The three-dimensional casting distortion of five implant-supported frameworks.
The aim of this study was to assess three-dimensional distortion in cast full-arch, screw-retained titanium implant frameworks. A conventional commercial laboratory one-piece casting was used implementing the lost-wax technique. Five wax patterns were fabricated on a die-stone cast poured from a plaster impression of a five-implant brass analog. A reflex microscope was used to determine the three-dimensional casting error. Significant differences were found in distortion between wax patterns and castings, which, given the need to keep within 150 microm of misfit for passivity, were larger than the wax frameworks by between 416 and 477 microm. The greatest distortion occurred at the terminal implant abutments and in the vertical dimensions, but the distortion was inconsistent, indicating its three-dimensional nature. It is doubtful whether any conventionally cast titanium framework can be made to the degree of accuracy required to fit passively on its abutments because of the multiple variables inherent in this process.
Mitha
Tasneem
T
Department of Prosthodontics, School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Owen
C Peter
CP
Howes
Dale G
DG
D000044:Dental Abutments; D003722:Dental Alloys / Q000737:chemistry*; D003735:Dental Casting Technique; D015921:Dental Implants; D003761:Dental Impression Technique / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D019094:Dental Prosthesis, Implant-Supported; D003779:Denture Design; D003781:Denture Retention; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008853:Microscopy; D003765:Models, Dental; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
D003722:Dental Alloys; D015921:Dental Implants; D003764:Dental Materials; D014025:Titanium