Repair bond strength and degradation of glass ionomer cements after mechanical and chemical challenges

Aim: Little is known about the reparability of glass ionomer cements (GICs) after storage in acid environments. The aim of this study was to evaluate the solubility and repairability of GICs immersed in acid solutions and subjected to brushing. Methods: Thirty discs of each GIC (Vitremer, VitroFil LC, VitroFil, and Maxxion R) were divided into three immersion groups: distilled water, Coca-Cola, or hydrochloric acid (HCl), then subjected to brushing. The weight of discs was measured before and after the immersions to determine mass alteration. Each disc was repaired, by adding the same brand of GIC over its surface. After immersing the repaired specimens in same solutions, shear bond strengths using universal testing machine were measured. Two-way ANOVA and Tukey's test was used (α=0.05). Results: Resin-modified GICs degrade after HCl immersion followed by brushing (p<0.05), while self-cured GICs were negatively affected by all challenges (p<0.05). The challenges decreased the repair strength for VitroFil LC (p<0.05), which had higher repair shear bond strength than the other GICs (p<0.05), exhibiting most cohesive failures. Conclusion: Self-cured GICs degraded when immersed in all acid solutions with brushing while resin-modified GICs only degraded following HCl immersion with brushing. Despite exhibiting the best repair results, VitroFil LC was the only GIC that was influenced by all the acid challenges

Implantes de diâmetros reduzidos instalados em diferentes níveis ósseos influenciam a biomecânica de próteses unitárias na região anterior maxilar? / Do narrow diameter implants installed at different bone levels influence the biomechanics of unitary prostheses in the anterior maxillary region?

O objetivo deste estudo foi avaliar a distribuição de tensão e deslocamento em implantes de diâmetro reduzido em reabilitações unitárias em região maxilar anterior, variando o posicionamento do implante (ao nível ósseo e 1,5 mm infra-ósseo), através do método de elementos finitos tridimensionais (MEF-3D). Quatro modelos 3D representando uma hemisecção do lado direito da região anterior da maxila foram simulados com a presença de coroa cimentada sobre implante (cone morse) de 10mm de comprimento, variando-se o diâmetro do implante (2,9 mm e 3,5 mm) e a instalação dos implantes no tecido ósseo em rebordo alveolar de 4,5 mm de espessura. O modelo ósseo tridimensional foi construído por recomposição tomográfica com uso dos softwares Invesalius e Rhinoceros 3D. O implante e os componentes foram modelados a partir de modificações do formato original no programa SolidWorks e finalizados no Rhinoceros, bem como o desenho da coroa simulada. A discretização dos modelos foi feita no software ANSYS 19.2, incluindo caracterização dos materiais, contatos, elaboração das malhas, condições de carregamento (178N em direção de 0, 30 e 60 graus em relação ao longo eixo do implante) e de contorno (com restrição em direção x, y, z nas secções laterais dos modelos). Os resultados mostraram comportamento biomecânico similar, com diminuição dos níveis de deslocamento e estresse para implantes de 3,5 mm e implantes infra-ósseos, muito embora os valores obtidos estiveram dentro de valores fisiológicos. Foi possível concluir que implantes de 2,9mm não foram mais favoráveis biomecanicamente que implantes de 3,5mm nas análises de deslocamento e tensão e que implantes instalados infra-ósseos favoreceram a diminuição de stress no tecido ósseo ao redor dos implantes(AU)

The Aim of this study was to evaluate the distribution of stress on implants of narrow diameter, in single unit cemented crowns in the anterior maxillary region, varying the position of the implant (at the bone level and 1.5 mm infra-osseous), through the 3D finite element analysis (3D-FEA). Four 3D models representing a right hemisection of the anterior maxillary region were simulated with the presence of a cemented crown over a 10mm long implant (morse cone), with the implant diameter varying among 2.9 mm and 3.5 mm in an simulated alveolar ridge of 4,5mm thickness. The bone of 3D models was simulated by tomographic recomposition using the software Invesalius and Rhinoceros 3D. The implant and components were modeled from modifications of the original design in the SolidWorks software and modeled in the Rhinoceros, as well as the design of the simulated crown. The discretization of the models was done in the ANSYS 19,2 software, including characterization of materials, contacts, meshes, loading conditions (178N towards 0, 30 and 60 degrees in relation to the implant long axis) and boundary conditions in the x, y, z direction in the lateral sections of the models). The results of dislodgment and von Mises showed similar maps distribution, decreasing dislodgment and stress in implants of 3,5mm diameter and in infra-osseous position, besides these results were inside physiologic values. It was possible to conclude that 2.9mm implants were no more biomechanically favorable than 3.5mm implants in the displacement and tension analyzes and that infrared implants favored the reduction of stress in the bone tissue around the implants(AU)