title: Resistance to staining, flexural strength, and chemical solubility of core porcelains for all-ceramic crowns.
abstract: OBJECTIVE
  The increased demand for tooth-colored restorations has prompted the use of ceramics in areas that are subject to masticatory stresses. To maximize the strength of these restorations, manufacturers and clinicians advocate placement of core materials in lieu of veneering materials in areas that are more susceptible to fracture. The objectives of this study were to determine the: resistance to staining of three core porcelains used for all-ceramic restorations, Procera, IPS Empress, and In-Ceram, through the use of colorimetry and visual observation; flexural strength of these porcelains under a three-point bend test; and chemical solubility in a controlled environment.
  
  
  METHODS
  L*a*b* values were obtained for each specimen before and after immersion in a saturated solution of methylene blue in ethanol for 24 hours. Visual observation was also performed to ascertain color differences before and after staining. A three-point bend test was used to determine flexural strength. A reflux-condenser type, three-piece extraction apparatus was used with 4% acetic acid solution for 16 hours to determine solubility. Each sample was weighed before and after the reflux procedure to ascertain percentage weight loss.
  
  
  RESULTS
  The mean delta E obtained for IPS Empress was 14.5; In-Ceram was 9.2, and Procera was 9.0. Flexural strength obtained for IPS Empress, In-Ceram, and Procera was 176.9 MPa, 323.4 MPa, and 464.3 MPa, respectively. Weight loss of IPS Empress, In-Ceram, and Procera was 0.056%, 0.734%, and 0.003%, respectively.
  
  
  CONCLUSIONS
  IPS Empress showed the least resistance to staining. IPS Empress had the lowest flexural strength, while Procera had the highest. In-Ceram demonstrated the highest chemical solubility.
authors.affiliation: Department of Prosthodontics, University of Florida College of Dentistry, Gainesville, USA. jesquivel@dental.ufl.edu
authors.forename: J F
authors.initials: JF
authors.lastname: Esquivel-Upshaw
authors.forename: J
authors.initials: J
authors.lastname: Chai
authors.forename: S
authors.initials: S
authors.lastname: Sansano
authors.forename: D
authors.initials: D
authors.lastname: Shonberg
mesh_terms: D000085:Acetates / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003118:Color Perception; D003124:Colorimetry; D004396:Coloring Agents / Q000737:chemistry; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008751:Methylene Blue / Q000737:chemistry; D018583:Pliability; D012995:Solubility; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry
chemical_list: D000085:Acetates; D000538:Aluminum Silicates; D004396:Coloring Agents; C075815:IPS-Empress ceramic; D016876:Metal Ceramic Alloys; C077451:Procera; D003776:Dental Porcelain; C070870:In-Ceram; D000431:Ethanol; D014025:Titanium; D000537:Aluminum Oxide; D008751:Methylene Blue