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Five Stages of Denture Base Resin

Denture base resins, or the bonding component that secures the artificial teeth to the base of the denture, have two components, liquid (monomer) and powder or (polymer). The polymer and monomer are mixed in a 3 to 1 ratio by volume which allows the powder to become the right consistency with minimal contraction or shrinkage. The length of each of the five stages that this mixture goes through is affected by room temperature.

  1. Sandy/Damp

    • The first stage of this polymer-monomer mass is called the sandy or damp stage. Here the concoction is cloudy, grainy and coarse with no change in its basic structure. Once the powder monomer and the liquid polymer are combined, the mixture gradually becomes a fluid.

    Tacky/Stringy

    • During the tacky stage, the watery mixture becomes stringy as the polymer chains unwind and the viscosity increases. The resin now adheres to any surface, and its stringy composition makes it easy to break.

    Dough

    • Next during the dough stage, sometimes called the gel stage, the mixture becomes a non-sticking pliable dough or putty that is the right consistency for packing. This is the process whereby the material is placed into the mold or flask, and this stage lasts generally from five to 10 minutes. Although the finished resin is not toxic, during this process the worker must wear gloves to avoid the monomer from entering the bloodstream through the skin.

    Elastic/Rubbery

    • As the monomer continues to evaporate, the mass becomes more elastic or rubbery. The rebounding property, when the mass is stretched and compressed, makes this stage unfit for molding.

    Solid/Stiff

    • The last stage of this resin is the tough or stiff stage. Here most of the monomer has evaporated and the material becomes a dry porous solid that resists any mechanical change. The stiff stage is reached during curing or polymerization. This process usually entails one of three heating methods. The slow method is simply a slow eight-hour or overnight water bath at 165 degree Fahrenheit; the rapid curing method involves dipping the denture into a 165-degree-Fahrenheit bath for two hours then raising the temperature to 212 degrees Fahrenheit for one hour. Over the last few years, as of 2010, microwave ovens are being used; however, the resin must be specially formulated and put into non-metallic flasks. Also, it is extremely important to remove any remaining monomer from the denture after polymerization because this can cause oral tissue irritation.

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