title: Marginal and internal fits of fixed dental prostheses zirconia retainers.
abstract: OBJECTIVE
  CAM (computer-aided manufacturing) and CAD (computer-aided design)/CAM systems facilitate the use of zirconia substructure materials for all-ceramic fixed partial dentures. This in vitro study compared the precision of fit of frameworks milled from semi-sintered zirconia blocks that were designed and machined with two CAD/CAM and one CAM system.
  
  
  METHODS
  Three-unit posterior fixed dental prostheses (FDP) (n=10) were fabricated for standardized dies by: a milling center CAD/CAM system (Etkon), a laboratory CAD/CAM system (Cerec InLab), and a laboratory CAM system (Cercon). After adaptation by a dental technician, the FDP were cemented on definitive dies, embedded and sectioned. The marginal and internal fits were measured under an optical microscope at 50x magnification. A one-way analysis of variance (ANOVA) was used to compare data (alpha=0.05).
  
  
  RESULTS
  The mean (S.D.) for the marginal fit and internal fit adaptation were: 29.1 microm (14.0) and 62.7 microm (18.9) for the milling center system, 56.6 microm (19.6) and 73.5 microm (20.6) for the laboratory CAD/CAM system, and 81.4 microm (20.3) and 119.2 microm (37.5) for the laboratory CAM system. One-way ANOVA showed significant differences between systems for marginal fit (P<0.001) and internal fit (P<0.001).
  
  
  CONCLUSIONS
  All systems showed marginal gaps below 120 microm and were therefore considered clinically acceptable. The CAD/CAM systems were more precise than the CAM system.
authors.affiliation: Department of Prosthodontics, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Beuer
authors.forename: Hans
authors.initials: H
authors.lastname: Aggstaller
authors.forename: Daniel
authors.initials: D
authors.lastname: Edelhoff
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gernet
authors.forename: John
authors.initials: J
authors.lastname: Sorensen
mesh_terms: D001641:Bicuspid; D017076:Computer-Aided Design / Q000295:instrumentation; D000044:Dental Abutments; D003738:Dental Cements / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation*; D003830:Denture, Partial, Fixed; D006801:Humans; D007754:Laboratories, Dental; D008422:Materials Testing; D008963:Molar; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003738:Dental Cements; D003764:Dental Materials; D015040:Zirconium; C028541:zirconium oxide