade na manipulação. Atividade de Telomerase nas hDPSCs foi observada somente em 24 horas (Controle e LFT) e em 7 dias (VC e Laser+VC). Os marcadores de indiferenciação (Oct 4) e mesenquimal (mitofilina), bem como a hTERT foram expressos nas hDPSCs de todos os grupos experimentais. O Oct4 e o hTERT, em 7 dias, apresentaram expressões significativamente maiores nos grupos VC e Laser+VC em comparação com os demais (p < 0,0001, p = 0,0009, respectivamente). A expressão da mitofilina foi significativamente maior no grupo Laser+VC, em 7 dias (p =0,033). A técnica de obtenção de MCs de hDPSCs por essa metodologia foi considerada adequada para ser testada em procedimentos regenerativos. A LFT quando associada à VC não interferiu na formação das MCs, nem na manutenção da longevidade e indiferenciação das hDPSCs. Adicionalmente, a LFT melhorou a manipulação das MCs. Assim sendo, a associação de VC e LFT na indução de MCs parece promissora para futura utilização de MCs na odontologia regenerativa.
Cell Sheets, consisting of stem cells (SCs) are self detachable from the cultivation plate, and with no subcultivation can generate large amount of cells. The cell sheets can be transplanted closer to cell physiology environment by keeping the cell connections and the extracellular matrix produced in culture. Ascorbic acid or Vitamin C (VC) has inductive effect on cell sheet formation, increasing the longevity and the stemness of the cell for long period of time. The similarity between biological responses of VC in cell sheets and those of Laserphototherapy (LPT, Laser) on cells and tissues led us to hypothesize that these therapies could improve the prognosis of future clinical application of these cell sheets in regeneration of dental tissues. To test this hypothesis, LPT and VC were applied, associated or not, to induce human dental pulp stem cells (hDPSCs). Therefore, hDPSCs, which expressed typical levels of mesenchymal stem cell surface markers, were plated in 6-well plates (5x104 cells per well). Twenty-four hours later they were subjected to the treatment of experimental groups: Control: hDPSCs in P3 cultured with regular medium; Senescent: hDPSCs in P27 cultured with regular medium; VC: P3 cultured with regular medium supplemented with VC (20 ?g/ml); Laser: P3 cultures with regular medium and submitted to LPT (punctual and contact mode-5 points / well, 660 nm, 20 mW, 0.028 cm², 0.71 W/cm², 7 sec, 5 J/cm², 0.14 J per point, 48 hours-intervals) and Laser+VC: P3 cultured with regular medium supplemented with VC and submitted to LPT Within 24 hours, 7 and 13 days the hDPSCs of the different experimental groups were observed macroscopically and microscopically, and the telomerase enzyme activity was assessed by PCR-TRAP, complemented by ELISA. To evaluate the expression of genes related to the nature and differentiation (Mitofilina and Oct 4), longevity (catalytic phase of telomerase-hTERT enzyme), and the senescence of the senescent group cells (?-galactosidase), the hDPSCs of all experimental groups were subjected to RT-qPCR. The RT-qPCR data were compared by ANOVA complemented by the Tukey\'s test (p <= 0.05). The hDPSCs were able to form cell sheets only in the VC and Laser+VC groups (100%). Additionally, the cell sheets of the Laser+VC group presented easier handling. Telomerase activity in hDPSCs was observed only in 24 hours (Control and Laser) and seven days (VC and Laser + VC). The undifferentiating marker (Oct 4) and mesenchymal marker (mitofilin), as well as hTERT were expressed in hDPSCs of all experimental groups. Oct4 and hTERT presented expressions significantly higher at 7 days in VC and Laser+VC groups than in all other groups (p < 0.0001, p = 0.0009, respectively). The expression of mitofilin was significantly higher in the Laser+VC group, in 7 days (p = 0.0338). The technique of obtaining cell sheets of hDPSCs by the methodology here presented was considered appropriate to be further tested in regenerative procedures. The LPT when combined with VC did not interfere with the formation of the cell sheets, neither in the maintenance of longevity and undifferentiating status of hDPSCs. Moreover, LPT improved the handling of the cell sheets. Thus, the association of VC and LPT in the induction of cell sheets seems promising for future use in regenerative dentistry.

