Resumo Muitos estudos objetivaram desenvolver biomateriais terapêuticos alternativos para o reparo ósseo. O objetivo desta revisão sistemática foi avaliar o efeito da estatina carreada por fosfato de cálcio na formação e regeneração de tecido ósseo em modelos animais quando comparado com outros biomateriais ou coágulo. Esta revisão sistemática seguiu as recomendações do Cochrane Handbook for Systematic Reviews of Interventions, PRISMA guidelines, e o Preclinical Systematic Review & Meta-analysis Facility (SyRF). O protocolo desta revisão sistemática foi registrado no PROSPERO (CRD42018091112) e no CAMARADES. Além disso, o guia ARRIVE foi utilizado com o objetivo de aumentar a qualidade e transparência do estudo. Uma pesquisa eletrônica foi realizada através do MEDLINE/PubMed, Scopus, SciELO, e biblioteca do PROSPERO. Os autores utilizaram uma estratégia de busca específica para cada base de dados, e uma busca foi conduzida na literatura cinza e nas referências dos artigos selecionados. Os critérios de elegibilidade foram estudos em animais, os quais avaliaram o repara do ósseo tratado com fosfato de cálcio como carreador de estatina. O processo de seleção obteve 8 estudos dos 657 encontrados. Todos os estudos concluíram que a aplicação local da sinvastatina carreada pelo fosfato de cálcio é biocompatível, melhora o reparo ósseo e induz uma formação óssea significantemente maior que coágulo ou fosfato de cálcio sozinho. Em conclusão, os estudos pré-clínicos pertinentes evidenciaram a biocompatibilidade do fosfato de cálcio e sua eficácia na entrega do SIM para melhorar o reparo de defeitos ósseos. Assim, estudos clínicos são encorajados a investigar o impacto do SIM associado ao enxerto ósseo de fosfato de cálcio na reparação de defeito ósseo em humanos.

Abstract Several studies have aimed to develop alternative therapeutic biomaterials for bone repair. The purpose of this systematic review was to evaluate how statins carried by calcium phosphate affect the formation and regeneration of bone tissue in animal models when compared to other biomaterials or spontaneous healing. This systematic review followed the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions, the PRISMA guidelines, and the Preclinical Systematic Review & Meta-analysis Facility (SyRF). The protocol of this systematic review was registered in PROSPERO (CRD42018091112) and in CAMARADES. In addition, ARRIVE checklists were followed in order to increase the quality and transparency of the search. An electronic search was performed using the MEDLINE/PubMed, Scopus, SciELO, and PROSPERO library databases. The authors used a specific search strategy for each database, and they also conducted a search in the grey literature and cross-references. The eligibility criteria were animal studies, which evaluated bone repair treated with calcium phosphate as a simvastatin carrier. The selection process yielded 8 studies from the 657 retrieved. All manuscripts concluded that locally applied simvastatin carried by calcium phosphate is biocompatible, enhanced bone repair and induced statistically greater bone formation than cloth or calcium phosphate alone. In conclusion, the pertinent pre-clinical studies evidenced the calcium phosphate biocompatibility and its effectiveness in delivering SIM to improve the repair of bone defects. So, clinical trials are encouraged to investigate the impact of SIM associated with calcium phosphate bone graft in repairing bone defect in humans.

Resumo Este estudo avaliou comparativamente duas configurações (pó e massa) de um biomaterial composto com base de PLGA (Poli(láctico-co-glicólico)/hidroxiapatita em nanoescala (ReOss®, Intra-Lock International) através da morfologia microscópica, citotoxicidade in vitro, biocompatibilidade e resposta in vivo como substituto ósseo. MEV e EDS caracterizaram os biomateriais antes/após o enxerto. A citocompatibilidade foi avaliada em pré-osteoblastos murinos. A osteocondutividade e a biocompatibilidade foram avaliadas em coelhos Branco da Nova Zelândia. Ambas as configurações foram implantadas na calvária de dezoito animais em defeitos não-críticos, com coágulo sanguíneo como grupo controle. Após 30, 60 e 90 dias, os animais foram eutanasiados e os fragmentos contendo os biomateriais e controles coletados. Blocos ósseos foram embebidos em parafina (n=15) destinados às análises histológica e histomorfométrica, e em resina (n=3) destinadas à MEV e EDS. Antes da implantação, a configuração massa mostrou ambas fases morfológicas porosa e fibrosa. O pó revelou partículas porosas com granulometria variável. EDS mostrou cálcio, carbono e oxigênio na configuração massa, enquanto o pó mostrou também fósforo. Após a implantação a EDS revelou cálcio, carbono e oxigênio em ambas configurações. Os materiais foram considerados citotóxicos pelo teste XTT. A análise histológica mostrou nova formação óssea e nenhuma reação inflamatória nos sítios de implante. Entretanto, a análise histomorfométrica indicou que a quantidade de osso neoformado não foi estatisticamente diferente entre os grupos experimentais. Embora ambos os materiais tenham apresentado citotoxicidade in vitro, foram biocompatíveis e osteocondutores. A configuração do ReOss® afetou as características morfológicas e a citocompatibilidade in vitro, porém não impactou a resposta biológica in vivo, como medido pelo presente modelo.

