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Previous issue date: 2012-09-28 === The biomaterial made up of 60% hydroxyapatite (HA) and 40% beta tricalcium phosphate (β-TCP) (Bone Ceramic?, Straumann S.A. Zurich, Switzerland) is a synthetic bone graft, biocompatible, whose biphasic composition enables it to bear the bone newly formation and maintain the tissue mechanical stability. The present study has evaluated the repair in critical bone defects, made on rats calvaria, filled with that biomaterial before and after therapy with ionizing radiation. The sample was formed by 33 Wistar rats distributed into two experimental groups that received 12 Gy radiation (single dose), and a control group. In the first experimental group (N=12) the fabrication and filling of the calvaria defect were performed two weeks after radiotherapy (pos-radiotherapy group). In the second group (n=12) the fabrication and filling of the calvaria defect were performed two weeks before radiotherapy (pre-radiotherapy group). The animals in the control group (n=9) were submitted to the same surgical procedures but did not receive any ionizing radiation therapy. The animals were killed 12 weeks after surgical procedures. In all groups a close contact between the biomaterial granules and the newly formed bone tissue was observed, as well as absence of necrosis. No statistically relevant differences were detected in the histomorphological analysis of the three groups with regards to the percentage of newly formed bone tissue in the defects. There were also no differences among the groups with regards to the number of osteoblasts, osteoclasts and inflammatory cells. The VEGF (Vascular Endotelial Growth Factor) (p<0.001) immunodetection percentage, and the mineral density in the defect site (p=0.020) were higher in the control group. Thus, it can be concluded that the biomaterial made up of HA and β-TCP promotes osteoconduction in the irradiated tissue similarly to what occurs in the non-irradiated tissue. Moreover, there is no difference regarding the moment the ionizing radiation is employed, that is, whether before or after applying the biomaterial. === O biomaterial constitu?do por 60% de hidroxiapatita (HA) e 40% de beta fosfato tric?lcico (β-TCP) (Bone Ceramic?, Straumann S. A. Zurich, Su??a) ? um enxerto ?sseo sint?tico, biocompat?vel, cuja composi??o bif?sica fornece capacidade de suportar a neoforma??o ?ssea e manter a estabilidade mec?nica do tecido. No presente estudo foi avaliado o reparo em defeitos ?sseos cr?ticos, confeccionados em calv?ria de ratos, preenchidos com esse biomaterial, antes e ap?s a terapia com radia??o ionizante. A amostra foi constitu?da por 33 ratos Wistar distribu?dos em dois grupos experimentais, que receberam 12 Gy de radia??o em dose ?nica, e um grupo-controle. No primeiro grupo experimental (n=12) a confec??o e o preenchimento do defeito na calv?ria foram realizados duas semanas ap?s a radioterapia (grupo p?s-radioterapia). No segundo grupo (n=12) a confec??o e o preenchimento do defeito ?sseo ocorreram duas semanas antes da radioterapia (grupo pr?-radioterapia). Os animais do grupo-controle (n=9) foram submetidos aos mesmos procedimentos cir?rgicos, no entanto, n?o receberam terapia com radia??o ionizante. Os animais foram mortos 12 semanas ap?s os procedimentos cir?rgicos. Em todos os grupos foi observado ?ntimo contato entre o tecido ?sseo neoformado e os gr?nulos do biomaterial, bem como aus?ncia de necrose. Na an?lise histomorfom?trica n?o foram detectadas diferen?as estatisticamente significativas entre os tr?s grupos quanto ao percentual de tecido ?sseo neoformado nos defeitos. Tamb?m n?o houve diferen?as significativas entre os grupos quanto ao n?mero de osteoblastos, osteoclastos e c?lulas inflamat?rias. O percentual de imunodetec??o do VEGF (fator de crescimento endotelial vascular) (p<0,001) e a densidade mineral na regi?o dos defeitos (p=0,020) foram superiores no grupo-controle. Pode-se concluir que o biomaterial constitu?do por HA e β-TCP promove osteocondu??o no tecido irradiado de forma semelhante a que ocorre no tecido n?o irradiado. Al?m disso, n?o h? diferen?as quanto ao momento do emprego da radia??o ionizante, ou seja, se antes ou ap?s a aplica??o do biomaterial.
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