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Neto, Eduardo Felippe Duailibi. "Desenvolvimento de metodologia radiográfica e volumétrica dos diferentes estágios de desenvolvimento dentário para qualificação de material biológico em Engenharia Tecidual." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/23/23139/tde-28052013-194243/.

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A utilização de Células-tronco e técnicas da Engenharia Tecidual representa um grande avanço tecnológico e beneficiará muitos pacientes com suas conquistas. A descoberta de germes dentários como uma fonte confiável de células-tronco possibilitou diversas pesquisas nesta área. Duailibi et al. (2011) sugeriram uma nova classificação de desenvolvimento dentário baseada pela quantidade de material biológico coletado indicando a necessidade de métodos de diagnóstico por imagem para esta nova classificação. Na literatura diversos trabalhos indicam métodos de classificação dentária e métodos para estimar a idade fisiológica de indivíduos. O presente estudo tem o objetivo de adaptar alguns destes métodos para estimar o estágio de desenvolvimento proposto por Duailibi et al. (2011) consequentemente indicando a quantidade de células-tronco esperadas nas amostras. Para tanto, submeteu-se uma coleção de 67 dentes previamente classificados por Duailibi et al. (2011) à técnica rpcl e à tcfc para a obtenção de imagens e a aplicação de técnicas de estimativas por proporções lineares e volumétricas. Os resultados por análises lineares indicaram valores de R2 para o método de proporção de comprimento CDCP de 0,14050; CCCP de 0,65369; CCCR de 0,5408; CDCR de 0,54074; o método de proporção de área APAD de 0,23925; e método de proporção de volume VPVD de 0,08553, com valor de p menor ou igual à 0,05. Concluindo este estudo indica-se o método de rpcl utilizando a análise do comprimento entre coroa e polpa como o mais indicado para estimar o estágio de desenvolvimento.
The usage of human dental stem cells and tissue engineering technics represents a huge tecnological development and it may benefits many patients in a promissing future. The discovery of suitable source of human dental stem cells were made using tooth buds. Duailibi et al. 2011 indicated a new tooth classification on a stem cell harvesting based research, sugesting new methods for diagnosis these stages. Several method were developed for dental age assesement. The presente study aims to evaluate some of these dental age technics and make adaptations for estimating Duailibi et al. 2011 tooth stages. A 67 tooth sample previoulsy classificated by Duailbi et al. 2011 were submited through periapical parallel long cone X-rays and CBCT analysis. Age estimation ratio methods were applied by measuring tooth/root lenth, crown/root lenth, tooth/pulp lenth, crown/pulp lenth, tooth/poulp área and tooth/pulp volume. Results indicated by linear regression analisys a R2 value of tooth/pulp lenth 0,14050; crown/pulp lenth 0,65369; crown/root lenth 0,5408; tooth/root lenth 0,54074; pulp/tooth volume 0,23925; e tooth/pulp volume de 0,08553, with p value of 0,005. In conclusion , the best method for estimating Duailibi et al. 2011 tooth classification techinic is made by using periapical long cone X-rays using crown/pulp lenth ratio.

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Nicola, Fabrício do Couto. "Efeito neuroprotetor do transplante de células-tronco mesenquimais derivadas de dente decíduo humano em ratos Wistar submetidos à lesão medular." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/170284.

