Abstract
BackgroundThe 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 Methods135 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.ResultsThe 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.ConclusionsRapid 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.
Highlights
An increase in esthetic demands and technological drive has led to the implementation of various materials with excellent physical properties [1]
Zirconia are used for restorative dentistry such as posterior crowns, bridges, and implant components because of its extraordinary mechanical properties together with its transformation toughening mechanism activated by stress induction [5, 6]
The mean, standard deviation (SD), and 95-% confidence interval of the color parameters for each group are illustrated in Table 1 and Figure 1
Summary
An increase in esthetic demands and technological drive has led to the implementation of various materials with excellent physical properties [1]. In the fabrication of esthetic zone restorations, opalescence is concerned with closely mimicking natural appearance of dental structures [22] This optical property is determined by the opalescence parameter (OP). Some alterations, such as to the fabrication processes or sintering temperature, including the addition of color modifiers, have been applied to improve the translucency and esthetics of zirconia and ceramics. These modifications affect the optical and mechanical properties of materials [23]. 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
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