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OBJECTIVE: To evaluate the effect of the deterioration of computer aided design/computer aided manufacturing (CAD/CAM) burs during zirconia milling, on surface roughness, contact angle, and fibroblast viability. MATERIALS AND METHODS: Ceramic blocks were milled and 75 ceramic disks (8 × 1.5 mm) made and allocated into three groups (n = 25): G1-brand new 2L and 1L burs, G2-2L bur at the end of lifetime and brand new 1L bur and G3-both burs at the end of their lifetimes. Roughness (Ra, Rq, and Rz) was evaluated using a 3D optical profilometer, the contact angle by the sessile drop method and the cell viability of the mouse NIH/3T3 fibroblast, using the Alamar Blue assay at intervals of 24, 48, and 72 h (ISO 10993-5). Data were analyzed by one-way ANOVA and Kruskal-Wallis tests (p ≤ 0.05). RESULTS: Roughness increased as the burs deteriorated and G3 (0.27 ± 0.04) presented a higher value for Ra (p < 0.001). The highest contact angle was observed in G3 (86.2 ± 2.66) when compared with G1 (63.7 ± 12.49) and G2 (75.3 ± 6.36) (p < 0.001). Alamar Blue indicated an increase in cell proliferation, with no significant differences among the groups at 24 and 72 h (p > 0.05). CONCLUSIONS: The deterioration of the burs increased the surface roughness and decreased the wettability, but did not interfere in cell viability and proliferation. CLINICAL SIGNIFICANCE: The use of custom zirconia abutments represents an effective strategy for single crowns restorations. Our findings suggest that these abutments can be efficiently milled using CAD/CAM burs within their recommended lifetime.

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Commercial Yttria-tetragonal zirconia polycrystalline (Y-TZP) was subjected to surface treatments, and the bond strength of dual resin cement to Y-TZP and failure modes were evaluated. Disks (12 mm × 2 mm), cylinders (7 mm × 3.3 mm), and bars (25 mm × 5 mm × 2 mm) were milled from Y-TZP CAD-CAM blocks, divided into seven groups, and subjected to different surface treatments; silicatization was used as control. On the basis of the literature, this study evaluated modifications with films containing SiO2 nanoparticles and silane; SiO2+ZrO2­SiO2 (50%) and ZrO2 (50%) nanoparticles, SiO2+ZrO2/Silane-SiO2 (50%) and ZrO2 (50%) nanoparticles, and silane. Specimens were analyzed by wettability (n = 3), surface free energy (n = 3), X-ray diffraction (n = 1), Fourier transform infrared spectroscopy (FTIR) (n = 1), roughness (n = 5), shear bond test (n = 10), and dynamic modulus (n = 3). Specimens treated with hydrofluoric acid­HF 40% presented significantly higher contact angle and lowest surface free energy (p < 0.05). The SiO2/Silane presented crystalline SiO2 on the surface. The surface roughness was significantly higher for groups treated with nanofilms (p < 0.05). Shear bond strength was significantly higher for silicatization, HF 40%/silicatization, SiO2/Silane, and SiO2+ZrO2/Silane groups. The proposed treatments with nanofilms had potentially good results without prejudice to the physicochemical characteristics of zirconia. Generally, groups that underwent silica surface deposition and silanization had better bond strength (p < 0.005).

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ABSTRACT Introduction: Various surface pre-treatment methods have been adapted to optimize the bonding between the zirconia ceramics and the orthodontic brackets. Objective: This review is aimed at systematically analyzing the relevant data available in the literature, to find out the most effective and durable bonding protocol. Methods: Database search was conducted in PubMed, Scopus, and ScienceDirect, during September 2020. The review was conducted according to the PRISMA guidelines. Results: Based on the inclusion criteria, 19 articles were selected for qualitative analysis. Meta-analysis could not be performed due to the heterogeneity of the methodology among the studies. Most of the studies scored medium risk of bias. Compared to the untreated surface, surface pretreatments like sandblasting and lasers were advantageous. Primers and universal adhesive were mostly used as an adjunct to the mechanical pretreatment of the zirconia surface. In most studies, thermocycling seemed to lower the shear bond strength (SBS) of the orthodontic brackets. Conclusion: Based on this qualitative review, surface pretreatments with lasers and sandblasting can be suggested to optimize the bracket bond strength. To clarify this finding, meta-analysis is anticipated. Hence, high heterogeneity of the included studies demands standardization of the methodology.

RESUMO Introdução: Diferentes métodos de pré-tratamento da superfície foram adaptados para otimizar a colagem entre os braquetes ortodônticos e as cerâmicas de zircônia. Objetivo: A presente revisão teve como objetivo analisar, de forma sistemática, os dados relevantes na literatura, para buscar o protocolo de colagem mais efetivo e duradouro. Métodos: As buscas foram feitas em setembro de 2020, nas seguintes bases de dados: PubMed, Scopus e ScienceDirect. A revisão foi feita de acordo com as diretrizes do PRISMA. Resultados: Com base nos critérios de inclusão, 19 artigos foram selecionados para análise qualitativa. A metanálise não pôde ser feita, devido à heterogeneidade na metodologia dos estudos incluídos. A maior parte dos estudos apresentou risco de viés moderado. Comparadas às superfícies não tratadas, as superfícies com pré-tratamento usando jateamento ou laser apresentaram vantagem. Primers e adesivos universais foram mais usados como adjuntos ao pré-tratamento mecânico da superfície de zircônia. Na maioria dos estudos, a termociclagem parece ter reduzido a resistência ao cisalhamento dos braquetes ortodônticos. Conclusões: Com base nessa revisão qualitativa, os pré-tratamentos de superfície com laser e jateamento podem ser sugeridos para otimizar a resistência ao cisalhamento dos braquetes. Para esclarecer esse achado, uma metanálise é necessária. Para isso, faz-se necessária a padronização da metodologia, para lidar com a alta heterogeneidade dos estudos incluídos.

