6533b855fe1ef96bd12b0982

RESEARCH PRODUCT

Influence of thermal tempering processes on color characteristics of different monolithic computer-assisted design and computer-assisted manufacturing ceramic materials

subject

description

Background The optical properties of dental restoration were influenced by the sintering parameters. This study investigated the effects of different tempering processes on optical properties of three monolithic Cad-Cam ceramics. Material and Methods 135 monolithic material bars (4 mm width, 14 mm length, 1.2 mm thickness) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (inCoris TZI, I), zirconia-reinforced lithium silicate (Vita Suprinity, V), and lithium disilicate glass (e.max CAD, E) ceramics, with different tempering processes through slow (S), normal (N), and fast (F) cooling (n=15). The color appearance (∆EW), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were determined. ANOVA and Bonferroni's multiple comparisons were determined for significant difference (α=0.05). The grain sizes were microscopically examined by scanning electron microscope. The phase transformation of zirconia was determined using X ray diffraction. Results The mean±sd of ΔEW, TP, CR, OP were 74.15±0.46, 1.26±0.15, 0.977±0.006, 1.02±0.12 for IS; 74.00±0.83, 1.27±0.19, 0.977±0.007, 1.02±0.12 for IN; 74.44±0.64, 1.70±0.08, 0.965±0.003, 1.30±0.07 for IF; 73.35±1.32, 2.44±0.24, 0.958±0.006, 2.10±0.20 for VS; 66.37±0.88, 4.05±0.3, 0.911±0.010, 3.18±0.20 for VN; 67.02±0.65, 3.79±0.17, 0.919±0.006, 3.01±0.13 for VF; 60.01±0.30, 5.53±0.17, 0.821±0.006, 2.71±0.06 for ES; 60.18±0.23, 5.49±0.17, 0.822±0.006, 2.66±0.05 for EN; and 59.82±0.26, 5.36±0.06, 0.826±0.002, 2.64±0.07 for EF. The color parameters were significantly affected by type of materials, tempering processes, and their interactions (p<0.05). Phase transformation from t→m related with tempering procedure for zirconia. Conclusions Rapid thermal tempering process of Y-TZP resulted in larger grain size and t→m phase transformation leading to higher translucency. To achieve optimum translucency, a fast thermal tempering process was suggested for inCoris TZI and IPS e.max CAD, whilst a normal tempering process was recommended for Vita Suprinity. Key words:Color, cooling process, contrast, opalescence, thermal tempering, translucency.