dental02.jpg (11342 bytes)Fundamentals of
Dental Materials

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Dental Resins, Miscellaneous Dental Materials, and Dental Gold/Alloys

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2-2. ACRYLIC RESINS

a. Clinical Use. Acrylic (unfilled) resins are used as temporary crown material. Temporary crowns are placed to protect the crown preparation and provide patient comfort during the time the permanent crown is being constructed.

b. Composition of Acrylic Resins.

(1) Powder. The powder is composed of a polymethyl methacrylate, a polymer, and contains some inert coloring pigments.

(2) Liquid. The liquid is a monomethyl methacrylate, a monomer, and is the same material as the polymer except in a different molecular form.

c. Properties of Acrylic Resins.

(1) Desirable properties. Acrylic resins are available in several shades to match tooth shading (esthetics). They have a low thermal conductivity. These resins are not easily washed out by the acids of the oral cavity (low solubility). Acrylic resins are also resilient, which allows them to be used in stress-bearing areas.

(2) Undesirable properties. Acrylic resins exhibit a moderate shrinkage of from 3 to 8 percent. This shrinkage and low marginal strength can lead to marginal leakage. Acrylic resins have a low resistance to wear. Acrylic resins cannot be used over a zinc oxide and eugenol-type base because eugenol interferes with the acrylic curing process.

d. Mixing. Always follow the manufacturer's directions when mixing any material. Each brand of acrylic resin requires a slightly different mixing procedure. Insufficient mixing will cause an uneven color or streaks in the mixture. Overmixing will cause the material to harden before it can be placed.

David L. Heiserman, Editor

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Revised: May 22, 2017