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|Type:||Artigo de periódico|
|Title:||Over-refractory casting technique as an alternative to one-piece multi-unit fixed partial denture frameworks|
|Abstract:||Statement of problem. Soldering has been suggested to achieve acceptable fit of multi-unit fixed partial denture (FPD) frameworks of 3 or more elements. However, distortion of the entire framework may occur. Purpose. The purpose of this study was to evaluate marginal fit in 1-piece-casting FPD frameworks comparing 2 casting techniques: the conventional technique (CT) and the over-refractory, technique (ORT). The techniques were evaluated on castings made from commercially pure titanium (CP Ti; Tritan), titanium-aluminum-vanadium (Ti-6AI-4V), and nickel-chromium (Ni-Cr; VeraBond II) alloys. Material and methods. A metal master cast including 3 preparations was created to simulate a 5-unit FPD. The metal cast was duplicated in vinyl polysiloxane for fabrication of 60 working casts. For the CT, 0.7-mm-thick patterns were waxed on the casts using an electrical wax-clipping unit. Patterns were removed from the preparations before investing. For the ORT, the silicone impressions were poured with an investment material (Rematitan for CP Ti and Ti-6Al-4V, and Talladium for Ni-Cr). The patterns were waxed on the refractory casts, and the assembly, was invested. Both CT and ORT (n=10), CP Ti, and Ti-6Al-4V frameworks were cast using an arc-melting titanium vacuum-casting machine. The Ni-Cr frameworks were cast using an automated centrifugal-casting machine. The mean marginal discrepancies of the frameworks were measured at the mesial, distal, buccal, and lingual interfaces. Marginal gap measurements were recorded 3 times for each surface to the nearest 0.5 mu m using a traveling microscope (X50). The data were analyzed with 2-way analysis of variance, followed by the Tukey HSD test (alpha=.05). Results. Marginal discrepancies for the ORT specimens (82.8 +/- 1.7 mu m for CP Ti; 64.4 +/- 1.3 mu m for Ti-6Al-4V; and 77.2 +/- 1.5 mu m-for Ni-Cr) were significantly lower than those obtained for the CT specimens (106.3 +/- 2.6 mu m for CP Ti; 75.7 +/- 0.8 mu m for Ti-6Al-4V; 101.9 +/- 1.7 mu m for Ni-Cr) (P <.05). For both techniques, marginal discrepancies were significantly different among the alloys evaluated, presenting the following order firorn greatest to least marginal discrepancy: CP Ti, Ni-Cr alloy, and Ti-6AI-4V (P <.05). Conclusion. The ORT for multi-unit FPD frameworks demonstrated significantly lower marginal discrepancies than the CT.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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