Fracture Toughness of a New Resin Nanoceramic CAD/CAM Material

Objectives : ��Determine the fracture toughness, Vickers Hardness, and brittleness index of a new Resin Nano Ceramic CAD/CAM material, 3M� ESPE� Lava� Ultimate CAD/CAM (LVU), compared with commercially available indirect and direct materials. �LVU contains about 79 wt% nanoceramic particles that reinforce a highly crosslinked polymeric matrix.�

Methods : �Fracture toughness was measured via the single-edge V-notched beam (SEVNB) method of ISO 6872, modified to accommodate bar sizes that could be sectioned from commercially available mill blocks. ��A V-notch was cut in 3mm x 4mm x 14mm bars, which were tested on a 3-point fixture with a 10mm span and a crosshead speed of 0.5mm/min.� Vickers hardness was measured according to ASTM C1327-08 on mounted & polished specimens (10 indents on each material).� Brittleness Index, B, was calculated from B=H_vE/K_Ic², where H_v is Vickers hardness, E is flexural modulus (reported in another study), and K_Ic is fracture toughness.� Data were analyzed via ANOVA with Tukey's t-test (p<0.05).

Results: ���

Letters in column �SND Groups� denote groups that are statistically not different (SND) via ANOVA with Tukey's t-test (p

Conclusions :�

The fracture toughness of the new resin nanoceramic material LVU is statistically higher than feldspathic glass-ceramics EMP and VM2, and composite materials MZ and TEC.� Vickers hardness of EMP and VM2 is statistically higher than LVU, MZ, and TEC.� The combination of high fracture toughness, low hardness, and low modulus makes LVU and the composite materials much less brittle than feldspathic glass-ceramics, as shown by the statistically significant differences in brittleness index.� Low brittleness may make these materials less prone to cracking during try-in and function.