Strength and phase transformation of different zirconia types after chairside adjustment

Awab Abdulmajeed; Taiseer A Sulaiman; Aous A Abdulmajeed; Timo O Närhi

doi:10.1016/j.prosdent.2022.06.015

Strength and phase transformation of different zirconia types after chairside adjustment

J Prosthet Dent. 2022 Aug 5:S0022-3913(22)00422-X. doi: 10.1016/j.prosdent.2022.06.015. Online ahead of print.

Authors

Awab Abdulmajeed¹, Taiseer A Sulaiman², Aous A Abdulmajeed³, Timo O Närhi⁴

Affiliations

¹ Assistant Professor, Department of General Practice and Prosthodontics, School of Dentistry, Virginia Commonwealth University, Richmond, Va; Doctoral student, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.
² Associate Professor, Division of Comprehensive Oral Health, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC. Electronic address: sulaiman@unc.edu.
³ Associate Professor, Department of General Practice and Prosthodontics, School of Dentistry, Virginia Commonwealth University, Richmond, Va.
⁴ Professor, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland; Welfare Division, Turku, Finland.

PMID: 35934577
DOI: 10.1016/j.prosdent.2022.06.015

Abstract

Statement of problem: Limited evidence is available for the effect of chairside adjustment using diamond instruments on different types of zirconia.

Purpose: The purpose of this in vitro study was to evaluate the effect of simulated adjustments on the biaxial flexural strength and phase transformation of 3 different zirconia types.

Material and methods: Three zirconia types from the same manufacturer (Katana; Kuraray) were used: High Translucency (3Y-PSZ), Super Translucent Multi Layered (4Y-PSZ), and Ultra Translucent Multi Layered (5Y-PSZ). Thirty disk-shaped specimens (Ø14×1.2 mm) were fabricated according to the International Organization for Standardization (ISO) Standard 6872 from different zirconia types (N=90). Specimens were either left without adjustment (NA), adjusted with Dialite ZR finishing and polishing system (Brasseler) (APol), or adjusted with course diamond instruments only (ADia). The specimens were distributed into 9 groups (n=10): group 3Y-PSZ/NA, group 3Y-PSZ/APol, group 3Y-PSZ/ADia, group 4Y-PSZ/NA, group 4Y-PSZ/APol, group 4Y-PSZ/ADia, group 5Y-PSZ/NA, group 5Y-PSZ/APol, and group 5Y-PSZ/ADia. The biaxial flexural strength of each specimen was measured by using a universal testing machine (Model 4411; Instron) and according to ISO 6872. X-ray diffraction analysis was conducted to quantify the monoclinic phase transformation. Scanning electron microscopy images were obtained to evaluate the fracture pattern. Statistical analysis was performed by using analysis of variance (ANOVA) and Tukey multiple comparison tests for pairwise comparisons (α=.05).

Results: The mean biaxial flexural strengths ranked from the highest to the lowest were for 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ under any test condition (P=.007). Chairside adjustment with a diamond instrument significantly decreased the flexural strength of all zirconia types (P<.05). No statistically significant difference was found between the effect of APol and ADia on the strength of zirconia 3Y-PSZ (P=.603), 4Y-PSZ (P=.993), and 5Y-PSZ (P=.660). Phase transformation did not occur in the 5Y-PSZ groups. ADia groups had significantly higher phase transformation values regardless of zirconia type (P<.05).

Conclusions: The biaxial flexural strength of zirconia decreased significantly after chairside adjustment with diamond instruments regardless of the yttria percentage. Adjustment with the Dialite ZR finishing and polishing system caused less tetragonal to monoclinic phase transformation than adjustment with a course-grit diamond instrument.