Associação do ranelato de estrôncio à enxertos ósseos bovinos mineralizados e desmineralizados: efeitos in vitro e in vivo

• Ano de defesa: 2021
• Autor(a) principal: Juliano Douglas Silva Albergaria
• Outros Autores: Gerluza Aparecida Borges Silva
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais
• Palavras-chave em Português: Biologia Celular; Regeneração Óssea; Materiais Biocompatíveis
• Link de acesso: https://hdl.handle.net/1843/52455

Bone defects are a serious problem for dental and orthopedic clinics and can be caused by different reasons, such as degenerative processes, trauma, tumors and tooth loss. Several strategies are used and studies developed for bone tissue reconstruction. Currently, mineralized bovine bone grafts (MBB) constitute one of the most used alternatives in the dental clinic. However, the use of demineralized matrices has been proposed to present collagenous and non-collagenous proteins, improving graft osteoinductivity and osteoconductivity. The use of systemic drug therapies, such as strontium ranelate (SrRan), associated with bone grafts for the treatment of fractures, has also been investigated. Therefore, at first, this work evaluated the capacity of ethylenediaminetetraacetic acid (EDTA) demineralized xenografts compared to mineralized grafts in the process of regeneration of intrabuccal bone defects in rats. The effects of grafts were evaluated after 1, 7, 14, 21 and 49 days on surgical site epithelialization and bone tissue regeneration. Evaluations were performed by standardized macrophotographs, radiography and histology. The results showed that within 7 days there was no statistical difference in the amount of granulation tissue between the groups and at 14 days, all groups had the region of the surgical site completely epithelialized. The radiographic and histological results showed that demineralized bovine bone graft (DBB) induced a greater amount of bone neoformation and mature bone. These results revealed that DBB represents an important alternative for bone reconstruction therapies in the clinic. Secondly, we evaluated the reconstruction of the proposed bone defect and its grafts by histology and radiographic tests on two methods: grayscale radiopacity and fractal analysis. Both histology and the two methods of radiographic evaluation showed a larger amount of newly formed bone for the demineralized group. However, fractal analysis did not find statistical differences in the final evaluation period. Thus, gray scale quantification appeared to be more effective when compared to fractal analysis. It is noteworthy that in the evaluation of mineralized grafts, both evaluation methods were effective. We extrapolated the tests for improving the osteoconductive and osteoinductive properties of the studied, mineralized and demineralized grafts, by means of strontium (Sr) adsorption, using in vitro tests on MC3T3-E1 cultures, and in vivo using the bone defect model studied in the periods of 1, 7, 14, 21 and 60 days. Initially, the grafts were treated with saturated SrRan solution for 14 days. The Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-OES) technique was used to evaluate the amount of Sr adsorbed in biomaterials, being significantly higher in mineralized graft. The technique also demonstrated that the mineralized graft gradually released Sr adsorbed in aqueous medium over 14 days. Cytotoxicity and cell activity tests were performed by MTT - periods of 3 and 7 days of cell culture, and Alkaline Phosphatase (AP) - periods of 7 and 10 days of cell culture, respectively. The results showed that grafts associated with Sr had greater cell viability in all periods evaluated. Regarding cellular activity, the groups treated with grafts without Sr adsorption showed better results at 7 days of cell culture. At 10 days, only the mineralized graft without Sr showed superior results in cellular activity. In in vivo experiments, macroscopic evaluations revealed a possible toxicity of Sr to the epithelium at 7 and 14 days. As for bone neoformation, evaluated by radiography and histomorphometry tests, the mineralized and demineralized grafts associated with the Sr showed high quantification of bone neoformation and maturation in the final evaluation period. These results suggest that Sr associated with xenografts favors bone deposition and does not present cytotoxicity to osteoblasts, but compromises gingival epithelialization at the studied concentrations.