Fresagem de polipropileno para confecção de guia cirúrgico e sua resistência a esterilização em autoclave: um estudo in vitro

Abstract

The present work refers to a research of applicability of Polypropylene copolymer (CoPP), performing in vitro tests in order to evaluate the fidelity of the material for the preparation of surgical guides (GC) planned and produced by CAD / CAM technology ( Computer Aided Design / Computer Aided Manufacturing) for guided dental implant surgery. From the scanning with extra-oral scanner of a resin dummy, a file with extension STL (stereolithography) was generated, starting from this image a GC was drawn on it by the software Blue Sky Plan 4® and Meshmixer®. With the finalized GC planned, a properly sized Polypropylene (CoPP) plate was placed in position on the 5-axis dental milling machine for four GC milling. After machining they were divided into pairs and underwent sterilization process in two separate cycles in wet steam autoclave under high temperatures. Each of the GC's was re-scanned after milling and sterilization, and then subjected to statistical analysis using CloudCompare® v 2.7 software, in which the post milling and sterilization images were compared to the digital planning guide image, giving the possibility of observe how faithful CoPP GCs were when machined. In addition to analyzing the degree of distortion when undergoing the sterilization process. In the results we observed larger errors in the scanning and milling processes compared to the sterilization process of the guides. Although these were minimal errors, scanning can be improved technique and milling strategy can be adjusted according to CoPP properties. In the visual analysis of colorimetry, the green tones predominated in the samples, both after milling and post sterilization, resulting in a surgical guide with high precision value and little variance. We believe it is relevant to continue the studies regarding Polypropylene, milling and sterilization with larger samples, and perform in vitro dental implant surgery to analyze the degree of screw deviation when using a Polypropylene guide (sic).