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A lesão medular (LM) é uma patologia incapacitante que resulta em déficits sensoriais e motores. No Brasil, a incidência anual é de 30 novos casos de lesão medular a cada 1 milhão de indivíduos e, infelizmente, a LM permanece sem um tratamento eficaz. Células-tronco derivadas do dente decíduo humano estão entre as potenciais fontes de células-tronco para transplante após a lesão medular, cujo objetivo é de promover a proteção ou a recuperação da lesão na medula espinal. Buscou-se nesta tese avaliar os efeitos do transplante, uma hora após a lesão, das células tronco de dente decíduo humano (SHED) no período agudo, subagudo e crônico sobre a neuroproteção, proteção tecidual e recuperação funcional em ratos Wistar submetidos à lesão medular por contusão. Os principais objetivos foram: a) investigar os efeitos do transplante das SHED sobre a recuperação funcional, volume da lesão e morte neuronal; b) verificar os efeitos do transplante sobre as células progenitoras, formação da cicatriz glial e modificações astrocitárias após o modelo de contusão medular Observou-se a melhora na recuperação funcional, redução do volume da lesão e morte neuronal na medula espinal dos animais que receberam o transplante de SHED após a lesão medular. As SHED aumentam o número de células precursoras na medula espinal, no período subagudo, reduzem a expressão da proteína fibrilar glial ácida (GFAP) e aumentam a expressão do canal retificador de influxo de potássio 4.1, ambas proteínas astrocitárias. Concluímos que o transplante de células-tronco derivadas do dente decíduo humano após a lesão medular promove a recuperação funcional a partir do efeito neuroprotetor iniciado na fase aguda, confirmado pelo maior número de neurônios motores presentes seis semanas após a contusão. As SHED são capazes de aumentar o número de células precursoras e de produzir modificações astrocitárias na medula espinal de ratos lesados na fase subaguda, reduzindo a formação da cicatriz glial.
Spinal cord injury (SCI) is a disabling condition that results in sensory and motor deficits. The estimated annual incidence in Brazil is of 30 new cases of spinal cord injury per 1 million of individuals; unfortunately SCI remains without an effective treatment. Stem cells from human exfoliated deciduous teeth (SHED) are one among potential sources of stem cells for transplantation after spinal cord injury in order to promote protection or tissue and functional recovery after spinal cord injury. The aim of this Thesis was to evaluate the effects of stem cells from human exfoliated deciduous teeth (SHED) transplantation, one hour after lesion, in the acute, subacute and chronic phases on neuroprotection, tissue protection and functional recovery in Wistar rats submitted to spinal cord injury by contusion The main goals were: a) to investigate the effects of SHED transplantation on functional recovery, lesion volume, and neuronal death; b) to verify the effects of the transplantation on the progenitor cells number, glial scar formation and astrocytic modifications after spinal cord contusion. Improvement of functional recovery, reduction of lesion volume and neuronal death were observed in the spinal cord of animals submitted to spinal cord injury and SHED transplantation. SHEDs increased the number of precursor cells in the spinal cord in the subacute period, reduced the expression of glial fibrillary acidic protein (GFAP) and increased the expression of the potassium influx rectifier channel 4.1, both astrocyte proteins. We conclude that transplantation of stem cells from human exfoliated deciduous teeth after spinal cord injury promotes functional recovery from the neuroprotection effect, which starts in the acute phase and is confirmed six weeks after the contusion with a higher number of motor neurons in the ventral horn of spinal cord. SHEDs are able to increase the number of precursor cells and produce astrocyte modifications in the spinal cord of injured rats in the subacute phase, reducing glial scar formation.

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20

Domínguez, Santamaría Juan Mario. "Importancia de la relación de ayuda en la entrevista familiar de donación de órganos de fallecidos: una perspectiva de los profesionales sanitarios." Doctoral thesis, Universidad de Alicante, 2011. http://hdl.handle.net/10045/23521.

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21

Oxilia, Gregorio. "Human dental tissues: Advancement in virtual dental analysis." Doctoral thesis, 2018. http://hdl.handle.net/2158/1119840.

