Coldea A, Donmez MB, Stawarczyk B. Effect of final temperature and heating rate on the mechanical and optical properties of a zirconia veneering ceramic.
J Mech Behav Biomed Mater 2024;
149:106235. [PMID:
37976995 DOI:
10.1016/j.jmbbm.2023.106235]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 11/07/2023] [Accepted: 11/08/2023] [Indexed: 11/19/2023]
Abstract
PURPOSE
To evaluate the effect of firing temperature and heating rate on the volumetric shrinkage, translucency, flexural strength, hardness, and fracture toughness of a zirconia veneering ceramic.
MATERIAL AND METHODS
Zirconia veneering ceramic specimens (N = 45) with varying final temperatures (730 °C, 750 °C, and 770 °C) and heating rates (70 °C/min, 55 °C/min, and 40 °C/min) were fabricated (n = 5). Each specimen's shrinkage, translucency, flexural strength, hardness, and fracture toughness were determined. Two-way analysis of variance, Scheffé test, and Pearson's correlation analysis were used to evaluate data (α = 0.05).
RESULTS
The shrinkage (44.9 ± 3.1-47.5 ± 1.6 vol%) and flexural strength (74.1 ± 17.4-107.0 ± 27.1 MPa) were not affected by tested parameters (P ≥ 0.288). The interaction between the main factors affected the translucency, hardness, and fracture toughness of the specimens (P ≤ 0.007). Specimens with 770 °C final temperature and 70 °C/min heating rate had the lowest (21.8 ± 3.2 %) translucency (P ≤ 0.039). The hardness ranged between 4.98 ± 0.51 GPa (730 °C; 70 °C/min) and 5.60 ± 0.37 GPa (770 °C; 70 °C/min). Fracture toughness ranged between 0.54 ± 0.04 MPa√m and 0.67 ± 0.08 MPa√m with the highest values for specimens fired at 730 °C with 70 °C/min (P ≤ 0.001). There was a positive correlation between translucency and hardness (r = 0.335, P = 0.012), and a negative correlation between fracture toughness and all parameters other than shrinkage (translucency: r = -0.693/P < 0.001, flexural strength: r = -0.258/P = 0.046, hardness: r = -0.457/P < 0.001).
CONCLUSIONS
Heating rate and final temperature should be considered while fabricating veneered zirconia restorations with tested ceramic as they affected the translucency, hardness, and fracture toughness.
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