Ziad N Al-Dwairi, Rami Al Fodeh, Adnan Nimri, Nadin Al-Haj Husain, Abedelmalek Tabnjh
Heat-pressed zirconia-reinforced lithium disilicate demonstrated higher biaxial flexural strength than conventional lithium disilicate under the conditions of this in-vitro study, while translucency varied according to material and thickness. These findings support its potential as an alternative restorative ceramic, although further aging and clinical studies are required before confirming long-term clinical performance.
PURPOSE: Zirconia-reinforced lithium disilicate (ZLD) ceramics have been introduced to enhance the mechanical performance of conventional lithium disilicate while overcoming the machining limitations associated with milled zirconia-reinforced lithium silicate materials, thereby providing improved mechanical properties without compromising translucency. Therefore, this study aimed to compare biaxial flexural strength (BFS) and translucency parameter (TP) of the novel heat-pressed zirconia-reinforced lithium disilicate (ZLD) material (Vita Ambria) with conventional lithium disilicate (IPS e.max Press) at thicknesses mimicking veneers and crowns.
MATERIAL AND METHODS: Ninety disk-shaped specimens (Ø 13 mm) were fabricated in two thicknesses (0.5 mm and 1.2 mm) and divided into three groups (n = 30/group): IPS e.max Press, Vita Ambria High Translucent (HT), and Vita Ambria Translucent (T). TP was measured spectrophotometrically against black and white backgrounds. BFS was tested on 1.2 mm-thick specimens (n = 15/group) using a universal testing machine in accordance with ISO 6872. Data were analyzed using one-way ANOVA (BFS) and two-way ANOVA (TP), followed by Bonferroni post hoc tests (p < 0.05).
RESULTS: TP increased as thickness decreased for all materials. At 0.5 mm, Vita HT showed the highest TP (20.44 ± 0.99), followed by e.max (18.99 ± 0.83) and Vita T (17.92 ± 0.91). At 1.2 mm, e.max had the highest TP (10.88 ± 0.36), followed by Vita HT (10.09 ± 0.36) and Vita T (8.49 ± 1.19). BFS values showed significant differences among materials (P <0.001), with both Vita Ambria groups demonstrating significantly higher BFS (Vita HT: 473.38 ± 7.93 MPa; Vita T: 470.34 ± 8.62 MPa) than IPS e.max Press (438.30 ± 9.99 MPa). No significant difference was found between the two Vita Ambria translucency levels (P =1.000). Heat-pressed zirconia-reinforced lithium disilicate (Vita Ambria) demonstrated significantly superior biaxial flexural strength compared to conventional lithium disilicate (IPS e.max Press), regardless of translucency level. Translucency varied with material type and thickness, with High Translucent Vita Ambria being most aesthetic at reduced thickness (0.5 mm).
CONCLUSIONS: Heat-pressed zirconia-reinforced lithium disilicate demonstrated higher biaxial flexural strength than conventional lithium disilicate under the conditions of this in-vitro study, while translucency varied according to material and thickness. These findings support its potential as an alternative restorative ceramic, although further aging and clinical studies are required before confirming long-term clinical performance.