Strength-limiting damage and its mitigation in CAD-CAM zirconia-reinforced lithium-silicate ceramics machined in a fully crystallized state

Copyright © 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved..

OBJECTIVES: The objective was to explore how clinically relevant machining process and heat treatment influence damage accumulation and strength degradation in lithium silicate-based glass ceramics machined in the fully crystallized state.

METHODS: A commercial zirconia-reinforced lithium silicate (ZLS) glass ceramic with a fully developed microstructure (Celtra® Duo) was studied. Disk-shaped specimens (nominal 10 mm diameter and 1 mm thickness) were fabricated either using a CAD-CAM process, creating a clinically relevant dental restoration surface, or were sectioned from water-jet cut cylindrical blocks with their critical surfaces consistently polished. Bi-axial flexure strength (BFS) was determined in a ball-on-ring configuration, and fractographic analysis was performed on failed specimens. XRD, AFM and SEM measurements were conducted before and after heat treatment. For each sample group, BFS was correlated with surface roughness. A two-way ANOVA and post-hoc Tukey tests were used to determine differences in BFS between machining and heat treatment groups (ɑ = 0.05).

RESULTS: A two-way ANOVA demonstrated that BFS was influenced by fabrication route (p < 0.01) with CAD-CAM specimens exhibiting significantly lower mean BFS. A factorial interaction was observed between heat treatment and machining route (p < 0.01), where a significant strengthening effect of post-manufacture heat treatment was noted for CAD-CAM specimens but not sectioned and polished samples. CAD-CAM specimens exhibited sub-surface lateral cracks alongside radial cracks near fracture origin which were not observed for polished specimens. BFS did not correlate with surface roughness for polished specimens, and no change in microstructure was detectable by XRD following heat treatment.

SIGNIFICANCE: The mechanical properties of the ZLS ceramic material studied were highly sensitive to the initial surface defect integral associated with manufacturing route and order of operations. CAD-CAM manufacturing procedures result in significant strength-limiting damage which is likely to influence restoration performance; however, this can be partially mitigated by post-machining heat treatment.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:36

Enthalten in:

Dental materials : official publication of the Academy of Dental Materials - 36(2020), 12 vom: 15. Dez., Seite 1557-1565

Sprache:

Englisch

Beteiligte Personen:

Romanyk, Dan L [VerfasserIn]
Guo, Yilan [VerfasserIn]
Rae, Nyssa [VerfasserIn]
Veldhuis, Sydney [VerfasserIn]
Sirovica, Slobodan [VerfasserIn]
Fleming, Garry Jp [VerfasserIn]
Addison, Owen [VerfasserIn]

Links:

Volltext

Themen:

12001-21-7
9FN79X2M3F
Annealing
Bi-Axial flexure strength
C6V6S92N3C
CAD-CAM
Dental Porcelain
Glass-Ceramic
Journal Article
Lithium
Research Support, Non-U.S. Gov't
S38N85C5G0
Silicates
Zirconia reinforced lithium silicate
Zirconium
Zirconium oxide

Anmerkungen:

Date Completed 17.12.2020

Date Revised 17.12.2020

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1016/j.dental.2020.09.012

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM315902140