Article This study evaluated comparatively two configurations (powder and putty) of a composite biomaterial based on PLGA (Poly(lactide-co-glycolide)/nanoescale hydroxyapatite (ReOss®, Intra-Lock International) through microscopic morphology, in vitro cytotoxicity, biocompatibility and in vivo response as a bone substitute. SEM and EDS characterized the biomaterials before/after grafting. Cytocompatibility was assessed with murine pre-osteoblasts. Osteoconductivity and biocompatibility were evaluated in White New Zealand rabbits. Both configurations were implanted in the calvaria of eighteen animals in non-critical size defects, with blood clot as the control group. After 30, 60 and 90 days, the animals were euthanized and the fragments containing the biomaterials and controls were harvested. Bone blocks were embedded in paraffin (n=15) aiming at histological and histomorphometric analysis, and in resin (n=3) aiming at SEM and EDS. Before implantation, the putty configuration showed both a porous and a fibrous morphological phase. Powder revealed porous particles with variable granulometry. EDS showed calcium, carbon, and oxygen in putty configuration, while powder also showed phosphorus. After implantation EDS revealed calcium, carbon, and oxygen in both configurations. The materials were considered cytotoxic by the XTT test. Histological analysis showed new bone formation and no inflammatory reaction at implant sites. However, the histomorphometric analysis indicated that the amount of newly formed bone was not statistically different between experimental groups. Although both materials presented in vitro cytotoxicity, they were biocompatible and osteoconductive. The configuration of ReOss® affected morphological characteristics and the in vitro cytocompatibility but did not impact on the in vivo biological response, as measured by the present model.

ABSTRACT Objective: This study aimed to evaluate bone repair in rat dental sockets after implanting nanostructured carbonated hydroxyapatite/sodium alginate (CHA) and nanostructured carbonated hydroxyapatite/sodium alginate containing 5% strontium microspheres (SrCHA) as bone substitute materials. Methods: Twenty male Wistar rats were randomly divided into two experimental groups: CHA and SrCHA (n=5/period/group). After one and 6 weeks of extraction of the right maxillary central incisor and biomaterial implantation, 5 μm bone blocks were obtained for histomorphometric evaluation. The parameters evaluated were remaining biomaterial, loose connective tissue and newly formed bone in a standard area. Statistical analysis was performed by Mann-Withney and and Wilcoxon tests at 95% level of significance. Results: The histomorphometric results showed that the microspheres showed similar fragmentation and bio-absorbation (p>0.05). We observed the formation of new bones in both groups during the same experimental periods; however, the new bone formation differed significantly between the weeks 1 and 6 (p=0.0039) in both groups. Conclusion: The CHA and SrCHA biomaterials were biocompatible, osteoconductive and bioabsorbable, indicating their great potential for clinical use as bone substitutes.

Resumo O objetivo deste estudo foi avaliar a osseointegração precoce de duas superficies diferentes de implantes, uma superfície tratada com jateamento e ataque ácido (TN) comparada com outra superfície com a mesma geometria e rugosidade e modificada com hidrofilicidade / molhabilidade através do condicionamento em solução isotônica de 0,9% de cloreto de sódio (TA) através de análises histológica e histomorfométrica após a implantação em tíbia de ovelhas. Quarenta implantes dentários, divididos em dois grupos (TN e TA), foram implantados na tíbia esquerda de vinte ovelhas Santa Inês (n=5/período experimental) saudáveis e esqueleticamente maduras. Após 7, 14, 21 e 28 dias pós-implantação, as amostras foram coletadas e as ovelhas foram mantidas vivas. A análise dos cortes em resina (30 μm) permitiu a quantificação da área de osso (BA) e do contato osso-implante (BIC). O grupo TA apresentou aumento de quase 50% na BA aos 14 dias (p <0,001, ANOVA - pós teste de Tukey) em comparação com 7 dias. O grupo TA apresentou valores maiores do que o TN para BA e BIC aos 14, 21 e 28 dias após a implantação, estabilizando a cicatrização óssea. A superfície hidrofílica TA promoveu uma osseointegração precoce aos 14 e 21 dias em relação à TN, acelerando o período de cicatrização óssea após a instalação dos implantes em tíbias de ovelha.

