The Optical Effect of Zirconia Background, Ceramic Thickness, and Cement on All-Ceramic Material
thesisposted on 2012-12-10, 00:00 authored by Maiko Sakai
Hypothesis: The color differences of all-ceramic restoration material would be affected relative to different zirconia abutment shades, all-ceramic thicknesses, and resin cement. Objective: To investigate the optical influence of various all-ceramic restoration material thicknesses, zirconia abutment shades and resin cement on the optical resultant color of all-ceramic restoration using a dental spectrophotometer. Methods: Heat-pressed lithium disilicate ceramic disks (IPS E.max) were fabricated in 4 different thicknesses, ranging from 0.5 to 2.0mm, and zirconia abutment disks (Atlantis) with 3.0mm thickness were fabricated in 3 different shades including the original white shade and 2 newly introduced dentine-like shades. The all-ceramic disks were placed over zirconia abutment disks with glycerin. Color measurements were made using a dental spectrophotometer (Crystaleye) for all the crown-abutment combinations with varying ceramic thickness and zirconia shades. For the evaluation of the optical effect of cement, all-ceramic disks were luted to the lightly shaded zirconia abutment disks using tooth-colored resin cement (PANAVIA) at 0.1mm film thickness, and color measurements were made with 4 different ceramic thicknesses. Three measurements were taken each time, and color differences, ∆E, ∆L*, ∆a*, and ∆b* values, were calculated with the white zirconia abutment as a control. The mean color differences were analyzed using two-way ANOVA and Tukey post hoc test (p ≤ 0.05). Results: The underlying zirconia abutment shade, ceramic thickness, and resin cement all influence the final optical color of all-ceramic restoration material (p<0.05). The zirconia abutment with the darker shade, thinner all-ceramic material, and the presence of tooth-colored resin cement resulted in larger ∆E values. The color differences with thinner all-ceramic materials were found to be well beyond the clinically acceptable threshold (∆E > 3.7), and the color differences diminished with increasing overlaying ceramic thickness. Conclusion: Careful selection of the zirconia abutment shade and luting agent with the consideration of ceramic thickness is important in obtaining optimal esthetics.
AdvisorKnoernschild, Kent L.
DepartmentDepartment of Restorative Dentistry
Degree GrantorUniversity of Illinois at Chicago