dental02.jpg (11342 bytes)Fundamentals of
Dental Materials

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Restorative Materials

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a. Equipment. The equipment required for mixing glass ionomer cement consists of a polymer paper pad or a glass mixing slab, a stainless steel spatula, and a matched set of powder and liquid.

b. Powder and Liquid. The normal ratio is one level scoop of powder to two drops of liquid. For cement bases, more powder may be added to the mix to achieve a thicker consistency. For accurate proportioning, shake the powder bottle to fluff the powder. Then, fill the scoop that comes with the bottle of powder without packing the powder down. When removing the scoop from the bottle, slide it against the plastic lip in the neck of the bottle to scrape off excess powder. Be sure to hold the bottle of liquid vertically when dispensing drops of liquid so as to produce precise and uniform drops. See figure 1-7.

c. Mixing. All powder is incorporated into the liquid in two or three large increments. Each portion of the powder should be added to the liquid all at once. To extend the working time, mix the powder and the liquid on a cold and dry glass slab. At room temperature, the mix should be completed in about one minute (60 seconds).

d. Characteristics of a Completed Mix. The right consistency is obtained when the material breaks away from the spatula when it is raised one-half inch from the glass slab.

Figure 1-7. Dispensing uniform drops of glass ionomer liquid.

e. Precautions. The following precautions should be observed.

(1) Do not insert glass ionomer cement as a ball of material into deep cavities or where the dentin is thin or where there is danger of pulpal involvement. In these cases, set in place a calcium hydroxide liner before inserting the glass ionomer cement.

(2) There may be an allergic reaction to the glass ionomer cement, in some cases.

(3) Upon contact with eyes, the powder may cause irritation due to foreign body reaction. Similarly, ingestion of the liquid may cause local irritation.

(4) All enamel, dentin, and metal surfaces must be clean and dry before use of glass ionomer cement.

(5) Do not overfill the crown. Brush a thin coat of glass ionomer cement on the internal crown surface and abutments.

(6) Bottles of liquid or powder should be tightly closed after use to prevent moisture contamination of the powder and evaporation of the liquid.

David L. Heiserman, Editor

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Revised: May 22, 2017