PubMed · 4557300
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W Finger, P Lockowandt. 1972. [Impression and model materials, a functional unit].. https://pubmed.ncbi.nlm.nih.gov/4557300/
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OBJECTIVES: This paper describes a method of making titanium dental crowns by means of integrating laser measuring, numerical simulation and rapid prototype (RP) manufacture of wax patterns for the investment casting process. METHODS: Four real tooth crowns (FDI No. 24, 25, 26, 27) were measured by means of 3D laser scanning. The laser digitized geometry of the crowns was processed and converted into standard CAD models in STL format, which is used by RP systems and numerical simulation software. Commercial software (MAGMASOFT) was used to simulate the casting process and optimize the runner and gating system (sprue) design. RP crowns were 'printed' directly on a ModelMaker II 3D Plotting System. A silicone negative mold (soft tool) was made from the RP crowns, then more than hundreds wax crowns were duplicated. The duplicated crowns were joined to the optimized runner and gating system. By using the investment casting process 20-25 replicas of each crown were made on a centrifugal casting machine. All castings were examined for porosity by X-ray radiographs. RESULTS: By using the integrated scanning, simulation, RP pattern and casting procedure, cast crowns, free of porosity, with excellent functional contour and a smooth surface finish, were obtained from the first casting trial. SIGNIFICANCE: The coupling of laser digitizing and RP indicates a potential to replace the traditional 'impression taking and waxing' procedure in dental laboratory, with the quality of the cast titanium prostheses also being improved by using the numerically optimized runner and gating system design.
Modifying a Super-Sep bottle by adding a brush to the lid for paint-on use allows for the precise application of the separating medium used when flasking dentures. Super-Sep offers many advantages over other commonly used separating mediums: It is virtually dimensionless, allowing for better accuracy; it dries quickly and functions best on moist stone; and it can be poured against immediately. The latter fact means less time is needed before the subsequent layers of stone can be applied when denture flasking.
It is not possible for the wax pattern of most large-volume maxillary resection obturators to be placed into a flask for conventional compression molding processing and positioning of the wax pattern. However, these wax patterns and their channel access design often can be modified and aligned in position for processing with the continuous pressure injection technique. This article describes the use of the continuous pressure injection technique to process the perpendicularly aligned wax pattern of a maxillary resection obturator. It also describes a modified channel design and a simple method to pull back the injection funnel to increase the volume of the flask.