Abstract
This in vitro study evaluates the influence of pressed lithium disilicate thickness, shade and translucency on the transmitted irradiance and the Knoop microhardness (KHN) of a light-cured resin cement at two depths. One hundred and thirty-five ceramic discs of IPS e.max Press (Ivoclar Vivadent) were fabricated and divided into twenty-seven groups (n = 5) according to the association between translucency: HT (hight translucency), LT (low translucency), and MO (medium opacity); shade: BL2, A1 and A3.5; and thickness: 0.5 mm, 1.5 mm, and 2.0 mm. One side of each ceramic disc was finished, polished and glazed. The irradiance (mW/cm²) of a multiwave LED light curing unit (Valo, Ultradent) was evaluated with a potentiometer (Ophir 10ª-V2-SH, Ophir Optronics) without (control group) or with interposition of ceramic samples. The microhardness of Variolink Esthetic LC resin cement (Ivoclar Vivadent) was evaluated after 24 h at two depths (100 μm and 700 μm). Data were submitted to ANOVA followed by Tukey’s test (α = 0.05). Irradiance and KHN were significantly influenced by ceramic thickness (p < 0.0001), shade (p < 0.001), translucency (p < 0.0001) and depth (p < 0.0001). Conclusions: the interposition of increasing ceramic thicknesses significantly reduced the irradiance and microhardness of resin cement. Increased depth in the resin cement showed significantly reduced microhardness for all studied groups. Increased ceramic opacity reduced the KHN of the resin cement at both depths for all ceramic thicknesses and shades.
Highlights
Dental ceramics are used in dentistry to replace lost portions of teeth
The aim of this study was to evaluate the influence of shade, thickness, and translucency of a pressable lithium disilicate ceramic on the transmitted irradiance through the ceramic and Knoop microhardness of a resin cement
The results showed that the irradiance values were affected through different ceramic shades, translucencies and thicknesses
Summary
Dental ceramics are used in dentistry to replace lost portions of teeth. They provide significant mechanical properties that contribute to the success of dental restorations. Their wide range of indications is due to desirable characteristics, such as good biocompatibility, color stability, chemical durability, improved flexural strength, lower thermal conductivity, radiopacity, and ability to mimic function and esthetics [1,2,3,4,5]. Lithium disilicate reinforced by orthophosphate crystals in a vitreous, glassy matrix can be used in a pressed or milled form. According to the manufacturer of IPS e.max Press, a pressed lithium disilicate ceramic (Ivoclar Vivadent, Schaan, Liechtenstein), several translucencies and shade ingots are available
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