d. Characteristics of Completed Mixes. When a mix is ready for use, it should
be similar to the consistency of melted ice cream or liquid glue (adhesive rubber).
When the spatula is placed on the slab and the spatula is raised to one inch, the mix will
cling to the spatula in a thin thread (peak) for one or two seconds before it breaks and
then gradually spreads.
e. Precautions. The following precautions should be observed.
(1) Prevent loss or gain of moisture in liquid cement by keeping bottles
Dispense drops only when ready to mix.
Use a cool, dry glass slab (65 to 75 F).
Use the same brand of powder and liquid.
Add increments of powder slowly.
(6) Use the maximum amount of powder to obtain the desired consistency.
(To incorporate the most powder, the material should be mixed with a moderate circular
motion over a large area of the slab, turning the spatula often.)
1-15. CHARACTERISTICS OF POLYCARBOXYLATE CEMENT
a. General. The primary use of polycarboxylate cement is as a cementing
medium of cast alloy and porcelain restorations. In addition, it can be used as a cavity
liner, as a base under metallic restorations, or as a temporary restorative material.
b. Clinical Uses. Polycarboxylate cement is used in the same way as zinc
phosphate cement, both as an intermediate base and as a cementing medium.
(1) Powder. The composition of polycarboxylate cement powder may vary
slightly depending on manufacturers. It generally contains zinc oxide, 1 to 5 percent
magnesium oxide, and 10 to 40 percent aluminum oxide or other reinforcing fillers. A
small percentage of fluoride may be included.
(2) Liquid. Polycarboxylate cement liquid is approximately a 40 percent
aqueous solution of polyacrylic acid copolymer with other organic acids such as itaconic
acid. Due to its high molecular weight, the solution is rather thick (viscous).
d. Properties. The properties of polycarboxylate cement are identical to those
of zinc phosphate cement with one exception. Polycarboxylate cement has lower