In vitro evaluation of color stability and surface properties of gingival porcelains

Batyrbekova G. In Vitro Evaluation of Color Stability and Surface Properties of Gingival Porcelains, Hacettepe University Faculty of Dentistry, Prosthetic Dentistry Program Specialization Thesis, Ankara, 2021. The aim of this in vitro study was to evaluate the effect of thermocycling on the color stability, translucency and surface roughness of two different gingival porcelain materials. Two gingival porcelains IPS e.max® Ceram Gingiva and IPS InLine Gingiva were tested. Using porcelain powders of G1, G3, G5 colors, a total of 66 disc-shaped specimens (n=11) 2×10 mm in dimension were prepared and glazed. The samples were divided into 2 groups according to the porcelain type and 3 subgroups according to their colors. The thermocycling was performed at 6000 cycles simulating an oral environment of 5 years. Color and surface roughness measurements of the samples were made before and after the thermocycling. Color measurements were made with a spectrophotometer (Konica Minolta CM 3600A, Osaka, Japan). Color change and translucency parameters were then calculated. Surface roughness (mean surface roughness [Ra; μm]) was measured using a contact profilometer (Perthometer, M1 Mahr, Göttingen, Germany). Color difference, roughness and translucency parameter (TP) data before thermocycling were evaluated with Kruskal Wallis test followed by Dunn Bonferonni paired comparison test. Two-way ANOVA in repeated measurements and pairwise comparison test with Bonferroni correction were used to evaluate the change in roughness and translucency parameter (TP) data between groups due to thermocycling. p<0.05 was considered statistically significant. Color change was below the clinically acceptable color change threshold (∆E00=2.9) and clinically perceptible color change threshold (∆E00=2.1) in all groups. After the thermocycling, the increase in roughness was statistically significant in all groups. The highest roughness increase was detected in the IPS e.max Ceram group. The change in the translucency parameters of the samples before and after the thermocycling was not statistically significant but little increase was observed in all groups. The highest translucency values were seen in G1, G3 and G5 colors, respectively. Thermal cycling caused a statistically significant increase in the roughness values (Ra) of the materials and a minimal increase in their translucency. Color change of all groups after thermocycling was less than the clinically perceptible threshold.