Abstract
BackgroundSintering process is accountable for aesthetic appearance of zirconia restoration. This study appraised the effect of different sintering procedure via sintered temperatures and sintering times on spectral translucence of monolithic zirconia.Material and MethodsOne hundred and thirty five monolithic zirconia specimens (width, length, thickness = 10, 20, 1.5 mm) were prepared from yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP, Ceramill®) and unintentionally divided into nine groups to be sintered at different temperatures [decreasing- (SD, 1350°C), regular- (SR, 1450°C), and increasing- (SI, 1550°C) sintering temperature] and different sintering times [shortening- (HS, 60 min), regular- (HR, 120 min), and prolong- (HP, 180 min) sintering time]. Spectral translucence was determined by using spectrophotometer and calculated for translucency parameter (TP). The surface topography and grain size were evaluated by using a scanning electron microscope (SEM). Crystalline structures of monoclinic (m) and tetragonal (t) phases were determined by using the X-ray diffraction (XRD). An analysis of variance (ANOVA) was used to determine for significant differences of translucence upon different sintering processes (α=0.05).ResultsThe mean, standard deviation of TP were 3.22±0.12 for SRHP, 3.14±0.18 for SIHS, 3.04±0.17 for SRHR, 2.94±0.18 for SRHS, 2.93±0.17 for SIHR, 2.67±0.15 for SIHP, 1.91±0.17 for SDHP, 1.34±0.21 for SDHR and 0.10±0.01 for SDHS. Spectral translucence was significantly affected by altering sintering temperatures and holding times (p<0.05). Enlargement of grain size and increasing t→m phase metamorphosis related with upraising sintered temperatures and extending sintered holding times were signified.ConclusionsAltering sintering parameters affected spectral translucence of zirconia. Upraising sintered temperature to SR and prolonging sintering time to HP were advocated to enhance spectral translucence of nano-crystal monolithic zirconia, and advised to accomplished aesthetic appearance of restoration in clinical practice. Key words:CAD-CAM, sintering process, translucency, zirconia.
Highlights
The esthetic demands in dentistry have been intensifying the evolution of modern dental ceramics in the field of restorative dentistry
The difference between the groups of translucency parameter (TP) demonstrated that sintered zirconia at regular sintered-temperature caused significantly better translucency than at decreasing- and increasing-sintered temperature whereas sintered zirconia at a decreasing sintered temperature caused significantly reducing translucency than at increasing sintered temperature, as indicated in Table 3 (A) and Figure 2 (B) (p
This study indicated that translucency of nano-crystal zirconia was influenced by altering sintered procedure
Summary
The esthetic demands in dentistry have been intensifying the evolution of modern dental ceramics in the field of restorative dentistry. The solidification of zirconia may be regulated to crystalize it in t-phase by mixing yttrium-oxide (Y2O3) particles for approximately 3.5–8.7%, resulting in a modern yttrium partially stabilized tetragonal zirconia polycrystal (Y-TZP) that is competent enough to prevent generation of cracks as a result of a transformation toughening procedure, which enhances the resistance to fracture from the masticatory system in advanced reconstruction. The zirconia exhibits a white opaque color scheme with minimal translucency and requires veneering with glassy ceramic to derive a natural appearance [6]. The introduction of monolithic zirconia was aimed at elimination of the ceramic chipping problem; the possibility of achieving aesthetic appearance that can replicate the color characteristic of the natural tooth is still restricted. The light characteristic of monolithic zirconia needs to be simulated to that of the tooth structure for the restoration to derive a natural appearance. This study appraised the effect of different sintering procedure via sintered temperatures and sintering times on spectral translucence of monolithic zirconia
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