Influence of thickness difference on color change of contemporary Computer Aided Designing/Computer Aided Manufacturing glass-ceramic materials

Abstract

Purpose To study the effect of thickness difference on color change of glass ceramic materials. Patients and methods Sixty three specimens were divided according to type of the material into three groups (n = 21) as follow Leucite based glass-ceramic (IPS Empress CAD), lithium disilicate based glass ceramic (IPS EMAX CAD), zirconia reinforced glass ceramic (celtra duo) and each group was further subdivided into three subgroups according to thickness (0.7, 1, 1.2 mm) seven each. The specimens were sawed by using linear precision saw, were square in shape and their dimension was 10 mm of length, 10 mm of width and three difference thicknesses (0.7, 1, 1.2 mm). The final thickness of specimens was confirmed with a digital caliper for standardization. Each group of specimens was finished according to its material manufacturer instruction, Cary 5000 Spectrophotometer provided from Agilent Technologies was used to measure color difference. One-way analysis of variance used to compare materials after glazing, multiple comparison Tukey test to compare each two materials. Results There was significant difference between all groups. At color width 0.7 and 1 mm, Celtra duo recorded the lowest color difference value while Empress recorded the highest color difference value. There was highly significant difference after glazing between materials where P value more than 0,001. At color width 0.7 and 1.2 mm, there was a highly significant difference after glazing between materials where P value is 0.001. Celtra duo showed the lowest color difference value while Emax and Empress showed equal values where P value more than 0.993. At color width 1 and 1.2 mm, Empress recorded the lowest color difference while Emax recorded the highest value. There was a highly significant difference between Emax versus Empress and Celtra duo versus Empress where P value was 0.001. On the other hand there was no significance recorded between Emax vs celtra duo where (P > 0.984). Conclusion Masking abilities of glass ceramic are affected by ceramic thicknesses, background colors. The masking ability of glass ceramics tends to improve with greater thickness, while translucency decreased.