Abstract The objective of this study was to evaluate the early osseointegration of two different implants surfaces, a sandblasted and acid-etched surface (TN) compared with same geometry and surface roughness modified to be hydrophilic/wettable by conditioning in an isotonic solution of 0.9% sodium-chloride (TA) through histological and histomorphometric analysis after sheep tibia implantation. Forty dental implants, divided in two groups (TN and TA) were placed in the left tibia of twenty healthy, skeletally mature Santa Ines sheep (n=5/experimental period). After 7, 14, 21 and 28 days post-implantation, the samples were removed and the sheep were kept alive. Analysis of resin sections (30 μm) allowed the quantification of bone area (BA) and bone-to-implant contact (BIC). TA group presented nearly 50% increase in BA at 14 days (p<0.001, ANOVA - Tukey’s post test) compared with 7 days. The TA presented higher values than the TN for BA and BIC at 14, 21, and 28 days after placement, stabilizing bone healing. TA hydrophilic surface promoted early osseointegration at 14 and 21 days compared to TN, accelerating bone healing period post-implant placement in sheep tibia.

Resumo O objetivo deste estudo foi caracterizar físico-químicamente e avaliar o reparo ósseo de discos de hidroxiapatita porosa contendo zinco após a implantação em calvária de coelhos (nZnHA). O pó de nZnHA e o pó hidroxiapatita porosa estequiométrica nanoestruturada (controle - nHA) foram confeccionados em discos (8 mm) e calcinados a 550˚C. Dois defeitos cirúrgicos foram criados na calvária de seis coelhos para a implantação dos discos. Após 12 semanas, os animais foram eutanasiados e as áreas enxertadas foram removidas, fixadas em formol a 10% e embebidas em parafina (n=10) para avaliação histomorfométrica. Além disso, uma amostra de cada grupo (n=2) foi embebida em metilmetacrilato para análise de MEV e EDS. O tratamento térmico dos discos de nZnHA transformou-os em implantes bifásicos compostos por HA contendo Zinco e β fosfato tricálcico com Zinco (ZnHA/βZnTCP). Os discos de nHA, apresentaram-se altamente cristalinos e com baixa solubilidade quando comparados aos discos de ZnHA. A análise histológica revelou que ambos os materiais foram biologicamente compatíveis e promoveram a osteocondução. As análises de FRX e MEV-EDS confirmaram a presença do zinco nas amostras de nZnHA. A avaliação histomorfométrica revelou a presença de neoformação óssea em ambos os grupos, porém sem diferenças estatísticas entre eles, com base no teste de Wilcoxon (p>0,05). O presente estudo confirmou que ambos os biomateriais otimizaram o reparo ósseo, foram biocompatíveis e osseocondutivos e a presença do zinco não favoreceu o reparo ósseo. Estudos adicionais in vivo devem ser conduzidos a fim de investigar o efeito de maiores concentrações de zinco.

Abstract The aim of this study was to characterize the physico-chemical properties and bone repair after implantation of zinc-containing nanostructured porous hydroxyapatite scaffold (nZnHA) in rabbits' calvaria. nZnHA powder containing 2% wt/wt zinc and stoichiometric nanostructured porous hydroxyapatite (nHA - control group) were shaped into disc (8 mm) and calcined at 550 °C. Two surgical defects were created in the calvaria of six rabbits (nZnHA and nHA). After 12 weeks, the animals were euthanized and the grafted area was removed, fixed in 10% formalin with 0.1 M phosphate buffered saline and embedded in paraffin (n=10) for histomorphometric evaluation. In addition, one sample from each group (n=2) was embedded in methylmethacrylate for the SEM and EDS analyses. The thermal treatment transformed the nZnHA disc into a biphasic implant composed of Zn-containing HA and Zn-containing β-tricalcium phosphate (ZnHA/βZnTCP). The XRD patterns for the nHA disc were highly crystalline compared to the ZnHA disc. Histological analysis revealed that both materials were biologically compatible and promoted osteoconduction. X-ray fluorescence and MEV-EDS of nZnHA confirmed zinc in the samples. Histomorphometric evaluation revealed the presence of new bone formation in both frameworks but without statistically significant differences (p>0.05), based on the Wilcoxon test. The current study confirmed that both biomaterials improve bone repair, are biocompatible and osteoconductive, and that zinc (2wt%) did not increase the bone repair. Additional in vivo studies are required to investigate the effect of doping hydroxyapatite with a higher Zn concentration.

