title: Influence of surface roughness on mechanical properties of two computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials.
abstract: The aim of this study was to evaluate the influence of surface roughness on surface hardness (Vickers; VHN), elastic modulus (EM), and flexural strength (FLS) of two computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials. One hundred sixty-two samples of VITABLOCS Mark II (VMII) and 162 samples of IPS Empress CAD (IPS) were ground according to six standardized protocols producing decreasing surface roughnesses (n=27/group): grinding with 1) silicon carbide (SiC) paper #80, 2) SiC paper #120, 3) SiC paper #220, 4) SiC paper #320, 5) SiC paper #500, and 6) SiC paper #1000. Surface roughness (Ra/Rz) was measured with a surface roughness meter, VHN and EM with a hardness indentation device, and FLS with a three-point bending test. To test for a correlation between surface roughness (Ra/Rz) and VHN, EM, or FLS, Spearman rank correlation coefficients were calculated. The decrease in surface roughness led to an increase in VHN from (VMII/IPS; medians) 263.7/256.5 VHN to 646.8/601.5 VHN, an increase in EM from 45.4/41.0 GPa to 66.8/58.4 GPa, and an increase in FLS from 49.5/44.3 MPa to 73.0/97.2 MPa. For both ceramic materials, Spearman rank correlation coefficients showed a strong negative correlation between surface roughness (Ra/Rz) and VHN or EM and a moderate negative correlation between Ra/Rz and FLS. In conclusion, a decrease in surface roughness generally improved the mechanical properties of the CAD/CAM ceramic materials tested. However, FLS was less influenced by surface roughness than expected.
authors.affiliation: University of Bern, Department of Preventive, Restorative and Pediatric Dentistry, Bern, Switzerland. simon.flury@zmk.unibe.ch
authors.forename: S
authors.initials: S
authors.lastname: Flury
authors.forename: A
authors.initials: A
authors.lastname: Peutzfeldt
authors.forename: A
authors.initials: A
authors.lastname: Lussi
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D017680:Potassium Compounds / Q000737:chemistry; D017655:Silicon Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D017554:Carbon Compounds, Inorganic; C520133:IPS e.max CAD LT; D017680:Potassium Compounds; D017655:Silicon Compounds; C082340:Vita Mark II; D003776:Dental Porcelain; C016447:feldspar; C078519:leucite; C022088:silicon carbide