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The subject of this doctoral dissertation concerns the usefulness of virtual analysis approach in studies of dental tissues and their defects. The real symmetry and perfect balance between opposite jaw halves and antagonistic teeth is not the reality in the masticatory system. The sample of Yuendumu Aboriginal people used in Paper I consists of complete maxillary and mandibular dental arch 3D models from 19 individuals (young and adult). The analysis was carried out on first molars from all quadrants and only individuals with similar levels of wear were selected (76 teeth in total). Virtual methods were applied in order to inspect the palatal arch asymmetries in relation to the alveolar bones inclination and consequently, the alteration of dental crown. Crown alteration (Enamel and Dentine) could be produced by several factors such as masticatory activity, pathological, anthropic and cultural alterations. However, anthropological studies are sometimes not able to distinguish differences among them without an interdisciplinary approach. Particularly, pathological alterations (pits and fissures) are extremely difficult to interpret without microscopy analysis. That is the reason why a virtual approach in dental studies is useful to understand and distinguish any natural or anthropic alteration. Two examples are shown in Paper II and Paper III where two dental treatments discovered in two Italian sites have been described: Villabruna specimen and Fredian shelters. The modern human specimen Villabruna (Paper II) from a burial in Northern Italy is the earliest evidence of dental therapeutic intervention on a Late Upper Paleolithic (ca. 14,000 yr BP). Using Scanning Electron Microscopy (SEM) we showed the presence of striations deriving from the manipulation of a large occlusal carious cavity of the lower right third molar. The striations have a “V’’-shaped transverse section and several parallel micro-scratches at their base, as typically displayed by cutmarks on teeth. Based on in vitro experimental replication and a complete functional reconstruction of the Villabruna dental arches, we confirmed that the identified striations and the associated extensive enamel chipping on the mesial wall of the cavity were produced ante-mortem by pointed flint tools during scratching and chiseling activities. Similar situation was identified at the Fredian shelter (Paper III). The two upper incisors display exposed pulp chambers with circumferential enlargement, chipped dentine on the cavity margins and striations on the cavity walls. Histochemical analysis of the material embedded at the bottom of the cavities revealed a conglomerate of vegetal fibers and probably hairs. Moreover, Fourier transform infrared spectroscopy (FTIR), energy dispersion X-ray spectroscopy (EDS), and Raman microscopy analysis of black residue adhering to the walls of both cavities is consistent with organic substances, specifically bitumen. A direct chronometric date for Fredian 5 confirms a Late Upper Paleolithic context (between 13,000-12,735 calendar years ago). Overall, our results are consistent with in vivo dental drilling to remove necrotic or infected pulp tissue (pulpitis) and the subsequent use of a composite, organic dental filling in the cavity. The conservation of human remains is the main interest of good anthropological research and any organic matter identified within a dental cavity needs to be conserved. This is the topic of paper IV: Letter to the Editor I had written in order to clarify the reason why we have decided to use three different methods (infrared spectroscopy (FTIR), energy dispersion X-ray spectroscopy (EDS), and Raman microscopy analysis) rather than gas-chromatography. Finally, when a tooth does not show any pathological alteration or exhibits a normal/slight wear pattern on the occlusal surface (wear stage 1-2, 3 Smith, 1974) it is possible to obtain information regarding taxonomy based on volume (3D) or areas (2D) of Enamel, Dentine (paper V, VI, VII. VIII) and morphometric analysis of teeth's root (paper IX). This thesis therefore strives to provide a contribution to understanding how virtual approach to dental studies can be used to increase the knowledge of dental tissues and their defects.

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22

Beaumont, Julia, Andrew R. Gledhill, Julia A. Lee-Thorp, and Janet Montgomery. "Childhood diet: a closer examination of the evidence from dental tissues using stable isotope analysis of incremental human dentine." 2013. http://hdl.handle.net/10454/5636.

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No
Incremental dentine analysis utilizes tissue that does not remodel and that permits comparison, at the same age, of those who survived infancy with those who did not at high temporal resolution. Here, we present a pilot study of teeth from a 19th-century cemetery in London, comparing the merits of two methods of obtaining dentine increments for subsequent isotope determination. Covariation in ¿13C and ¿15N values suggests that even small variations have a physiological basis. We show that high-resolution intra-dentine isotope profiles can pinpoint short-duration events such as dietary change or nutritional deprivation in the juvenile years of life.

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23

Cardona, Dayana Elisa Jacinto Baptista de. "Análise macroscópica e radiográfica de tecidos e materiais dentários sujeitos a altas temperaturas." Master's thesis, 2018. http://hdl.handle.net/10400.14/26080.

