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Doctoral Thesis
DOI
10.11606/T.82.2013.tde-23052013-091250
Document
Author
Full name
Mauricio Bordini do Amaral
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2013
Supervisor
Committee
Plepis, Ana Maria de Guzzi (President)
Alves, José Marcos
Garcia, Sergio Britto
Ishikiriama, Sergio Kiyoshi
Oliveira, Rodrigo Cardoso de
Title in Portuguese
Capacidade de regeneração óssea de biomateriais em defeito crítico de calvária: análise histológica e microtomografia computadorizada
Keywords in Portuguese
Biomateriais
Defeito crítico calvária rato
Enxerto ósseo
Hidroxiapatita
Microtomografia computadorizada
Abstract in Portuguese
O elevado número de cirurgias de enxertia óssea impulsiona o desenvolvimento de novos biomateriais de preenchimento. Materiais a base de hidroxiapatita sintética e tendão bovino mineralizado foram preparados para servirem de arcabouço para regeneração óssea. Este estudo teve como objetivo avaliar a osteocondutibilidade desses materiais, comparando-os ao Bio-Oss/Geistlich. Foram criados defeitos de tamanho crítico (circular / 8 mm) na calvária de ratos Wistar, preenchidos com os biomateriais e, após 30 dias, ocorreu o sacrifício, análise não invasiva por microtomografia computadorizada (micro-CT/ microtomógrafo SkyScan 100kV - 100'mü'A) com reconstituição de imagem em três dimensões (3D) e análise histológica convencional para avaliar a neoformação óssea e comparar os métodos. Os resultados da micro-CT mostraram que o Bio-Oss apresentou maior volume, densidade e porcentagem de tecido ósseo que os demais grupos. Nas imagens reconstituídas em 3D notou-se no grupo Bio-Oss as menores taxas de reabsorção, permanecendo em maior quantidade no interior do defeito aos trinta dias. No grupo da hidroxiapatita sintética notou-se uma intensa reabsorção do material e uma leve neoformação óssea nas margens do defeito, deixando-o com um contorno irregular. O grupo do tendão bovino mineralizado apresentou discretíssima neoformação óssea e o material foi totalmente reabsorvido. Já na avaliação da presença do material, de vasos sanguíneos e das células osteoblásticas no interior do defeito obtidos através da análise histológica, os grupos Bio-Oss e hidroxiapatita sintética obtiveram resultados semelhantes e maiores que o tendão bovino mineralizado. Constatou-se através da análise histológica que a hidroxiapatita sintética mostrou-se presente no interior do defeito exibindo propriedades osteocondutoras semelhantes a marca comercial Bio-Oss. Já o tendão bovino mineralizado não teve boa osteocondução, sendo contra-indicado na manutenção do espaço ósseo. Na comparação dos dois métodos, constatou-se que a micro-CT apresenta baixa especificidade, ou seja, não foi capaz de distinguir o tecido ósseo do Bio-Oss e alta sensibilidade, pois quantifica de uma forma muito precisa os valores com alta resolução. Já a análise histológica consegue distinguir com precisão os materiais e o tecido adjacente, porém não consegue quantificá-los de maneira fácil e precisa. Portanto, conclui-se que a hidroxiapatita sintética tem grande potencial de ser utilizada no preenchimento de defeitos ósseos, diferentemente do tendão bovino mineralizado. Quanto aos métodos de avaliação, eles são complementares e novos aprimoramentos devem ser feitos na técnica de micro-CT para melhorar sua capacidade de distinguir diferentes materiais.
Title in English
Bone regeneration in critical-size defects using hydroxyapatite, mineralized bovine tendon and Bio Oss: a three-dimensional micro-computed tomographic and histological study
Keywords in English
Biomaterial
Bone regeneration
Calvaria critical size defect
Hydroxyapatite
Micro-computed tomography ('mü'-CT)
Abstract in English
Biodegradable bone grafts have been widely employed on bone regeneration. The purpose of this study was to evaluate the osteoconductive potential of hydroxyapatite, mineralized bovine tendon and Bio-Oss/Geistlich in a rat critical-size calvaria defect model through non-destructive three-dimensional (3D) micro-tomographic ('mü'CT) imaging and histological evaluation. Two experimental biomaterials were developed: synthetic hydroxyapatite (particles size < 0,2 mm) and mineralized bovine tendon. Bio-Oss/Geistlich was employed as a control group. A critical size defect (8 mm) was created in the skull of Wistar rats (weight 200 - 300 g) and treated with the biomaterials and one group was left untreated in the control group (n = 5). After 30 days, the animals were killed and the calvaria removed for 'mü'CT and histological analysis. No adverse reactions were noted. No bone repair was observed in untreated surgical defects. The results of micro-CT showed that BioOss showed higher volume, density and percentage of bone tissue than the other groups. In the images reconstructed in 3-D was noted in the group Bio-Oss the lowest rates of resorption, staying in larger quantities within thirty days of the defect. In the group of synthetic hydroxyapatite noticed an intense resorption of the material and a slight bone formation at the margins of the defect, leaving him with an irregular contour. The bovine tendon mineralized group presented discreet bone formation and the material was completely resorbed. In the evaluation of the presence of the material, blood vessels and osteoblastic cells within the defect obtained by histological analysis, the groups Bio-Oss and synthetic hydroxyapatite showed similar results and larger than the mineralized bovine tendon. We verified by histological analysis that the synthetic hydroxyapatite is present within the defect displaying osteoconductive properties similar to trademark BioOss. Already the mineralized bovine tendon, again, did not have good osteoconduction and is contraindicated in maintaining the bone. When comparing the two methods observed that the micro-CT has low specificity, ie, was not able to distinguish the bone tissue to Bio-Oss and high sensitivity, as quantified in a very accurate values with high resolution. Already histological analysis can accurately distinguish materials and tissues, but can not quantify them easily and accurately. Therefore, we conclude that the synthetic hydroxyapatite has great potential to be used to fill bone defects, unlike mineralized bovine tendon. When comparing the methods, we found that still are complementary and new enhancements must be made in micro-CT technique to improve their ability to distinguish different materials.
 
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Publishing Date
2013-05-23
 
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