An investigation on fatigue, fracture resistance, and color properties of aesthetic CAD/CAM monolithic ceramics

Ahmed Mahmoud Fouda; Osama Atta; Mutlu Özcan; Bogna Stawarczyk; Robert Glaum; Christoph Bourauel

doi:10.1007/s00784-022-04833-y

An investigation on fatigue, fracture resistance, and color properties of aesthetic CAD/CAM monolithic ceramics

Clin Oral Investig. 2023 Jun;27(6):2653-2665. doi: 10.1007/s00784-022-04833-y. Epub 2022 Dec 27.

Authors

Ahmed Mahmoud Fouda^{1

2}, Osama Atta³, Mutlu Özcan⁴, Bogna Stawarczyk⁵, Robert Glaum⁶, Christoph Bourauel⁷

Affiliations

¹ Department of Oral Technology, University Hospital Bonn, Bonn University, Welschnonnenstr. 17, 53111, Bonn, Germany. ah.foudaa@gmail.com.
² Department of Fixed Prosthodontics, Suez Canal University, Ismailia, Egypt. ah.foudaa@gmail.com.
³ Department of Fixed Prosthodontics, Suez Canal University, Ismailia, Egypt.
⁴ Division of Dental Biomaterials, Center for Dental Medicine, Clinic for Reconstructive Dentistry, University of Zurich, Zurich, Switzerland.
⁵ Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.
⁶ Institute of Inorganic Chemistry, Bonn University, Bonn, Germany.
⁷ Department of Oral Technology, University Hospital Bonn, Bonn University, Welschnonnenstr. 17, 53111, Bonn, Germany.

Abstract

Objectives: To evaluate and compare fracture resistance, translucency, and color reproducibility, as well as the effect of aging on the fracture load and color stability of novel monolithic CAD/CAM ceramics.

Materials and methods: One hundred crowns of uniform thickness were milled from five ceramic blocks (n = 20): partially crystallized lithium disilicate (PLD) and fully crystallized lithium disilicate (FLD), lithium metasilicate (LMS), 4Y-TZP (SMZ), and 5Y-TZP (UMZ) monolithic zirconia. PLD crowns were glazed, LMS was fired, and FLD was polished. SMZ and UMZ crowns were sintered and polished. Crowns were adhesively cemented to epoxy dies. Half of the crowns (n = 10) were subjected to 1.200.000 load cycles with thermal cycling. Color space values L, a, b defined by the Commission Internationale de l´Eclairage (CIELAB) were measured before and after aging, and (∆E) was calculated. Both aged and non-aged specimens were loaded until fracture in a universal testing machine and the fracture load was recorded. X-ray diffraction (XRD) and scanning electron microscope (SEM) fractographic analysis were carried out on fractured fragments of representative samples. For translucency and color reproducibility, 50 rectangular-shaped specimens were fabricated and processed as described previously. Color values were measured over black and white backgrounds, and the translucency parameter (TP) was computed. Using the shade verification mode, (∆E) to shade A3 was calculated. Data were statistically analyzed using one-way and two-way ANOVA, and t-test.

Results: Aging did not affect fracture resistance significantly (p > 0.05). The highest mean fracture load was obtained for the SMZ and UMZ. A significant color change was observed after aging in all groups. The highest TP was noted for FLD. SMZ and UMZ had the best shade match.

Conclusions: Zirconia showed higher fracture resistance and color stability than lithium silicate ceramics. Lithium silicate ceramics were more translucent. The experimental FLD demonstrated high translucency.

Clinical relevance: Tested ceramics showed sufficient stability to withstand masticatory forces. Characterization of final restorations might be mandatory for better color match.

Keywords: Aging; CAD/CAM; Color; Dental ceramics; Dental materials; Fracture resistance; Lithium disilicate; Monolithic; Prosthodontics; Translucency; Translucent zirconia.

MeSH terms

Ceramics
Color
Computer-Aided Design
Crowns
Dental Porcelain
Dental Stress Analysis
Esthetics, Dental*
Humans
Lithium*
Materials Testing
Reproducibility of Results
Silicates
Surface Properties
Zirconium

Substances

Dental Porcelain
Lithium
Silicates
Zirconium
zirconium oxide