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The effect of triphenylbismuth on the radiopacity and performance properties of compression- and injection-molded denture resins.

PURPOSE
Methods of incorporating radiopaque triphenylbismuth into an experimental compression-molded and injection-molded heat-polymerized resins were determined. The transverse flexural properties, radiopacity, and color stability of the resins containing triphenylbismuth were then compared with a commercially available, compression-molded denture resin.


MATERIALS AND METHODS
Varying levels of triphenylbismuth were added to both the monomer and polymer in heat-polymerized denture resin systems to determine the level of the additive that was necessary to achieve a radiopacity similar to 0.2 mm of copper with minimum resin porosity. Specimens were then prepared by incorporating 0% or 30% wt/wt triphenylbismuth into resins. The commercially available polymethyl methacrylate resin served as a benchmark for physical property comparison, and no additive was included during its polymerization. At 30% wt/wt triphenylbismuth, resin color stability, transverse deflection, and radiopacity were evaluated using methods described in International Standards Organization Standard 4049 and American Dental Association Specification No. 12. The transverse deflection results among the resin groups were compared with a reference resin using the Kruskal-Wallis method (alpha = 0.05).


RESULTS
Incorporation of triphenylbismuth into the monomer of the injection material, resulting in 30% wt/wt in the polymerized resin, produced a level of radiopacity similar to 0.2 mm copper. Although the injection-molded resin with 30% wt/wt triphenylbismuth remained translucent, the compression-molded resin was opaque, indicating excessive air-entrapment porosity. The additive caused a faint yellowing in both types of resins, but color stability was not affected. Transverse deflection of the injection-molded resin (4.5 +/- 0.5 mm) and the injection-molded resin with triphenylbismuth (3.8 +/- 1.7 mm) was greater than that of the experimental resin (3.5 +/- 0.2 mm), which was equal to the commercial resin (3.6 +/- 0.2 mm). Triphenylbismuth at 30% wt/wt significantly reduced transverse deflection for the experimental resin (2.6 +/- 0.5 mm).


CONCLUSIONS
Triphenylbismuth at a final concentration of 30% wt/wt can be added to polymethyl methacrylate injection-molded resins to provide a high level of detection on chest or abdominal radiographs without adversely affecting resin color stability and transverse deflection.