PubMed · 4932374
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C M McEachern. 1971. Plastic transfer copings.. https://pubmed.ncbi.nlm.nih.gov/4932374/
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STATEMENT OF PROBLEM: Although internal porosity is a potential risk factor for clasp fracture, little is known about its frequency in the clasps of titanium removable partial dentures. PURPOSE: This study investigated the influence of the direction of auxiliary sprues on porosity in the circumferential clasps of a pressure-cast titanium removable partial denture. MATERIAL AND METHODS: Wax patterns of a removable partial denture framework were made on 10 identical refractory casts of a Kennedy class II, modification 1, mandibular partially edentulous arch. For the auxiliary sprues directed to the circumferential clasps, 2 designs were used: straight and curved. Casting was performed in a 1-chamber pressure casting machine. Pore number and size were assessed on radiographs of the castings. The data were analyzed with the 2-tailed Student t test (P <.05). Randomly selected specimens were sectioned for morphologic observation of the internal surface of the pores. RESULTS: The number of pores >or=0.5 mm diameter and the total number of pores were significantly lower in the molar lingual arms of the curved sprue group than in the corresponding clasp arms of the straight sprue group (P =.03 and P =.009, respectively). No significant differences between the 2 groups were found for pores of any size in other locations. The pores had smooth internal surfaces. CONCLUSION: Within the limitations of this study, the curved sprue design produced significantly less porosity in the circumferential clasp arms of a cast titanium removable partial denture than the conventional straight design. The results suggest that internal porosity in titanium castings can be controlled through sprue design.
This article presents a technique for the fabrication and incorporation of a stable and fireproof identification plate into a cast partial denture framework. Embossing tape is embedded in the wax pattern of the major connector. The resulting casting reproduces the embossed lettering, which is identifiable through the tissue-colored acrylic denture base resin.
Patients who cannot tolerate total coverage of the hard palate or whose maxillary arches are poorly formed, because of congenital, developmental or surgical defects, may be unable to wear a conventional complete denture. These patients can be successfully treated with implant-supported prostheses that cover only a minimal amount of palatal tissue. With spark-eroded castings, very precise restorations can be constructed to fit such implant supports. However, these castings are so expensive that cost precludes their use for many patients. This article presents an alternative approach, developed with the refined techniques used for removable partial dentures, which can yield results similar to those for spark-eroded castings at a fraction of the cost. The clinical and laboratory procedures involved in this technique are described.