title: In vitro human enamel wear by a hydrated high-alkali porcelain.
abstract: OBJECTIVE
  The purpose of this study was to examine the hydration of a high-alkali dental porcelain (Ducera LFC) and its relative abrasive wear against human enamel. The hypothesis is that the composition of the porcelain (LFC) will form a softer, hydrated layer in artificial saliva, which will reduce wear against enamel relative to other dental porcelains.
  
  
  METHODS
  The first experiment was to estimate the thickness of the hydrated layer formed on LFC by storage in artificial saliva using microindentation hardness. The second experiment involved an estimate of enamel wear relative to other porcelains (d-Sign, LFC, Ducera Gold, and the control substance, Ceramco II) of hydrated LFC using a pin-on-disk wear test.
  
  
  RESULTS
  The mean microindentation hardness values of hydrated and unhydrated LFC and the Ceramco II control were 5750 Mpa, 8230 Mpa, and 7180 MPa, respectively, at a stylus depth of 400 nm. The average enamel wear values measured with the porcelains are (in microns): LFC saliva (hydrated), 23.8; d-Sign, 35.6; LFC, 59.4; Ducera Gold (hydrated), 75; Ducera Gold, 81.3; Ceramco II, 109.4. Using Tukey's analysis at a 5% error level, there were significant differences between the wear of enamel against hydrated LFC and the more abrasive Ceramco II control.
  
  
  CONCLUSIONS
  Comparing the effect of hydration of LFC on enamel wear, using an independent t test, hydrated LFC was significantly less abrasive than LFC (P< .008), but was not significantly less abrasive than d-Sign.
authors.affiliation: School of Dentistry, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Hal P
authors.initials: HP
authors.lastname: O'Kray
authors.forename: William J
authors.initials: WJ
authors.lastname: O'Brien
mesh_terms: D003743:Dental Enamel / Q000737:chemistry*; D003776:Dental Porcelain / Q000009:adverse effects* / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008855:Microscopy, Electron, Scanning; D012464:Saliva, Artificial; D014072:Tooth Abrasion / Q000209:etiology / Q000517:prevention & control*
chemical_list: C095718:Duceram; D012464:Saliva, Artificial; D003776:Dental Porcelain