Effect of Cooling Rate on Mechanical Properties, Translucency, Opalescence, and Light Transmission Properties of Monolithic 4Y-TZP during Glazing

Abstract

A standard cooling rate has not been established for glazing; therefore, the effects of the cooling rate on the properties of zirconia need to be evaluated to predict outcomes in clinical practice. 4Y-TZP glazed at three different cooling rates was analyzed to estimate the effect of cooling rate during glazing on the mechanical and optical properties. Hardness tests, field-emission scanning electron microscopy analysis, X-ray diffraction analysis, flexural strength measurement, and optical property evaluations were performed. When 4Y-TZP was glazed at a higher cooling rate (Cooling-1) than the normal cooling rate (Cooling-2), there was no significant difference in grain size, flexural strength, average transmittance, and translucency parameters. The hardness was slightly reduced. The opalescence parameter was reduced for the 2.03 mm thick specimens. When 4Y-TZP was glazed at a lower cooling rate (Cooling-3) than the normal cooling rate, there was no significant difference in hardness, grain size, flexural strength, and translucency parameters. In addition, the average transmittance and opalescence parameters were slightly reduced for the 0.52 and 2.03 mm specimens, respectively. The effects of the cooling rate during glazing on the mechanical and optical properties of 4Y-TZP appear to be minimal and clinically insignificant. Therefore, even if the cooling rate cannot be strictly controlled during glazing, the clinical outcomes will not be significantly affected.

Effect of High-Speed Sintering on the Optical Properties, Microstructure, and Phase Distribution of Multilayered Zirconia Stabilized with 5 mol% Yttria

“…In yttria-stabilized zirconia (YSZ), the TP exhibited an exponential decrease as the thickness increased [ 12 , 38 ]. For A2 shade zirconia (4Y), the TP value was reported to exponentially decrease from 12.54 to 5.4 as the thickness increased from 1 mm to 2 mm [ 39 ]. The TP values of natural human dentin are approximately 7 and 21 for the incisors and molars, respectively, at a thickness of 2 mm [ 1 ].…”

“…This increase in Δb* contributed to a significant increase in the OP from the EL to DL. In YSZ, the OP value increases with increasing thickness [ 12 , 39 , 42 ]. In colored zirconia, the increase in the OP value with increasing thickness was greater than that in uncolored zirconia [ 39 , 42 ].…”

“…In YSZ, the OP value increases with increasing thickness [ 12 , 39 , 42 ]. In colored zirconia, the increase in the OP value with increasing thickness was greater than that in uncolored zirconia [ 39 , 42 ].…”

Translucent Zirconia in Fixed Prosthodontics—An Integrative Overview

“…Jeong (2022) concluded that a higher cooling rate did not result in a significant difference in grain size, flexural strength, average transmittance, and translucency, although it did lead to a slight reduction in hardness. The influence of cooling rate during the glazing process on the mechanical and optical properties of 4Y-TZP seems to be minimal and of little clinical significance [69].…”

Effects of thickness and polishing treatment on the translucency and opalescence of six dental CAD-CAM monolithic restorative materials: an in vitro study

“…Secondly, the optical properties of CAD-CAM materials may undergo changes during prosthesis repair or adjustments such as grinding or polishing [ 20 – 22 ]. Meanwhile, wear, aging, and acid etching occur naturally to the restoration [ 23 – 25 ].…”