Translucency and Biaxial Flexural Strength of Dental Ceramics

Objectives: As restorative materials, dental ceramics should have suitable translucency for excellent esthetics, and adequate strength to resist stresses. As declared by the manufactures, zirconia ceramics with improved translucency and new generation of lithium disilicate glass-ceramics have been launched into dental market, but less information is available for the translucent characteristic and mechanical properties of these materials. Therefore, the objective of the present study was to assess the translucency and flexural strengths of six dental ceramics.

Methods: Disk specimens (13 mm in diameter and 0.60 ± 0.01 mm in thickness) were prepared from following ceramics, including two lithium disilicate glass ceramics: IPS E.max Press MO1 (PMO) and IPS E.max CAD LT A2 (CLT), and four zirconia ceramics: Zenotec Bridge Trans (ZBT), Lava Standard (LVS), Lava Standard FS3 (LVF) and Lava Plus High Translucency (LVP), following the manufacturers’ instructions. A spectrophotometer was used to measure the translucency parameter (TP) of the specimens. The biaxial flexural strength was measured following the instructions of ISO 6872. TP values and biaxial flexural strength (MPa) were analyzed by one-way ANOVA, followed by Tukey’s multiple comparison test.

Results: TP values in order of most translucent to most opaque were as follows: CLT (23.9±1.0), PMO (21.8±0.4), LVP (15.0±0.2), ZNT (13.7±1.4) LVS (13.7±0.1) and LVF (13.1±0.7). There was no significant difference among ZNT, LVS and LVF (p > 0.05). Biaxial flexural strengths (MPs) from lower to higher were as follows: CLT (297±51), PMO (423±76), LVF (1289±216), LVP (1275±114), LVS (1368±200), and ZNT (1398±88). There was no significantly difference among four zirconia ceramics. (p > 0.05)

Conclusions: Two glass ceramics were significantly more translucent than zirconia ceramics, but with lower flexural strength. Among all zirconia ceramics, Lava Plus High Translucency showed improved translucency without compromising its mechanical properties.