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Introdução: existem situações forenses envolvendo exposição a altas temperaturas, nomeadamente por ação de chamas, em que ocorre uma significativa destruição corporal do cadáver. A caracterização dos tecidos mineralizados e dos materiais dentários torna-se particularmente relevantes nestes casos, na medida em que poderá permitir ate o estabelecimento de uma correlação com a temperatura de exposição a que esteve sujeito o cadáver. Em situações extremas de temperatura elevadas, a identificação dentaria, per si, pode tornar-se impossível, principalmente quando ocorre uma completa destruição dos dentes ou quando os registos clínicos ante mortem são inexistentes. Devendo preferencialmente proceder-se a análise dos dentes, tendo em conta a sua excelência em termos de preservação. Objetivos: Observar as mudanças macroestruturais e radiográficas dos tecidos dentários e dos materiais de restauração dentária utilizados na atualidade, ao serem submetidos a diferentes temperaturas. Verificar a capacidade de as alterações observadas serem utilizadas a nível da identificação forense, nomeadamente em casos de cadáveres queimados, carbonizados ou incinerados. Materiais e métodos: Realizou-se um estudo experimental in vitro para observar as mudanças físicas macroscópicos e radiográficos dos tecidos dentários e alguns materiais dentários. O protocolo proposto envolve 36 dentes humanos divididos em 3 grupos, de 12 dentes restaurados com de amálgama, resina composta e ionómero de vidro, estos dentes foram submetidos a 3 faixas de temperatura (600°C, 900°C e 1100°C) o que corresponde a dentes para cada temperatura proposta. Resultados: Os tecidos e os materiais dentários estudados nesta investigação apresentam grande resistência em altas temperaturas sem variar consideravelmente sua macroestructura, de tal maneira que as mudanças físicas (estabilidade dimensional, fissuras, gretas, fraturas, textura, cor, carbonização e incineração) podem chegar-se a identificar e associar-se à cada faixa de temperatura específica. Conclusão: Os tecidos e os materiais dentários apresentam grande resistência em ação de altas temperaturas. Do mesmo modo, apresentam mudanças específicas (cor, textura, fissuras, gretas, fraturas e fragmentação) que podem contribuir com o processo de identificação de um cadáver ou restos humanos queimados, incinerados ou carbonizados.
In forensic situations involving exposure to high temperatures, in particular by the action of fire, a significant destruction of the cadaver occurs. The characterization of the mineralized tissues and dental restoration materials becomes particularly important in these cases, as it correlates with the temperature to which the corpse was exposed. In extreme situations of high temperature dental identification may be impossible, especially when a complete destruction of the tooth occurs or when ante mortem clinical records are nonexistent. Preferentially, we should proceed with the analysis of the teeth, taking into account their excellence in terms of preservation. Objectives: To observe the macro-structural and radiographic changes of the dental tissues and dental restoration materials used at present, when subjected to different temperatures. Checked the capacity of the observed alterations being used at the level of forensic identification, jointly in cases of cadavers burned, cribbed or incinerated. Materials and methods: An in vitro experimental study was carried out to observe the macroscopic and radiographic physical changes of the dental tissues and some dental materials. The protocol involved wrapped 36 human teeth divided into 3 groups, of 12 teeth restored with amalgam, composite resin and glass ionomer, these teeth were subjected to 3 temperature ranges (600 ° C, 900 ° C and 1100 ° C) which correspond to teeth for each propustate temperature. Results: The tissues and dentinal materials studied in this research present great resistance at high temperatures without significantly varying their macrostructure, so that physical changes (dimensional stability, cracks, cracks, fractures, texture, color, carbonization and incineration) can get to identify and associate with each specific temperature range. Conclusion: The tissues and dental materials present great resistance in action of high temperatures. In the same way, they present specific changes (color, texture, fissures, cracks, fractures and fragmentation) that can contribute to the process of identifying a corpse or human remains burned, incinerated or charred.

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24

Baker, Ryan William. "Effects of DynaMatrix® Membrane on Angiogenic Cytokine Expression From Human Dental Pulp Stem Cells." Thesis, 2013. http://hdl.handle.net/1805/3718.

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Indiana University-Purdue University Indianapolis (IUPUI)
The aim of this current study was to determine if the exposure of human dental pulp stem cells (HDPSC) to the DynaMatrix membrane will result in an increased production of angiogenic cytokines that are critical for pulp/root regeneration. Angiogenesis cytokine arrays have been established as a viable method for assessing expression of cytokines.20 HDPSC were chosen as they are expected to be found in the apical papilla and the infected immature root canal system of teeth that current regenerative endodontic techniques are designed to treat.

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25

Al-Mosawi, M., G. R. Davis, A. Bushby, J. Montgomery, Julia Beaumont, and M. Al-Jawad. "Crystallographic texture and mineral concentration quantification of developing and mature human incisal enamel." 2018. http://hdl.handle.net/10454/16576.

