title: Investigation of the fracture resistance of three types of zirconia posts in all-ceramic post-and-core restorations.
abstract: OBJECTIVE
  All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal cores. In certain clinical cases, however, fractures at the junction between the post and the core have been reported. The objective is therefore to improve the strength between the post and the core.
  
  
  METHODS
  Three different methods were used to fabricate all-ceramic post-and-core restorations: pressing IPS Empress cores directly to CosmoPost zirconia posts, adhesively luting IPS Empress cores to CosmoPost zirconia posts, and Celay milling In-Ceram zirconia blanks to one-piece post-and-core restorations. Ten restorations were prepared with each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded.
  
  
  RESULTS
  The highest breaking load and highest deflection were recorded for the luting technique, with values of 25.3 N and 394 microns, respectively. The corresponding values for the pressed cores and the milled zirconia cores were 22 N and 301 microns, and 13 N and 160 microns. All differences were statistically significant at P < .05. Regarding the load dependence of the deflection, the luted cores again demonstrated the highest mean value, with 15.5 microns/N, while this value was 13.6 microns/N and 13 microns/N for the pressed-on and milled cores, respectively. These differences were not statistically significant.
  
  
  CONCLUSIONS
  Adhesively luted all-ceramic cores on zirconia posts offer a viable alternative to the conventional pressed technique.
authors.affiliation: Department of Prosthodontics, School of Dentistry, University of Chosun, Kwang-Ju, Korea.
authors.forename: Seung-Mi
authors.initials: SM
authors.lastname: Jeong
authors.forename: Klaus
authors.initials: K
authors.lastname: Ludwig
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D000537:Aluminum Oxide; D000538:Aluminum Silicates; D000704:Analysis of Variance; D002484:Cementation; D002516:Ceramics; D003722:Dental Alloys; D003775:Dental Polishing; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D008422:Materials Testing; D011176:Post and Core Technique; D015040:Zirconium
chemical_list: D000538:Aluminum Silicates; D003722:Dental Alloys; C075815:IPS-Empress ceramic; D003776:Dental Porcelain; C070870:In-Ceram; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide