Translucent zirconia in the ceramic scenario for monolithic restorations: A flexural strength and translucency comparison test

Michele Carrabba; Andrew J Keeling; Aziz Aziz; Alessandro Vichi; Riccardo Fabian Fonzar; David Wood; Marco Ferrari

doi:10.1016/j.jdent.2017.03.002

Translucent zirconia in the ceramic scenario for monolithic restorations: A flexural strength and translucency comparison test

J Dent. 2017 May:60:70-76. doi: 10.1016/j.jdent.2017.03.002. Epub 2017 Mar 6.

Authors

Michele Carrabba¹, Andrew J Keeling², Aziz Aziz², Alessandro Vichi³, Riccardo Fabian Fonzar³, David Wood², Marco Ferrari⁴

Affiliations

¹ Department of Medical Biotechnologies, University of Siena, Siena, 53100, Italy. Electronic address: m.carrabba@yahoo.it.
² Biomaterials and Tissue Engineering Research Group, School of Dentistry, University of Leeds, Leeds, LS2 9LU, UK.
³ Department of Medical Biotechnologies, University of Siena, Siena, 53100, Italy.
⁴ Department of Medical Biotechnologies, University of Siena, Siena, 53100, Italy; Biomaterials and Tissue Engineering Research Group, School of Dentistry, University of Leeds, Leeds, LS2 9LU, UK.

PMID: 28274651
DOI: 10.1016/j.jdent.2017.03.002

Abstract

Objective: To compare three different compositions of Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) ceramic and a lithium disilicate ceramic in terms of flexural strength and translucency.

Methods: Three zirconia materials of different composition and translucency, Aadva ST [ST], Aadva EI [EI] and Aadva NT [NT](GC Tech, Leuven, Belgium) were cut with a slow speed diamond saw into beams and tabs in order to obtain, after sintering, dimensions of 1.2×4.0×15.0mm and 15.0×15.0×1.0mm respectively. Blocks of IPS e.max CAD LT were cut and crystallized in the same shapes and dimensions and used as a reference group [LD]. Beams (n=15) were tested in a universal testing machine for three-point bending strength. Critical fracture load was recorded in N, flexural strength (σ in MPa), Weibull modulus (m) and Weibull characteristic strength (σ⁰ in MPa) were then calculated. Tabs (n=10) were measured with a spectrophotometer equipped with an integrating sphere. Contrast Ratios were calculated as CR=Yb/Yw. SEM of thermally etched samples coupled with lineal line analysis (n=6) was used to measure the tested zirconia grain size. Data were statistically analyzed.

Results: Differences in translucency, flexural strength and grain size were found to be statistically significant. CR increased and flexural strength decreased in the following order ST(σ 1215±190MPa, CR 0.74±0.01)>EI(σ 983±182MPa, CR 0.69±0.01)>NT(σ 539±66MPa, CR 0.65±0.01)>LD (σ 377±39Mpa, CR 0.56±0.02). The average grain size was different for the three zirconia samples with NT(558±38nm)>ST(445±34nm)>EI(284±11nm).

Conclusions: The zirconia composition heavily influenced both the flexural strength and the translucency. Different percentages of Yittria and Alumina result in new materials with intermediate properties in between the conventional zirconia and lithium disilicate. Clinical indications for Zirconia Aadva NT should be limited up to three-unit span bridges.

Keywords: Contrast ratio; Flexural strength; Grain size; Lithium disilicate; Monolithic restoration; Translucency; Translucent zirconia; Y-TZP.

MeSH terms

Aluminum Oxide / chemistry
Ceramics / chemistry*
Dental Materials
Dental Porcelain / chemistry*
Dental Stress Analysis*
Elastic Modulus
Humans
Materials Testing
Models, Theoretical
Stress, Mechanical*
Surface Properties
Yttrium / chemistry
Zirconium / chemistry*

Substances

Dental Materials
IPS e.max CAD LT
lithia disilicate
Dental Porcelain
Yttrium
Zirconium
Aluminum Oxide
zirconium oxide
yttria