The effect of food-simulating liquids on the mechanical properties of lithium aluminosilicate glass-ceramics.

OBJECTIVES

To evaluate the impact of simulated aging with food-simulating liquids (FSLs) on the Martens hardness, indentation depth, flexural strength, and reliability of lithium aluminosilicate glass-ceramics.

METHODS

Sixty square plates (12 ×12 ×1.5 mm) were prepared from a machinable fully crystallized lithium aluminosilicate glass-ceramic (Cerec Tessera, CT), then randomly allotted to four FSL groups: artificial saliva (CT-AS), citric acid (CT-CA), ethanol (CT-ET), or heptane (CT-HP). Martens hardness (HM) and indentation depth (ID) data were obtained using a hardness tester. Biaxial flexural strength (σ) was determined using the ball-on-three-balls apparatus in a universal testing machine. Weibull analysis was used to determine the characteristic strength (σ0) and reliability (m̂U). Data for HM and σ were analysed by one-way ANOVA, Tukey's HSD, and Pearson correlations (α = 0.05).

RESULTS

FSL type had a significant effect on HM (p < 0.001, ηp2 = 0.889), ID (p < 0.001, ηp2 = 0.879), and σ (p < 0.001, ηp2 = 0.623). Minimal differences were observed between the effects of artificial saliva and heptane on HM (p = 0.914), whereas citric acid (p < 0.001) and ethanol (p = 0.001) showed significantly different effects. The highest σ0 and m̂U values were found in CT-AS (σ0 = 319.26 MPa, m̂U = 10.79), while the lowest were observed in CT-CA. A positive correlation was confirmed between HM and σ (p < 0.001, r = 0.731).

SIGNIFICANCE: Fully crystallized machinable lithium aluminosilicates exhibited adequate hardness and flexural strength after accelerated aging in artificial saliva; conversely, prolonged exposure to acidic FSLs jeopardized their mechanical properties.