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Yes
For dental human enamel, what is the precise mineralization progression spatially and the precise timings of mineralization? This is an important question in the fundamental understanding of matrix-mediated biomineralization events, but in particular because we can use our understanding of this natural tissue growth in humans to develop biomimetic approaches to repair and replace lost enamel tissue. It is important to understand human tissues in particular since different species have quite distinct spatial and temporal progression of mineralization. In this study, five human central incisors at different stages of enamel maturation/mineralization were spatially mapped using synchrotron X-ray diffraction and X-ray microtomography techniques. From the earliest developmental stage, two crystallite-orientation populations coexist with angular separations between the crystallite populations averaging approximately 40o and varying as a function of position with the tooth crown. In general, population one had significantly lower texture magnitude and contributed a higher percentage to the overall crystalline structure, compared to population two which only contributed 20-30% but had significantly higher texture magnitude. This quantitative analysis allows us to understand the complex and co-operative structure-function relationship between two populations of crystallites within human enamel. There was an increase in the mineral concentration from the enamel-dentin junction peripherally and from the incisal tip cervically as a function of maturation time. Quantitative backscattered-electron analyses revealed that mineralization of prism cores precedes that of prism boundaries. These results provide new insights into the precise understanding of the natural growth of human enamel.
Partly funded by NERC grant ”Timelines in Teeth” NE/F018096/2.

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26

Masumbuko, Kahamba Nyota. "Isolation, culture and neurogenic differentiation of human dental stem cells." Thesis, 2016. http://hdl.handle.net/10539/21593.

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A Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree Of Master of Science in Medicine, 2016.
Dental stem cells (DSCs) have been identified in teeth and their supporting tissues. They represent an exclusive source of adult stem cells, easily isolated and manipulated for tissue repair and regeneration. This research project evaluated the neurogenic potential of the dental pulp stem cells (DPSCs) and stem cells from the pulp of human exfoliated deciduous teeth (SHEDs) in a South African cohort. Sixty non-carious permanent and deciduous teeth were extracted from healthy patients aged between 18 and 30 years and 5 and 10 years, at the University of the Witwatersrand's Oral Health Clinic in Johannesburg Charlotte Maxeke Academic Hospital, South Africa. The cells, isolated from the extracted pulp tissue were cultured, counted and then phenotyped by flow cytometry analysis. The cells were further expanded in a neural induction medium and immunocytochemistry analysis for Ki-67, doublecortin (DCX) and nestin were performed. Large colonies of both DPSCs and SHEDS were harvested from the extracted pulp tissues and positively cultured. Flow cytometry analysis confirmed the presence of CD44+ and CD29+ cells as well as the known mesenchymal stem cell markers CD90 and CD105. Both DPSCs and SHEDs demonstrated successful proliferation and neural differentiation. This study confirmed that DPSCs and SHEDs are highly proliferative human adult stem cells that exhibit a neurogenic potential that may contribute in the treatment of neurological disorders.
AC2017

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27

Adams, Joseph Benjamin. "Effects of DynaMatrix® on angiogenic cytokine expression from human dental pulp fibroblasts : an in vitro study." Thesis, 2015. http://hdl.handle.net/1805/6494.

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Indiana University-Purdue University Indianapolis (IUPUI)
EFFECTS OF DYNAMATRIX® ON ANGIOGENIC CYTOKINE EXPRESSION FROM HUMAN DENTAL PULP FIBROBLASTS: AN IN VITRO STUDY by Joseph Benjamin Adams Indiana University School of Dentistry Indianapolis, IN Introduction: An exogenous scaffold may lead to more predictable pulp tissue regeneration and continued root formation in a regenerative endodontic procedure. DynaMatrix® is a natural membrane scaffold made of porcine small intestine, currently used in periodontal regenerative surgeries. Objective: The purpose of this study was to investigate if human dental pulp fibroblasts (HDPFs) seeded on DynaMatrix® membrane would result in an increase in the expression of angiogenic cytokines. Materials and Methods: HDPFs (75,000 per well) were seeded in 6-well plates. Three groups were tested: Group 1 (C): HDPFs in 70 media only; Group 2 (M): DynaMatrix® (Cook Biotech, Indianapolis, IN) alone in media; and Group 3 (C+M): HDPFs seeded on DynaMatrix® membranes. After 72 hours of incubation in serum positive, the conditioned media were collected and analyzed for the expression of 20 angiogenic cytokines utilizing RayBiotech Inc., arrays per the manufacturer’s instruction. The data were analyzed by ANOVA. Results: Group M was significantly higher than C for bFGF (p = 0.0023). C+M was significantly higher than M for ANG (p = 0.0104); GRO (p = 0.0003); IFN-γ (p = 0.0023); IL-6 (p = 0.0003); IL-8 (p = 0.0003); Leptin (p = 0.0003); MCP-1 (p = 0.0104); TIMP-1 (p = 0.0190); TIMP-2 (0.0123). C was significantly higher than C+M for ANG (p = 0.0104); MCP-1 (p = 0.0104); and THPO (p = 0.0308). Cytokines such as b-FGF, ANG, and leptin promote angiogenesis, and stimulate migration and proliferation of cells. Conclusion: The cytokine expression profile from the cells seeded on DynaMatrix® suggests that it might be a suitable scaffold for regenerative endodontic procedures. It could improve vascularization by increasing angiogenic cytokines in the microenvironment of the treated root canal and supporting tissue regeneration.

