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CC BY 4.0 · Eur J Dent
DOI: 10.1055/s-0045-1809181
Original Article

Effect of Varying Sintering Speed on Optical Characteristics Alteration of Different Yttria-Doped Monochromatic Partially Stabilized Zirconia: An In Vitro Study

Atthasit Boonbanyen
1   Division of Biomaterials and Prosthodontics Research, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand
,
Niwut Juntavee 
2   Department of Prosthodontics, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand
,
Apa Juntavee 
3   Division of Pediatric Dentistry, Department of Preventive Dentistry, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand
› Author Affiliations
Funding The authors would like to acknowledge the Faculty of Dentistry, Khon Kean University, Ministry of Higher Education, Science, Research and Innovation, Royal Thai Government for the grant supporting this study (Grant Number RTG11862563).
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Abstract

Objectives

Sintering influences the color of zirconia. This study assessed the influence of varying sintering rates on optical characteristics of 3, 4, and 5 mol% yttria (Y) containing monochromatic zirconia.

Materials and Methods

A total of 135 bar specimens (width × length × thickness = 11.2 × 20 × 1.5 mm) were prepared from monochromatic 3Y, 4Y, and 5Y zirconia, and randomly sintered at regular (RS: 10°C/min), fast (FS: 35°C/min), and speed (SS: 70°C/min) sintering rate (n = 15/group). Translucency parameter (TP00), contrast ratio (CR), opalescence parameter (OP), and color difference (∆E00) were evaluated with the CIEL*a*b* system. Microstructure, crystalline [monoclinic (m), tetragonal (t), and cubic (c)] phases, and surface roughness (Ra) were evaluated by scanning electron microscope (SEM), X-ray diffraction (XRD), and three-dimensional digital microscopy.

Statistical Analysis

Analysis of variance and Bonferroni comparisons were determined for significant differences (α = 0.05).

Results

Significant differences in TP00, CR, OP, and ∆E00 upon zirconia types and sintering rates were indicated (p < 0.05). Significant increasing TP00, whereas decreasing CR and OP was shown upon increasing the Y content (5Y > 4Y > 3Y), and speeding sintering (SS ≅ FS > RS). Significant increasing ∆E00 upon increasing the Y content (5Y > 4Y > 3Y) was shown but was within an acceptable threshold (∆E00 ≤ 1.8). Ra was higher for 3Y > 4Y > 5Y. SEM indicated a larger grain for 5Y > 4Y > 3Y. XRD indicated higher t-phase in 3Y, whereas higher c-phase in 5Y.

Conclusion

Increasing translucency, whereas reducing contrast and opalescence were affected by the amount of Y content (5Y > 4Y > 3Y) and speeding sintering rate (SS ≅ FS > RS). Increasing color alteration was affected by the amount of Y content (5Y > 4Y > 3Y), but was within acceptable limits, suggesting rapid sintering rate to achieve better optical characteristics.

Keywords

color appearance - contrast - sintering rate - translucency - opalescence - zirconia


Publication History

Article published online:
21 May 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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