Antibacterial properties of a self-cured acrylic resin composed of a polymer coated with a silver-containing organic composite antibacterial agent.

A novel antibacterial polymer, coated with a silver-containing organic composite antibacterial agent, was dispersed in a self-cured acrylic resin. Residual viable cell count of each oral bacterial and fungal species cultivated on acrylic resin specimens containing the antibacterial polymer was significantly decreased when compared to those cultivated on specimens prepared from untreated polymer. A strong inverse correlation was found between the amount of eluted silver ions and the residual viable cell count of all species grown on the antibacterial polymer: the lower the viable cell count, the higher the amount of eluted silver ions. This clearly indicated the antibacterial activity of silver ions. As the content of organic composite antibacterial agent added to the polymer increased from 0.5% to 1.5% in 0.5% increments, amount of eluted silver ions significantly increased with each 0.5% increment to exert greater antibacterial effect.

The effect of zinc levels in a gold-based alloy on porcelain-metal bonding.

OBJECTIVES: The purpose of this study was to ascertain whether the amount of Zn in gold alloys contributes to porcelain-metal bonding. METHODS: Experiments were carried out using a commercial Pd-free gold alloy with a nominal composition of 88.7 wt% Au, 9.49 wt% Pt, 1.5 wt% Zn, 0.1 wt% Mn, 0.2 wt% Rh, and 0.1 wt% Ir, which contains Zn and no other elements (In, Sn, Fe) known to affect porcelain-metal bond strength. To establish the effect of oxidation of the metal surface, porcelain was applied both to preoxidized and to non-preoxidized metal specimens. The bond strength was evaluated by means of the ISO 9693: 1999 crack initiation test. A conventional gold alloy was used as a control. The elemental distributions at the porcelain/alloy interfaces were analyzed in cross section by electron probe microanalysis. Additionally, after the bond strength test, cross-sections of the interfaces of the debonded specimens were microscopically analyzed to characterize the fracture mode. RESULTS: The Pd-free gold alloy joints showed significantly higher bond strength values than joints made with conventional gold alloy. Preoxidation treatment significantly increases the bond strength, in the preoxidized joints Zn was highly localized at the interface and diffused into the porcelain up to about 10 µm from the interface, and the joint failed by cohesive fracture in the porcelain. In contrast, the non-preoxidized joint showed mainly adhesive fracture at the porcelain/alloy interface. SIGNIFICANCE: The presence of Zn in gold alloys plays a part in establishing chemical bonding thus improving the bond strength between porcelain and alloy.

Effect of self-cured acrylic resin added with an inorganic antibacterial agent on Streptococcus mutans.

In order to develop an self-cured acrylic resin having an antibacterial property, three types of commercially available inorganic antibacterial agents were added, at 1% each, to UNIFAST III to evaluate the antibacterial property. The antibacterial test evaluated the amount of Streptococcus mutans attached to UNIFAST III, the residual viable count of Streptococcus mutans cultured on UNIFAST III. And the color tone changes evaluated immediate and temporal color tone changes of UNIFAST III caused by the addition of antibacterial agents. As a result, compared to UNIFAST III without any added inorganic antibacterial agent, a significant decrease was observed in the attachment amount and the residual viable count of Streptococcus mutans. In addition, when adding NOVARON from among the added inorganic antibacterial agents, UNIFAST III exhibited little change in the temporal color tone. Thus, these results suggest that the addition of antibacterial agents to resins is effective first step toward developing self-cured acrylic resins having an antibacterial property.