Measurement of select physical and mechanical properties of 3 machinable ceramic materials

Objective: To measure select physical and mechanical properties of 3 machinable ceramic materials (IPS Empress CAD, Ivoclar Vivadent; Vitablocs Mark II, Vident; Paradigm C, 3M ESPE). Method and Materials: The physical and mechanical properties tested were hardness (using Vickers hardness), flexural strength and modulus (with 3-point bending), fracture toughness (with Vickers hardness indentation), and coefficient of thermal expansion (using a thermomechanical analyzer). For each of the materials, 25 specimens were fabricated to test each property, except for coefficient of thermal expansion, where n = 5. For each tested property, data were analyzed using 1-way analysis of variance and Tukey Studentized range test (significance level = .05), when required for post hoc testing. Results: Mean Vickers hardness ranged from 511.3 (SD 8.6) for Paradigm C to 569.3 (SD 10.2) for Vitablocs Mark II. Flexural strength was greatest for IPS Empress CAD at 137.51 (SD 23.34) MPa and least for Vitablocs Mark II at 94.08 (SD 14.21) MPa. Flexural modulus ranged from 8.65 (SD 2.24) GPa (Vitablocs Mark II) to 16.10 (SD 5.94) GPa (IPS Empress CAD). IPS Empress CAD had the highest fracture toughness at 2.18 (SD 0.30) MPa•m1/2, while Vitablocs Mark II had the lowest at 1.37 (SD 0.22) MPa•m1/2. Paradigm C exhibited the highest thermal expansion coefficient at 16.87 (SD 4.37) 3 10^-6/°C, and Vitablocs Mark II had the lowest at 8.60 (SD 1.47) 3 10^-6/°C. Conclusions: The 3 ceramic materials significantly differed in all of the properties measured. Vitablocs Mark II was the hardest of the 3 materials, and IPS Empress CAD had the greatest flexure strength, flexural modulus, and fracture toughness. Keywords: CAD/CAM, ceramic, machinable, properties, strength, testing