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28

Macho, Gabriele A., D. Shimizu, and I. R. Spears. "The effect of prism orientation and loading direction on contact stresses in prismatic enamel: implications for interpreting wear patterns." 2005. http://hdl.handle.net/10454/3551.

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No
The ability of prisms to effectively dissipate contact stress at the surface will influence wear rates in teeth. The aim of this investigation was to begin to quantify the effect of prism orientation on surface stresses. Seven finite element models of enamel microstructure were created, each model differing in the angulation of prism orientation with regard to the wear surface. For validation purposes, the mechanical behavior of the model was compared with published experimental data. In order to test the enamel under lateral loads, a compressed food particle was dragged across the surface from the dentino-enamel junction (DEJ) towards the outer enamel surface (OES). Under these conditions, tensile stresses in the enamel model increased with increases in the coefficient of friction. More importantly, stresses were found to be lowest in models in which the prisms approach the surface at lower angles (i.e., more obliquely cut prisms), and highest when the prisms approached the surface at 60° (i.e., less obliquely cut). Finally, the direction of travel of the simulated food particle was reversed, allowing comparison of the difference in behavior between trailing and leading edge enamels (i.e., when the food particle was dragged either towards or away from the DEJ). Stresses at the trailing edge were usually lower than stresses at the leading edge. Taken together with what is known about prism orientation in primate teeth, such findings imply greater wear resistance at the intercuspal region and less wear resistance at the lateral enamel at midcrown. Such findings appear to be supported by archeological evidence.

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29

Nirmalasari, Putu Risti, and 李思媞. "The Effects of Natural Teeth with Different Interface Tissue around Implant towards Significant Direction of Resonance Frequency Vibration of Dental Implant on Human Mandible by Resonance Frequency Analysis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/qfg5k7.

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碩士
國立中央大學
機械工程學系
105
Abstract The work within this thesis investigates the significant direction of resonance frequency for osseointegration assessment. The significant directions of resonance frequencies give information to support the resonance frequency analysis. This study discusses about the influence of natural teeth and interface tissue as the structures around dental implantation to the resonance frequencies. The analysis performed in numerical by using modal analysis and harmonic response analysis from ANSYS Workbench Software Inc. Modal analysis determine the natural frequencies and mode shapes of a structure, whereas harmonic response analysis determine the resonance frequencies spectrum. After the highest resonance frequency obtained on the spectrum, it plotted into the radar graph and see the direction trend line in certain mandible models. The analysis based on the theories of dynamic structure by using finite element method. The analysis of cantilever beam and artificial bone block were performed as an initial analysis to explain phenomena that occur in the main case (mandible models). Cantilever beam used two different types of cross-sections, circular and rectangular. The resonance frequency results of circular cross-section were all the same in different excitation directions, vice versa for rectangular cross-section. Artificial bone block was modeled with cortical thickness without-interface tissue, 2mm. The resonance frequency value in buccal-lingual (BL) direction is higher than mesial-distal (MD) direction. The other artificial bone blocks were modeled in two different conditions of interface tissue with cortical thickness, 1mm. The result showed that the behavior of a physical structure without-interface tissue is stiffer than with-interface tissue but the mode shapes remain the same. In this thesis, the mandible was varied into three different models, based on position of teeth beside implant structure with different interface tissue stiffness. Model-1 was mandible with teeth beside implant structure; Model-2 was mandible without teeth beside implant structure; Model-3 was the mandible with teeth only on one side of implant structure. Interface tissue was varied into three different values of Young’s modulus (2, 25, 137 MPa) and it applied on each mandible models. The result showed the lower stiffness (2MPa) had almost the same resonance frequency in every direction, vice versa for higher stiffness (25, 137MPa) which had a significant direction in different excitation load directions. Keywords: significant direction, resonance frequencies (RFs), mode shape, resonance frequency analysis (RFA), finite element analysis (FEA).

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