title: Volumetric determination of the amount of misfit in CAD/CAM and cast implant frameworks: a multicenter laboratory study.
abstract: OBJECTIVE
  The purposes of this study were (1) to evaluate the fit between implant frameworks and implants fabricated with two types of implant framework fabrication techniques: computer-aided design/computer-assisted machining (CAD/CAM) and conventional casting with the lost wax technique; and (2) to describe a digital measurement system consisting of tactile scanning and computer software programs that measured the volumetric differences between implant-supported frameworks and implant restorative platforms fabricated with these technologies.
  
  
  METHODS
  This laboratory study used acrylic resin models with five interforaminal implants. The models were scanned; implant-level impressions and verification indexes were then made to construct master casts. First, a cast gold alloy framework and a titanium milled bar fabricated with CAD/CAM technology were made to clarify the construction processes of each. After this pilot study was completed, five cast and five CAD/CAM frameworks were made at each of three dental schools (15 milled and 15 cast bars). Each framework was made on a master cast from individual impressions. The implant restorative interfaces of the frameworks were scanned, and the data were entered into a computer software program. The virtual representations of the frameworks were fit onto digitized scans of the implant restorative platforms and used for virtual one-screw tests on both sides of the arch. Volumetric differences between the implant restorative platforms of the implant-supported frameworks and the model implants were measured to determine the amount of misfit between the frameworks and the model implants.
  
  
  RESULTS
  Implant-supported frameworks made with the CAD/CAM technology fit significantly better onto the implants than the cast implant frameworks. There was a significant difference between the right and left one-screw tests; there were no significant differences among the three university sites.
  
  
  CONCLUSIONS
  The CAD/CAM frameworks featured in this study were significantly more accurate than cast frameworks made with the lost-wax technique.
authors.affiliation: Department of Restorative and Prosthetic Dentistry, Ohio State University College of Dentistry, Ohio, USA. carl.drago@biomet.com
authors.forename: Carl
authors.initials: C
authors.lastname: Drago
authors.forename: Roxana L
authors.initials: RL
authors.lastname: Saldarriaga
authors.forename: Daniel
authors.initials: D
authors.lastname: Domagala
authors.forename: Riad
authors.initials: R
authors.lastname: Almasri
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D003735:Dental Casting Technique; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D006047:Gold Alloys; D003765:Models, Dental; D017755:Prosthesis Fitting; D014025:Titanium
chemical_list: D015921:Dental Implants; D006047:Gold Alloys; D014025:Titanium