title: [Effects of repeated firing on microleakage of selective laser melting ceramic crowns].
abstract: OBJECTIVE
  To investigate the effects of repeated firing on microleakage of selective laser melting ceramic crowns.
  
  
  METHODS
  Fifty molars were randomly divided into 2 groups (25 teeth in each group). Teeth in group A received a chamfer finish line preparation, whereas teeth in group B received a shoulder finish line. After SLM metal crowns were fabricated, all the crowns received initial oxidation step, opaque firing, dentin firing and glaze firing, then crowns in each group were randomly divided into 5 sub-groups according to different time of clinical firings. Glass ionomer was applied for bonding. After 5000 thermocycles ranging from 5degrees centigrade to 55degrees centigrade, all the specimens was evaluated by dye penetration and then microleakage was examined under light microscopy. The data were analyzed with SPSS 20.0 software package.
  
  
  RESULTS
  Microleakage between all specimens of group A were not statistically significant (P>0.05) whereas that of group B were statistically significant (P<0.05); After the fifth time of clinical firing, microleakage of specimens in group B(B5) were significantly higher than that of group A(A5).
  
  
  CONCLUSIONS
  Repeated firings had no significant influence on marginal microleakage of SLM ceramic crowns whereas the crowns of chamfer finish lines result in better clinical performance after repeated firings.
authors.affiliation: Shanghai Stomatological Hospital. Shanghai 200031, China. E-mail:zhongqun681115@qq.com.
authors.forename: Qun
authors.initials: Q
authors.lastname: Zhong
authors.forename: Yan
authors.initials: Y
authors.lastname: Peng
authors.forename: Xue-Ying
authors.initials: XY
authors.lastname: Wu
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Weng
mesh_terms: D003442:Crowns; D003763:Dental Leakage; D003776:Dental Porcelain; D003804:Dentin; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D019279:Resin Cements; D013499:Surface Properties
chemical_list: D019279:Resin Cements; D003776:Dental Porcelain