Vertical alveolar crest bone maintenance around implants in two-stage surgery: an in situ study in dogs

The aim of this study was to evaluate in situ changes in the alveolar crest bone height around immediate implant-supported crowns in comparison to tooth-supported crowns (control) with the cervical margins located at the bone crest level, without occlusal load. In Group I, after extraction of 12 mandibular premolars from 4 adult dogs, implants from Branemark System (MK III TiU RP 4.0 x 11.5 mm) were placed to retain complete acrylic crowns. In Group II, premolars were prepared to receive complete metal crowns. Sixteen weeks after placement of the crowns (38 weeks after tooth extraction), the height of the alveolar bone crest was measured with a digital caliper. Data were analyzed statistically by the Mann-Whitney test at 5% significance level. The in situ analysis showed no statistically significant difference (p=0.880) between the implant-supported and the tooth-supported groups (1.528 + 0.459 mm and 1.570 + 0.263 mm, respectively). Based on the findings of the present study, it may be concluded that initial peri-implant bone loss may result from the remodeling process necessary to establish the biological space, similar to which occurs with tooth-supported crowns.O objetivo do presente estudo foi comparar in situ modificações ocorridas na crista óssea alveolar induzidas por implantes imediatos e às induzidas por dentes naturais, ambos preparados para suportarem dispositivos protéticos situados sobre a margem óssea cervical, sem carga oclusal. No grupo I, após a extração de 12 pré-molares inferiores de 4 cães adultos, foram instalados implantes do Sistema Branemark (MK III TiU RP 4,0 x 11,5 mm) e coroas totais acrílicas. No grupo II, os pré-molares, foram submetidos a preparos convencionais, sendo cimentadas coroas totais metálicas. Após 16 semanas da instalação das coroas (38 semanas após a extração), a reabsorção da crista óssea alveolar foi avaliada in situ, por meio da mensuração das peças, com paquímetro digital. Para obtenção das medidas do grupo I, os pontos de referência foram a plataforma de assentamento do implante e a crista óssea alveolar. No grupo II, a posição do limite cervical da prótese e o início da crista óssea. Os valores obtidos foram comparados pelo teste de Mann-Whitmey com nível de significância de 5%. A média de reabsorção da crista óssea foi de 1,528 + 0,459 mm para o grupo I e de 1,570 + 0,263 mm para o grupo II, não havendo diferença estatisticamente significante (p=0,880) entre os grupos. Os resultados do presente estudo permitiram concluir que a reabsorção perimplantar inicial que ocorre na crista óssea resulta de um padrão de remodelação necessário para o estabelecimento do espaço biológico na área, assim como ocorre nos dentes naturais preparados para receberem próteses convencionais

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis of tissue response to sealing materials after furcation perforation

Objetivo: Avaliar in vivo a resposta tecidual de dentes de cães após perfuração de furca e recobrimento com Biodentine&trade;, em comparação ao MTA e à guta-percha, por meio de análise histopatológica, histoenzimológica, imunohistoquímica e por imunofluorescência. Métodos: Foram utilizados 30 dentes de 3 cães, divididos em 3 grupos: I - Biodentine; II - MTA; e III - Guta-Percha (controle). Após tratamento endodôntico e limpeza da câmara pulpar, perfurações no centro do assoalho foram realizadas intencionalmente em cada dente, as quais foram preenchidas com os diferentes materiais. Após 120 dias, os animais foram eutanasiados e as peças contendo os dentes e tecidos perirradiculares foram submetidas ao processamento histotécnico. Foram realizadas análises histopatológicas semi-quantitativas para avaliação da neoformação de tecido mineralizado e da reinserção de fibras, além de análise imunohistoquímica das proteínas osteopontina (OPN) e fosfatase alcalina (ALP) e imunofluorescência para proteína morfogenética óssea (BMP-2), proteína de adesão do cemento (CAP), sialoproteína óssea (BSP), osteocalcina (OCN) e proteína do cemento 1 (CEMP1) no tecido mineralizado neoformado e na região adjacente. Paralelamente, foi realizada a histoenzimologia para a atividade da TRAP e contagem dos osteoclastos. Os dados foram submetidos aos testes qui-quadrado e Kruskal-Wallis, com nível de significância de 5%. Resultados: Na avaliação do tecido mineralizado neoformado, o grupo controle foi significantemente diferente dos demais grupos (p0,05). Ainda, o grupo controle apresentou fibras colágenas paralelas à perfuração. Nos grupos tratados com MTA ou Biodentine também houve fibras colágenas paralelas à perfuração, porém com algumas fibras reinseridas perpendicularmente em diferentes áreas do tecido mineralizado neoformado. Todos os tratamentos induziram a expressão de OPN e ALP, porém em menor intensidade no grupo controle e em maior intensidade no grupo tratado com MTA (p0.05). In addition, the control group had collagen fibers parallel to the perforation. In the groups treated with MTA or Biodentine there were also collagen fibers parallel to the perforation, but with some fibers reinserted perpendicularly in different areas of the neoformed mineralized tissue. All materials induced OPN and ALP expression, weakest for gutta-percha and strongest for MTA (p<0.05). Only MTA induced BMP-2, BSP, OCN, CAP and CEMP1 expression. Osteoclast count was similar in the groups (p=0.97). Conclusion: Thus, according to the parameters analyzed in this present study, MTA and Biodentine presented satisfactory tissue response, with formation of mineralized tissue and partial reinsertion of fibers, and could be indicated for sealing furcation perforations. In addition, the present study elucidated some mechanisms of action by which MTA and Biodentine induce the formation of mineralized tissue, with expression of ALP and OPN mineralization markers, without interference in number of osteoclasts. Only MTA stimulated the expression of proteins associated with the formation of a cement-like mineralized tissu