ABSTRACT Objective: Based on a literature review and on our own experience, this study proposes sheep as an experimental model to evaluate the bioactive capacity of bone substitute biomaterials, dental implant systems and orthopedics devices. The literature review covered relevant databases available on the Internet from 1990 until to date, and was supplemented by our own experience. Methods: For its resemblance in size and weight to humans, sheep are quite suitable for use as an experimental model. However, information about their utility as an experimental model is limited. The different stages involving sheep experiments were discussed, including the care during breeding and maintenance of the animals obtaining specimens for laboratory processing, and highlighting the unnecessary euthanasia of animals at the end of study, in accordance to the guidelines of the 3Rs Program. Results: All experiments have been completed without any complications regarding the animals and allowed us to evaluate hypotheses and explain their mechanisms. Conclusion: The sheep is an excellent animal model for evaluation of biomaterial for bone regeneration and dental implant osseointegration. From an ethical point of view, one sheep allows for up to 12 implants per animal, permitting to keep them alive at the end of the experiments. Level of Evidence II, Retrospective Study.

Abstract The aim of this study is to evaluate the biocompatibility and osteoconductivity in surgical defects of sheep tibias filled with 1% strontium-containing nanostructured hydroxyapatite microspheres (SrHA), stoichiometric hydroxyapatite without strontium microspheres (HA), or blood clots. Santa Ines sheep were subjected to three perforations on the medial side of the left tibia. The biomaterials were characterized by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) before implantation and by X-Ray Microfluorescence (µFRX) and Scanning Electron Microscopy (SEM) after sheep tibias implantation. Surgical defects were filled with blood clots (control), SrHA (Group 1) or HA (Group 2). After 30 days, 5-µm bone blocks were obtained for histological evaluation, and the blocks obtained from 1 animal were embedded in methylmethacrylate for undecalcified sections. Mononuclear inflammatory infiltrate remained mild in all experimental groups. Giant cells were observed surrounding biomaterials particles of both groups and areas of bone formation were detected in close contact with biomaterials. All groups showed newly formed bone from the periphery to the center of the defects, which the control, HA and SrHA presented 36.4% (± 21.8), 31.2% (± 14.7) and 26.2% (± 12.9) of newly formed bone density, respectively, not presenting statistical differences. In addition, the connective tissue density did not show any significant between groups. The SrHA showing a higher volume density of biomaterial (51.2 ± 14.1) present in the defect compared to HA (32.6 ± 8.5) after 30 days (p = 0.03). Microspheres containing 1% SrHA or HA can be considered biocompatible, have osteoconductive properties and may be useful biomaterials for clinical applications.

ABSTRACT Objective The aim of this study was to investigate the in vitro and in vivo biological responses to nanostructured carbonated hydroxyapatite/calcium alginate (CHA) microspheres used for alveolar bone repair, compared to sintered hydroxyapatite (HA). Material and Methods The maxillary central incisors of 45 Wistar rats were extracted, and the dental sockets were filled with HA, CHA, and blood clot (control group) (n=5/period/group). After 7, 21 and 42 days, the samples of bone with the biomaterials were obtained for histological and histomorphometric analysis, and the plasma levels of RANKL and OPG were determined via immunoassay. Statistical analysis was performed by Two-Way ANOVA with post-hoc Tukey test at 95% level of significance. Results The CHA and HA microspheres were cytocompatible with both human and murine cells on an in vitro assay. Histological analysis showed the time-dependent increase of newly formed bone in control group characterized by an intense osteoblast activity. In HA and CHA groups, the presence of a slight granulation reaction around the spheres was observed after seven days, which was reduced by the 42nd day. A considerable amount of newly formed bone was observed surrounding the CHA spheres and the biomaterials particles at 42-day time point compared with HA. Histomorphometric analysis showed a significant increase of newly formed bone in CHA group compared with HA after 21 and 42 days from surgery, moreover, CHA showed almost 2-fold greater biosorption than HA at 42 days (two-way ANOVA, p<0.05) indicating greater biosorption. An increase in the RANKL/OPG ratio was observed in the CHA group on the 7th day. Conclusion CHA spheres were osteoconductive and presented earlier biosorption, inducing early increases in the levels of proteins involved in resorption.

