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Translucidez de diferentes espessuras de dissilicato de lítio
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Abstract(s)
Objetivo: O objetivo deste estudo consistiu na avaliação e comparação in vitro da translucidez de diferentes espessuras de dissilicato de lítio HT e LT obtidas pelo método CAD/CAM.
Materiais e Métodos: Foram sinterizados blocos de dissilicato de lítio IPS e.max CAD A3 (Ivoclar Vivadent®., Schaan, Liechtenstein), com dois níveis de translucidez, HT e LT, e posteriormente cortados em 40 espécimes quadrangulares (dimensão 15x15 mm e com quatro espessuras diferentes, 0,5 mm; 1,0 mm; 1,5 mm e 2 mm) (n=5). Foi feita a medição da translucidez através do espectrofotómetro SpectroShadeTM Micro (MHT S.p.A., Arbizzano di Negrar, Itália), que possibilitou a recolha dos resultados de acordo com o sistema de cores CIE L*a*b*, obtendo-se um valor para cada um dos parâmetros “L*”, “a*” e “b*” e, para cada espécime, foram feitas seis medições em locais distintos, sobre um fundo branco e sobre um fundo preto. Obtidos os valores, foi calculado o parâmetro de translucidez (PT) e a relação de contraste (RC), através das seguintes fórmulas: 𝑃𝑇=[(𝐿𝐵−𝐿W)2+(𝑎𝐵−𝑎𝑊)2+(𝑏𝐵−𝑏𝑊)2]12 e 𝑅𝐶=𝑌𝐵𝑌𝑊. Os dados foram analisados estatisticamente.
Resultados: Os valores médios de PT para IPS e.max CAD LT variaram entre 27,5 e 13,6. Para IPS e.max CAD HT, variaram entre 31,6 e 15,5. Com o aumento da espessura verificou-se uma diminuição no PT para ambos os materiais. Os valores médios de RC para IPS e.max CAD LT variaram entre 0,71 e 0,88. Para IPS e.max CAD HT, variaram entre 0,65 e 0,84. Com o aumento da espessura verificou-se um aumento de RC para ambos os materiais. Verificaram-se diferenças estatisticamente significativas na translucidez entre os materiais (p< 0,001) e entre as espessuras (p< 0,001). Para o PT foi identificada uma interação significativa (p=0,029) entre o tipo de material e a espessura, não se verificando o mesmo para RC (p=0,220). Foi encontrada ainda uma correlação forte e significativa entre os valores de PT e RC (ρ= -0,986, p< 0,001).
Conclusões: Com base nos resultados deste estudo, concluiu-se que espessuras mais finas apresentaram uma translucidez mais elevada. A cerâmica de dissilicato de lítio IPS e.max CAD HT apresentou uma translucidez superior à sua respetiva LT. A forte correlação encontrada entre PT e RC permitiu considerar estes dois parâmetros igualmente fiáveis na medição da translucidez de sistemas cerâmicos.
Objective: The aim of this in vitro study was to evaluate and compare the translucency of different HT and LT lithium disilicate specimens with different thicknesses, obtained by the CAD/CAM method. Materials and Methods: IPS e.max CAD A3 (Ivoclar Vivadent®., Schaan, Liechtenstein) lithium disilicate blocks, with two levels of translucency, HT and LT, were sintered, and then cut into 40 quadrangular specimens (size 15x15 mm and with four different thicknesses, 0.5 mm, 1.0 mm, 1.5 mm and 2 mm) (n = 5). The spectrophotometer SpectroShadeTM Micro (MHT S.p.A., Arbizzano di Negrar, Itália) was used to obtain the results of the CIE L*a*b*color system, obtaining a value for each of the parameters "L*", "a*"and "b*", each specimen was measured six times at different locations on a white background and on a black background. After obtaining the values, the translucency parameter (TP) and the contrast ratio (CR) were calculated, using the following formulas: 𝑇𝑃=[(𝐿𝐵−𝐿W)2+(𝑎𝐵−𝑎𝑊)2+(𝑏𝐵−𝑏𝑊)2]12 and 𝐶𝑅=𝑌𝐵𝑌𝑊. The data were analysed statistically. Results: The mean values of TP for IPS e.max CAD LT varied between 27.5 and 13.6. For IPS e.max CAD HT, they varied between 31.6 and 15.5. As the thickness increased, there was a decrease in TP for both materials. The mean values of CR for IPS e.max CAD LT varied between 0.71 and 0.88. For IPS e.max CAD HT, they varied between 0.65 and 0.84. As the thickness increased, there was an increase in CR for both materials. There were statistically significant differences in the translucency between the materials (p <0.001) and between the thicknesses (p <0.001). For TP, a significant interaction (p = 0.029) was identified between the type of material and its thickness, although the same was not observed for CR (p = 0.220). A strong and significant correlation was found between TP and CR values (ρ = -0.986, p <0.001). Conclusions: Based on the results of the present study it was concluded that thinner specimens had higher translucency. The lithium disilicate ceramic IPS e.max CAD HT showed higher translucency than the equivalent LT one. The strong correlation found between TP and CR allowed us to consider these two equally reliable parameters for measuring the translucency of ceramic systems.
Objective: The aim of this in vitro study was to evaluate and compare the translucency of different HT and LT lithium disilicate specimens with different thicknesses, obtained by the CAD/CAM method. Materials and Methods: IPS e.max CAD A3 (Ivoclar Vivadent®., Schaan, Liechtenstein) lithium disilicate blocks, with two levels of translucency, HT and LT, were sintered, and then cut into 40 quadrangular specimens (size 15x15 mm and with four different thicknesses, 0.5 mm, 1.0 mm, 1.5 mm and 2 mm) (n = 5). The spectrophotometer SpectroShadeTM Micro (MHT S.p.A., Arbizzano di Negrar, Itália) was used to obtain the results of the CIE L*a*b*color system, obtaining a value for each of the parameters "L*", "a*"and "b*", each specimen was measured six times at different locations on a white background and on a black background. After obtaining the values, the translucency parameter (TP) and the contrast ratio (CR) were calculated, using the following formulas: 𝑇𝑃=[(𝐿𝐵−𝐿W)2+(𝑎𝐵−𝑎𝑊)2+(𝑏𝐵−𝑏𝑊)2]12 and 𝐶𝑅=𝑌𝐵𝑌𝑊. The data were analysed statistically. Results: The mean values of TP for IPS e.max CAD LT varied between 27.5 and 13.6. For IPS e.max CAD HT, they varied between 31.6 and 15.5. As the thickness increased, there was a decrease in TP for both materials. The mean values of CR for IPS e.max CAD LT varied between 0.71 and 0.88. For IPS e.max CAD HT, they varied between 0.65 and 0.84. As the thickness increased, there was an increase in CR for both materials. There were statistically significant differences in the translucency between the materials (p <0.001) and between the thicknesses (p <0.001). For TP, a significant interaction (p = 0.029) was identified between the type of material and its thickness, although the same was not observed for CR (p = 0.220). A strong and significant correlation was found between TP and CR values (ρ = -0.986, p <0.001). Conclusions: Based on the results of the present study it was concluded that thinner specimens had higher translucency. The lithium disilicate ceramic IPS e.max CAD HT showed higher translucency than the equivalent LT one. The strong correlation found between TP and CR allowed us to consider these two equally reliable parameters for measuring the translucency of ceramic systems.
Description
Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas Moniz
Keywords
Translucidez Dissilicato de lítio CAD/CAM Propriedades óticas