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Objetivo: Investigar o efeito de técnicas de acabamento/polimento, da espessura e do envelhecimento in situ na resistência à flexão, topografia superficial e adesão celular de uma zircônia ultratranslúcida. Metodologia: Duzentas e quarenta barras de zircônia (UT: Prettau Anterior/Ultratranslúcida, Zirkonzahn, Gais, Itália) foram cortadas, lixadas e sinterizadas, sendo metade (120) nas dimensões finais de 8 x 2 x 1mm e as demais nas dimensões de 8 x 2 x 0,5mm. As barras foram divididas em 16 grupos (n=15) de acordo com três fatores: "envelhecimento in situ" (E: com e sem), "espessura"(1: 1 mm ou 05: 0,5mm) e "Acabamento e Polimento" (C: Controle; B:borrachas DhPro, Paraná Brasil; P: Asperização com pontas diamantadas KG Sorensen 4135; PB: Asperização com pontas diamantadas + Pontas de borrachas ). Para os grupos experimentais submetidos ao envelhecimento in situ, foram selecionados 15 pacientes (comitê de ética - 3.133.187), as amostras foram incluídas nas próteses totais provisórias dos pacientes, que utilizaram as próteses com as barras durante 60 dias. As barras foram submetidas ao ensaio de mini flexão de três pontos (1mm/min, 100 kgf). Duas amostras de cada grupo foram preparadas para as análises topográficas em Microscopia Eletrônica de Varredura (MEV), Difração de raios X (DRX), Microscopia de Força Atômica (AFM) e rugosidade superficial. Para o ensaio de adesão celular, seis blocos de zircônia ultra translúcida (2,5 x 2,5 mm), de cada grupo, foram contaminadas com C. albicans (ATCC 90028) para contagem da unidade formadora de colônia (UFC/mL). Os dados do ensaio de mini flexão (MPa) foram analisados por meio de ANOVA (3 fatores) e Tukey (5%); e os dados do ensaio de adesão celular pelo teste Kruskal Wallis (5%). Resultados: ANOVA (3 fatores) revelou que apenas o fator "Acabamento e Polimento" foi estatisticamente significativo para a resistência à mini flexão (p=0,0001). O desgaste apenas com broca diamantada produziu valores de resistência à mini flexão (variando de 257,1 a 292,9MPa) estatisticamente inferiores em relação aos grupos polidos apenas com discos de borracha (variando de 449,8 a 513,5 MPa), para todas as condições experimentais. No que diz respeito à adesão celular, o teste de Kruskal wallis não revelou diferenças significativas entre os grupos experimentais (p=0,053), apesar da rugosidade ter sido estatisticamente significante por meio do ANOVA (p = 0,001) e diferente entre todos os grupos. Conclusão: O ajuste de peças monolíticas de zircônia ultratranslúcida deve ser realizado idealmente com discos de borracha de poliuretano impregnadas com diamantes. Para a adesão celular, os protocolos de acabamento e polimento não interferem na adesão fúngica, apenas na rugosidade superficial, sendo as amostras polidas com borrachas as de maior lisura (AU).

Introduction: The aim of this study was to investigate the influence of different protocols of finishing and polishing, thickness, and aging in situ on flexural strength and cell adhesion of ultratranslucent zirconia. Methodology: 240 zirconia bars (UT: Prettau Anterior/Ultratranslucent, zirkonzahn, Gais, Italy) were cut, polished and sintered, presenting final dimensions of 1,0 x 2 x 8mm, and 0,5 x 2 x 8mm. The bars were divided among 16 groups (n=15) in accordance to three factors "in situ aging"­ 2 levels (With and Withouth "E"), "thickness" ­ 2 levels (1- 1 mm or 05- 0,5mm) and "Finishing and Polishing" ­ 4 levels (CControl, B- Rubber polishing; P- grinding with burs; PB- grinding with burs + polishing). To the experimental groups submitted to in situ aging, 15 patients were selected (ethics commitee - 3.133.187), the samples were included on the temporary prothesis, and the patients used the prothesis with the bars during 60 days. The bars were submitted to mini flexure three points test (1mm/min, load cell 100 kgf). Two samples of each group were prepared to the topographical analysis on Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and surface roughness. For the cell adhesion assay, six blocks of ultratranslucent zirconia (2.5 x 2.5 mm), of each group were contaminated with the C. albicans (ATCC 90028) for counting the colony forming units (CFU / mL). Results: The mechanical test results were analyzed using ANOVA (3 factors) and Tukey (5%); and the cell adhesion assay data by the Kruskal Wallis test (5%. Results: ANOVA (3 factors) revealed that only the "Finishing and Polishing" factor was statistically significant for mini-flexure strength (p = 0.0001). The finishing and polishing with rubber polishers produced mini-flexure resistance values (varying from 257,1 to 292,9 Mpa) statistically lower in relation to the groups polished only with rubber discs (varying from 449,8 to 513,5 Mpa) to all experimental conditions. Concerning to cell adhesion, Kruskal wallis test did not reveal any significant differences between the experimental groups (p=0,053), despite of the fact that, the surface roughness presented itself statistically significant through ANOVA (p = 0,001) and difference between all groups. Conclusion: The adjustment of ultratranslucent zirconia monolithic should preferably be performed with rubber polishers impregnated with polyurethan. Concerning to cell adhesion, the protocols of finishing and polishing do not interfer at fungal adhesion, only on surface roughness, when the samples are polished with the smoothest rubbers (AU).

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