Evaluation of the color and translucency of glass-infiltrated zirconia based on the concept of functionally graded materials

Abstract

Statement of problem. Infiltrated zirconia has promising mechanical properties. However, information about its optical behavior is scarce.Purpose. The purpose of this in vitro study was to evaluate the color and translucency of zirconia submitted to infiltration and aging.Material and methods. Sixty zirconia disks were machined. Ten disks received no treatment (NT group), 10 disks were immersed in a coloring liquid (A2 group), and 10 disks were immersed in a fluorescent liquid (F group). The other 30 disks were submitted to the same treatments plus glass infiltration (NT+I, A2+I, and F+I groups). The coordinates L*, a*, and b* and the Y tristimulus values were obtained to calculate the color (Delta E-00), lightness, chroma, and hue differences; the translucency parameter (TP); and the contrast ratio (CR) associated with the specimens. After aging in an autoclave for 4 hours (T1), new measurements were made. Two- and 3-way ANOVAs were used to analyze color differences, TP, and CR. The lightness, chroma, and hue differences were evaluated by a repeated measures ANOVA. Multiple comparisons were made with the Tukey honestly significant difference (HSD) test (alpha=.05).Results. The greatest color differences were observed in the A2+I group (11.23 Delta E-00) (P<.001). Aging affected the chroma of the colored groups (P=.013 and P=.001) but did not affect their translucency (P=.347 for TP and P=.132 for CR). The greatest TP values were found in the NT and NIA groups (2.54 and 2.34, respectively), whereas the CR was equal to or close to 1 in all groups.Conclusions. Color differences were observed in the glass-infiltrated groups. The TP and CR were affected by infiltration. Aging did not influence the optical behavior of the specimens.