title: Three-dimensional evaluation of gaps associated with fixed dental prostheses fabricated with new technologies.
abstract: BACKGROUND
  One of the most important factors in determining the clinical outcomes of fixed dental prostheses is the gap between the fixed dental prosthesis and the abutment. However, reports that investigated these gaps in the context of fixed dental prostheses fabricated with new technologies are few.
  
  
  OBJECTIVE
  The purpose of this study was to measure and analyze the fit of fixed dental prostheses. The fixed dental prostheses for the study were produced with the subtractive method (milling soft metal blocks), additive method (selective laser sintering), and traditional method (lost wax and casting).
  
  
  METHODS
  Ten specimens were fabricated with the soft metal block, selective laser sintering, and lost wax and casting methods. The 3-dimensional measurement method was adopted to obtain the measure gap figures of the specimens. To fabricate a digital replica, computer-aided design reference casts were prepared by scanning the study casts, and silicone replicas were fabricated for each specimen. These silicone replicas were scanned and obtained 40,000 point cloud data. The study also defined the mean gap for each specimen by averaging approximately 40,000 gap points to evaluate the fit of the specimens. Data were analyzed with 1-way ANOVA and the Tukey honestly significant difference (α=.05).
  
  
  RESULTS
  The mean gap was the smallest for fixed dental prostheses fabricated with the soft metal block, followed by the selective laser sintering, then the lost wax and casting. One-way ANOVA revealed statistically significant differences in the size of the gap among the 3 groups (P<.001), and the Tukey honestly significant difference test confirmed the specific differences among the groups (P<.05).
  
  
  CONCLUSIONS
  The fit obtained with the new soft metal block and selective laser sintering techniques was better than that obtained with the traditional lost wax and casting method. Thus, fixed dental prostheses produced by using these new techniques can be considered clinically acceptable.
authors.affiliation: Research Professor, Department of Dental Laboratory Science and Engineering, Korea University, Seoul, South Korea.
authors.forename: Ki-Baek
authors.initials: KB
authors.lastname: Kim
authors.affiliation: Doctoral student, Department of Dental Laboratory Science and Engineering, Korea University, Seoul, South Korea.
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Professor, Department of Dental Laboratory Science and Engineering, Korea University, Seoul, South Korea.
authors.forename: Woong-Chul
authors.initials: WC
authors.lastname: Kim
authors.affiliation: Professor, Department of Dental Laboratory Science and Engineering, Korea University, Seoul, South Korea. Electronic address: kjh2804@korea.ac.kr.
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kim
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry; D017076:Computer-Aided Design; D000044:Dental Abutments; D003735:Dental Casting Technique; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D003779:Denture Design; D003830:Denture, Partial, Fixed; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D003765:Models, Dental; D012828:Silicones / Q000737:chemistry; D013499:Surface Properties; D013674:Technology, Dental
chemical_list: D002858:Chromium Alloys; D003764:Dental Materials; D012828:Silicones