title: Comparison of mechanical properties of three machinable ceramics with an experimental fluorophlogopite glass ceramic.
abstract: BACKGROUND
  Fluorophlogopite glass ceramic (FGC) is a biocompatible, etchable, and millable ceramic with fluoride releasing property. However, its mechanical properties and reliability compared with other machinable ceramics remain undetermined.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare the mechanical properties of 3 commercially available millable ceramic materials, IPS e.max CAD, Vitablocs Mark II, and Vita Enamic, with an experimental FGC.
  
  
  METHODS
  Each type of ceramic block was sectioned into beams (n=15) of standard dimensions of 2×2×15 mm. Before mechanical testing, specimens of the IPS e.max CAD group were further fired for final crystallization. Flexural strength was determined by the 3-point bend test with a universal loading machine at a cross head speed of 1 mm/min. Hardness was determined with a hardness tester with 5 Vickers hardness indentations (n=5) using a 1.96 N load and a dwell time of 15 seconds. Selected surfaces were examined by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Data were analyzed by the 1-way ANOVA test and Weibull analysis (α=.05). Weibull parameters, including the Weibull modulus (m) as well as the characteristic strength at 63.2% (η) and 10.0% (B10), were obtained.
  
  
  RESULTS
  A significant difference in flexural strength (P<.001) was found among groups, with IPS e.max CAD (341.88 ±40.25 MPa)>Vita Enamic (145.95 ±12.65 MPa)>Vitablocs Mark II (106.67 ±18.50 MPa), and FGC (117.61 ±7.62 MPa). The Weibull modulus ranged from 6.93 to 18.34, with FGC showing the highest Weibull modulus among the 4 materials. The Weibull plot revealed that IPS e.max CAD>Vita Enamic>FGC>Vitablocs Mark II for the characteristic strength at both 63.2% (η) and 10.0% (B10). Significant difference in Vickers hardness among groups (P<.001) was found with IPS e.max CAD (731.63 ±30.64 H(V))>Vitablocs Mark II (594.74 ±25.22 H(V))>Vita Enamic (372.29 ±51.23 H(V))>FGC (153.74 ±23.62 H(V)).
  
  
  CONCLUSIONS
  The flexural strength and Vickers hardness of IPS e.max CAD were significantly higher than those of the 3 materials tested. The FGC's flexural strength was comparable with Vitablocs Mark II. The FGC's Weibull modulus was the highest, while its Vickers hardness was the lowest among the materials tested.
authors.affiliation: Postgraduate student, Oral Rehabilitation, Faculty of Dentistry, The University of Hong Kong, Hong Kong, PR China.
authors.forename: Brian T W
authors.initials: BT
authors.lastname: Leung
authors.affiliation: Assistant Professor, Dental Materials Science, The University of Hong Kong, Hong Kong, PR China.
authors.forename: James K H
authors.initials: JK
authors.lastname: Tsoi
authors.affiliation: Associate Professor, Dental Materials Science, The University of Hong Kong, Hong Kong, PR China.
authors.forename: Jukka P
authors.initials: JP
authors.lastname: Matinlinna
authors.affiliation: Clinical Associate Professor, Oral Rehabilitation, The University of Hong Kong, Hong Kong, PR China. Electronic address: ehnpow@hku.hk.
authors.forename: Edmond H N
authors.initials: EH
authors.lastname: Pow
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D003776:Dental Porcelain; C011254:fluorophlogopite; C023506:Glass ceramics; D015040:Zirconium