Objective The objective of this study was to investigate the impact of two different commercially available dental implants on osseointegration. The surfaces were sandblasting and acid etching (Group 1) and sandblasting and acid etching, then maintained in an isotonic solution of 0.9% sodium chloride (Group 2). Material and Methods X-ray photoelectron spectroscopy (XPS) was employed for surface chemistry analysis. Surface morphology and topography was investigated by scanning electron microscopy (SEM) and confocal microscopy (CM), respectively. Contact angle analysis (CAA) was employed for wetting evaluation. Bone-implant-contact (BIC) and bone area fraction occupied (BAFO) analysis were performed on thin sections (30 μm) 14 and 28 days after the installation of 10 implants from each group (n=20) in rabbits' tibias. Statistical analysis was performed by ANOVA at the 95% level of significance considering implantation time and implant surface as independent variables. Results Group 2 showed 3-fold less carbon on the surface and a markedly enhanced hydrophilicity compared to Group 1 but a similar surface roughness (p>0.05). BIC and BAFO levels in Group 2 at 14 days were similar to those in Group 1 at 28 days. After 28 days of installation, BIC and BAFO measurements of Group 2 were approximately 1.5-fold greater than in Group 1 (p<0.05). Conclusion The surface chemistry and wettability implants of Group 2 accelerate osseointegration and increase the area of the bone-to-implant interface when compared to those of Group 1.

O coelho branco da Nova Zelândia (Oryctolagus cuniculus) é freqüentemente utilizado como modelo em estudos in vivo. Contudo, as informações referentes aos cuidados no emprego deste animal como modelo experimental são limitadas. Esta revisão da literatura pretende rever a literatura desde a seleção do modelo animal até a sua morte, enfatizando, os procedimentos para transporte, criação, reprodução, comportamento, acomodação, anestesia e manejo dos animais, de forma a racionalizar a utilização desses animais reconhecendo as características próprias dessa espécie. Conclui-se que o coelho constitui um modelo adequado e viável para cirurgia experimental.

The white New Zealand rabbit (Oryctolagus cuniculus) is frequently used as a model for in vivo studies. However, information on precautions when using this animal as an experimental model is limited. This review of the literature covers the gamut from the selection of the animal model all the way to its death, and describes procedures for transporting, raising, breeding, housing, administering anesthesia and handling so as to rationalize the utilization of this species while exploiting its unique characteristics. Based upon the literature and our own experience with white New Zealand rabbits, we conclude that the rabbit is an adequate model for experimental surgery.

OBJETIVO: Os xenoenxertos são uma alternativa aos enxertos autogênicos e devem ser osteocondutores e biocompatíveis. Um estudo recente demonstrou que as características físicas e químicas das hidroxiapatitas encontradas no comércio não são condizentes com as descrições dos fabricantes. Este estudo avalia a biocompatibilidade e a osteocondução de um xenoenxerto derivado de osso medular bovino. MÉTODOS: Quinze coelhos adultos, pesando entre 2.500g e 3.000g cada um, foram anestesiados e submetidos a procedimentos cirúrgicos para criar três perfurações na tíbia, com 2 mm de diâmetro. Esses orifícios foram preenchidos com coágulo sanguineo, Osseus® e Bio-Oss®. Os animais foram sacrificados depois de 7, 14 e 28 dias. RESULTADOS: A análise histopatológica da interface de osso e biomaterial mostrou ligeira resposta inflamatória depois de 7 dias, que esteve ausente nos períodos subsequentes. Ambos os materiais foram parcialmente substituídos por tecido ósseo diretamente em contato com a superfície dos materiais, sem ocorrência de fibrose. CONCLUSÃO: Concluímos que ambos os materiais são biocompatíveis e absorvíveis, o que permite progressiva aposição óssea na superfície durante todo o período de avaliação.

OBJECTIVE: Xenografts are an alternative to autogenous grafts and must be osteoconductive and biocompatible. A recent study has demonstrated that the physical and chemical characteristics of commercially available hydroxyapatites do not fit the manufacturers' descriptions. This study evaluates the biocompatibility and osteoconduction of a xenograft derived from bovine medullary bone. METHODS: Fifteen adult rabbits weighing between 2,500 g and 3,000 g each were anesthetized and subjected to surgical procedures to create three perforations in the tibia, with a diameter of 2 mm. These were filled with blood clot, Osseus® and Bio-Oss®. The animals were euthanized after 7, 14 and 28 days. RESULTS: Histopathological analysis of the interface between the bone and the biomaterial showed a slight inflammatory response after 7 days, which was absent in the subsequent periods. Both materials were partially replaced by bone tissue directly in contact with the surface of the materials, without the occurrence of fibrosis. CONCLUSION: We concluded that both materials are biocompatible and absorbable, allowing for progressive bone apposition on the surface throughout the evaluation period.