title: [The effects of firing numbers on the opening total pore volume, translucency parameter and color of dental all-ceramic systems].
abstract: OBJECTIVE
  To evaluate the effects of firing numbers on the total opening pore volume (TPV), translucency parameter (TP) and color of dental all-ceramic systems.
  
  
  METHODS
  Specimens of three kinds of all-ceramics systems were made, i.e. heat pressed all-ceramic (IPS Empress II), alumina all-ceramic (In-Cream alumina blanks) and zirconia all-ceramic (Cercon CAD/CAM zirconia). The specimens' TP, lightness (deltaL), chroma (deltaC) and TPV after 1, 3 and 5 firings were measured and calculated by spectrophotometer and surface area/porosity system. The data were analyzed statistically using SAS 8.0 software.
  
  
  RESULTS
  There were significant differences in TPV, TP, deltaL and deltaC for all-ceramic specimens at same number of firings (P<0.05), i.e. IPS>alumina and zirconia for TPV (P<0.05); IPS>zirconia>alumina for TP and deltaL (P<0.05); IPS and alumina>zirconia for deltaC (P<0.05). The significant differences also presented in TPV, TP, deltaL and deltaC for a same specimen at different number of firings (P<0.05). With increasing number of firings, TPV decreased, and TP, deltaL and deltaC increased gradually. There were negative linear correlation between number of firings and TPV, TP, deltaL and deltaC (P<0.05).
  
  
  CONCLUSIONS
  Repeated firings will affect TP and deltaL of all-ceramic restorations via the change of TPV.
authors.affiliation: Dept. of Prosthodontics, School of Stomatology of Fujian Medical University, Fuzhou 350002, China.
authors.forename: Shuigen
authors.initials: S
authors.lastname: Li
authors.forename: Liping
authors.initials: L
authors.lastname: Pang
authors.forename: Jiangwu
authors.initials: J
authors.lastname: Yao
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003116:Color; D017076:Computer-Aided Design; D003776:Dental Porcelain; D006801:Humans; D008027:Light; D008422:Materials Testing; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide