Este estudo teve como finalidade analisar experimentalmente a aplicação de diferentes tamanhos de grânulos de hidroxiapatita em falhas ósseas produzidas em ambos os fêmures de ratos machos da raça Wistar e investigar as correlações dos tamanhos dos grânulos com a quantidade de tecido ósseo neoformado. Cada falha óssea foi preenchida com um dos três tamanhos de grânulos de hidroxiapatita utilizados neste estudo (212 &#956, 500&#956 e 1000&#956). Os animais foram divididos em 3 grupos experimentais compostos por 15 animais cada, sendo que cada grupo foi sacrificado de acordo com a data do sacrifício: 30, 90 e 180 dias de período de pós-operatório, respectivamente e posteriormente submetidos ao estudo histológico. No terceiro grupo experimental, foi também realizado estudo radiológico no período de pós-operatório imediato, aos 30, 90 e 180 dias. O grupo controle, composto por 10 animais, que não tiveram preenchimento de suas falhas ósseas , foram submetidos aos estudos histológico e radiológico nos mesmos períodos que o terceiro grupo experimental. De acordo com os resultados dos estudos radiológico e histológico, concluiu-se que a hidroxiapatita empregada foi biocompatível, no entanto, atrasou o processo de reparação óssea na falha, enquanto que o grupo controle apresentou os melhores resultados, com completa reorganização da falha óssea com apenas 90 dias de período de pós-operatório. / This study evaluated the hydroxyapatite granules osteointegration in defects produced on both femurs of Wistar rats. The defects were filled with one of the three different sizes of hydroxyapatite granules (212&#956, 500&#956 and 1000&#956). The rats were divided in 3 groups of 15 animals, which were sacrificed at 30, 90 and 180 days after the operation, followed by histological study of the femurs and radiological study ofthe latter group. The control group, of 10 animals, had no fllling of it\'s defects and had radiological study and were sacrificed at 180 days after the operation, followed by histological study. It concludes from radiological and histological studies that all sizes of hydroxyapatite granules applied were biocompatible, although it delayed the bone repair. In this study the bone restoration was better observed on the control group.

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

Reproduction de : Thèse de doctorat : Mécanique et matériaux : Reims : 2005. / Titre provenant de l'écran titre. Bibliogr. f.

No description available.

An in vitro model system utilizing de-mineralized periodontium tissues was developed for investigating the molecular controls involved in the spatial deposition of minerals on collagenous tissues. Preferential mineral deposition was observed when the de-mineralized tissue sections were incubated in solutions containing a supersaturation of calcium and phosphate ions with respect to hydroxyapatite (HA). Energy dispersive X-Ray (EDX) analysis demonstrated that these minerals are likely to be octacalcium phosphate (OCP) or dicalcium phosphate dihydrate (DCPD); further characterization with a secondary technique is required to draw a more definitive conclusion. The role of collagen fibrils in mineralization was tested by removing all the non-collagenous components from the tissue sections with proteolytic enzymes and exposing them to similar mineralization conditions as the control samples. A substantially less amount of minerals were formed in these samples; this correlates well with the hypothesis in the literature that collagen fibrils alone cannot initiate mineral formation.

An in vitro model system utilizing de-mineralized periodontium tissues was developed for investigating the molecular controls involved in the spatial deposition of minerals on collagenous tissues. Preferential mineral deposition was observed when the de-mineralized tissue sections were incubated in solutions containing a supersaturation of calcium and phosphate ions with respect to hydroxyapatite (HA). Energy dispersive X-Ray (EDX) analysis demonstrated that these minerals are likely to be octacalcium phosphate (OCP) or dicalcium phosphate dihydrate (DCPD); further characterization with a secondary technique is required to draw a more definitive conclusion. The role of collagen fibrils in mineralization was tested by removing all the non-collagenous components from the tissue sections with proteolytic enzymes and exposing them to similar mineralization conditions as the control samples. A substantially less amount of minerals were formed in these samples; this correlates well with the hypothesis in the literature that collagen fibrils alone cannot initiate mineral formation.

The silicon complexes in silicon doped calcium phosphate bioceramics have been studied using $^{29}$Si magic angle spinning nuclear magnetic resonance spectroscopy. The replacement of phosphorus by silicon in these materials requires a charge compensation mechanism which is difficult to study by many experimental techniques due to the small amount of silicon added. Producing these materials using an isotopically enriched source of silicon made the use of NMR spectroscopy feasible. Three different materials have been studied: a multiphase material commercially available under the trade name Skelite$^{\rm TM}$ composed of predominantly a silicon stabilized $\alpha$-tricalcium phosphate ($\alpha$-TCP) phase as well as a silicon doped hydroxyapatite (HA) phase, a single phase Si-HA material and a single phase silicon stabilized $\alpha$-TCP material. Slight changes to the material production method were first introduced to accommodate the switch to an isotopically enriched silicon source. Characterization of the enriched materials was carried out using Rietveld refinement of X-ray powder diffraction spectra and X-ray fluorescence spectroscopy to confirm that these materials were similar to the previously studied, non-enriched, materials in terms of the silicon contents, Ca/(P+Si) molar ratios and lattice parameters. NMR Spectroscopy showed that in all three materials, the silicon formed Q$^1$ structures in which two silicate tetrahedra joined together by sharing an oxygen, creating an oxygen vacancy which compensated the substitution of two silicon for phosphorus. This is the first observation of this charge compensation mechanism in Si-HA and may explain the interesting phase evolution previously found in the system studied in this work in which the Si-HA transforms to silicon stabilized $\alpha$-TCP upon sintering. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-12-18 14:45:38.721

Thesis (Ph. D.)--University of Adelaide, Dept. of Pathology, 1984. / Includes bibliographical references (leaves [280]-301).

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references (leaves 70-76). Online version available on the World Wide Web.