Purpose To analyze, histomorphologically, the influence of the geometry of nanostructured hydroxyapatite and alginate (HAn/Alg) composites in the initial phase of the bone repair. Methods Fifteen rats were distributed to three groups: MiHA - bone defect filled with HAn/Alg microspheres; GrHA - bone defect filled with HAn/Alg granules; and DV - empty bone defect; evaluated after 15 days postoperatively. The experimental surgical model was the critical bone defect, ≅8.5 mm, in rat calvaria. After euthanasia the specimens were embedded in paraffin and stained with hematoxylin and eosin, picrosirius and Masson-Goldner’s trichrome. Results The histomorphologic analysis showed, in the MiHA, deposition of osteoid matrix within some microspheres and circumjacent to the others, near the bone edges. In GrHA, the deposition of this matrix was scarce inside and adjacent to the granules. In these two groups, chronic granulomatous inflammation was noted, more evident in GrHA. In the DV, it was observed bone neoformation restricted to the bone edges and formation of connective tissue with reduced thickness in relation to the bone edges, throughout the defect. Conclusion The geometry of the biomaterials was determinant in the tissue response, since the microspheres showed more favorable to the bone regeneration in relation to the granules.

<p><strong>Introdução:</strong> as pesquisas com biomateriais substitutos ósseos têm crescido de forma exponencial nas últimas décadas, em todo o mundo. Estes materiais podem ser produzidos em diferentes geometrias e tamanhos de partículas que, dentre outros fatores físico-químicos, influenciam diretamente a resposta tecidual após a sua implantação <em>in vivo</em>. <strong>Objetivo:</strong> analisar a influência da diferença entre duas faixas granulométricas de microesferas de hidroxiapatita (HA) nanoestruturada associada ao alginato (HAn/alg), na fase inicial do reparo ósseo de defeito crítico, em calvária de rato. <strong>Metodologia:</strong> utilizou-se 10 ratos <em>Wistar</em>, machos, para compor os grupos experimentais: M1 – defeito ósseo preenchido com microesferas de HAn/alg, com dimensões de 250-425µm; M2 – defeito ósseo preenchido com microesferas de HAn/alg, com dimensões de 425-600µm, avaliados após 15 dias de implantação. <strong>Resultados:</strong> na análise histológica, observou-se resposta inflamatória crônica granulomatosa de permeio às microesferas, nos dois grupos, porém mais evidente no M2, no qual as microesferas mostraram fragmentação mais acentuada. Em relação ao reparo ósseo, notou-se neoformação óssea reparativa, adjacente às bordas, tanto no M1 quanto no M2. Contudo, no M1, este achado histológico foi também observado, ora circundante a algumas microesferas, ora no interior destas, principalmente daquelas localizadas próximas às margens do defeito. <strong>Conclusão:</strong> conclui-se que, na fase inicial do reparo ósseo, o tamanho da microesfera influenciou, principalmente, na disposição espacial das partículas e as microesferas de faixa granulométrica menor, de 250-425µm, apresentaram melhor arcabouço de preenchimento e distribuição ao longo do defeito, mais favoráveis à regeneração óssea, em relação às partículas de faixa granulométrica de 425-600µm.</p>

In recent decades, researchers in bone tissue bioengineering have focused on developing and improving bioceramics efficient in presenting physical-chemical characteristics similar to bone tissue, aiming to mimic cellular events and mechanisms involved in osteogenesis. Among the materials used, wollastonite (W) has stood out in recent years, mainly due to its bioactivity. Besides, tricalcium phosphate (TCP) is also used primarily due to its osteoinductivity and osteoconductivity. Given their ionic compositions and the physical-chemical properties of W and TCP, scientists have associated these two materials during the synthesis of bioceramics that unite the characteristics of each material into a single biomaterial, called composite. This design enables a variety of association that allows improvements in the biological behavior of these materials. Therefore, W/TCP composites have shown excellent performance, in vitro and in vivo, as they start to exhibit fundamental properties for bone regeneration. These characteristics indicate the use of these new biomaterials in future clinical applications, especially in cases of extensive bone losses, which remain a significant challenge for scientists and biomedical professionals. Nevertheless, despite the advances achieved, many questions must be clarified, and essential to comprehend the mechanisms involved in osteogenesis after implantation. Thus, this study aimed to contextualize the use of W/TCP composites for bone regeneration, to support further studies necessary to identify the biological behavior of these bioceramics and ensure use in clinical practice.

<div><strong>Objetivo</strong>: contextualizar, por meio de revisão de literatura, a utilização dos nanobiomateriais para a regeneração óssea, na últimadécada. <strong>Metodologia</strong>: Selecionaram-se artigos originais publicados na base de dados online US National Library of Medicine National Institutes of Health (PubMed), mediante os filtros Clinical trial, full text, published in the last 10 years. <strong>Resultado</strong>: Dos 18 artigos selecionados na busca, 16 foram utilizados para compor esta revisão. <strong>Conclusão</strong>: Os ensaios clínicos têm demonstrado que os biomateriais nanoestruturados podem acelerar o mecanismo de regeneração óssea e potencializar a angiogênese e a osteogênese. Diante do exposto, o presente trabalho reforça a importância do contínuo desenvolvimento das pesquisas na Bioengenharia Tecidual Óssea, visando a uma melhor compreensão dos fatores morfológicos e físico-químicos de um nanobiomaterial destinado à regeneração óssea.</div>

This study analyzes the clinical, macroscopic and radiographic characteristics of a biomaterial with different proportions of wolastonite (W) and tricalcium phosphate (TCP) on bone tissue regeneration during the implantation process of an experimental model of critical bone defects. Fifteen Wistar rats were used, randomly distributed in 5 groups (n = 3), with a bone defect created on an 8.0 mm diameter calvaria. 4 groups received implants with different proportions of W%/TCP%, referred to as W20/TCP80, W40/TCP60, W60/TCP40 and W80/TCP20. The fifth control group (GC) was filled with blood clot only. Clinical evaluation was performed every 24 hours, and after 7 days, the animals were euthanized. The calvaria were dissected and analyzed macroscopically and by radiography. All study groups showed a satisfactory clinical evolution. The macroscopic analysis showed filling of the bone defect with granules surrounded by newly formed tissue, and the radiographic analysis showed different patterns of displacement of the biomaterial. The study concluded that the different proportions of W%/TCP% were well tolerated by the study groups and demonstrated biocompatibility. The enhanced hydrophilic behavior of the W40/TCP60, W60/TCP40 and W80/TCP20 groups favored the application in the experimental model in vivo.

Purpose: To evaluate, through histomorphometric analysis in critical bone defect, the osteogenic behavior of new glass-ceramic biomaterials in granules, named different from pseudowollastonite (p-W) and beta tricalcium phosphate (β-TCP). Methods: Forty Wistar rats were randomly distributed into 4 groups, with 5 animals in each group recovered at 15 and 45 days: G20/80 (20% p-wollastonite and 80% β-tricalcium phosphate); G60/40 (60% p-W and 40% β-TCP); G80/20 (80% p-W and 20% β-TCP); and CG (control group). Results: A histomorphological analysis showed that, in all rules, the composites were biocompatible and bioactive. The G60/40 presents osteoid matrix deposition in 65% of the bone defect at 45 days. While the other groups formed similar percentages of bone neoformation in both biological points. Conclusion: The studied composites are biocompatible, fillers and osteoconductive.