Trueness and precision of skin surface reproduction in digital workflows for facial prosthesis fabrication

Abstract

Statement of problemHow much skin surface details of facial prostheses can be transferred throughout the digital production chain has not been quantified. PurposeThe purpose of this in vitro study was to quantify the amount of skin surface details transferred from the prosthesis virtual design through the prototype printing with various additive manufacturing (AM) methods to the definitive silicone prosthesis with an indirect mold-making approach. Material and methodsTwelve test blocks with embossed wrinkles of 0.05 to 0.8 mm and 12 test blocks with applied earlobe skin structures were printed with stereolithography (SLA), direct light processing (DLP), and PolyJet methods (n=4). DLP and SLA prototype specimens were duplicated in wax. All specimens were then transferred into medical-grade silicone. Rz values of the wrinkle test blocks and the root mean square error (RMSE) of the earlobe test blocks were evaluated by laser topography to determine the trueness and precision of each stage. ResultsFor the earlobe test blocks, the PolyJet method had superior trueness and precision of the final skin surface reproduction. The SLA method showed the poorest trueness, and the DLP method, the lowest precision. For the wrinkle test blocks, the PolyJet method had the best wrinkle profile reproduction level, followed by DLP and SLA. ConclusionsThe indirect mold-making approach of facial prostheses manufacturing may be associated with 7% of skin surface profile loss with SLA, up to 20% with DLP, and no detail loss with PolyJet.