Wear, strength, modulus and hardness of CAD/CAM restorative materials

Objective. To measure the mechanical properties of several CAD/CAM materials, including lithium disilicate (e.max CAD), lithium silicate/zirconia (Celtra Duo), 3 resin composites (Cerasmart, Lava Ultimate, Paradigm MZ100), and a polymer infiltrated ceramic (Enamic). Methods. CAD/CAM blocks were sectioned into 2.5 mm x 2.5 mm x 16 mm bars for flexural strength and elastic modulus testing and 4 mm thick blocks for hardness and wear testing. E.max CAD and half the Celtra Duo specimens were treated in a furnace. Flexural strength specimens (n = 10) were tested in a three-point bending fixture. Vickers microhardness (n = 2, 5 readings per specimen) was measured with a 1 kg load and 15 s dwell time. The CAD/CAM materials as well as labial surfaces of human incisors were mounted in the UAB wear device. Cusps of human premolars were mounted as antagonists. Specimens were tested for 400,000 cycles at 20 N force, 2 mm sliding distance, 1 Hz frequency, 24 degrees C, and 33% glycerin lubrication. Volumetric wear and opposing enamel wear were measured with non contact profilometry. Data were analyzed with 1-way ANOVA and Tukey post-hoc analysis (alpha = 0.05). Specimens were observed with SEM. Results. Properties were different for each material (p <0.01). E.max CAD and Celtra Duo were generally stronger, stiffer, and harder than the other materials. E.max CAD, Celtra Duo, Enamic, and enamel demonstrated signs of abrasive wear, whereas Cerasmart, Lava Ultimate, Paradigm MZ100 demonstrated signs of fatigue. Significance. Resin composite and resin infiltrated ceramic materials have demonstrated adequate wear resistance for load bearing restorations, however, they will require at least similar material thickness as lithium disilicate restorations due to their strength. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.