Properties of Natural Waxes Used in Dentistry

¹ University of Michigan, School of Dentistry, Ann Arbor, Michigan

The purpose of this investigation was to categorize the ingredient waxes used in dental waxes by means of physical tests. Five mineral, four plant, two insect, and two inlay waxes were included. Their melting range, setting range, as determined from a plot of temperature change versus time, flow properties, and linear thermal expansion between 22° and 52° C. were studied.

The melting range, measured by the closed-capillary-tube method, and the setting range of the waxes were in fair agreement. Most of the waxes investigated solidified in a range of 2° to 3° C. between temperatures of 41° and 87° C. Each of the two inlay waxes exhibited two setting ranges. The rate of temperature change during solidification was much greater for paraffin than for beeswax. Japan wax was the only wax investigated that exhibited supercooling during solidification.

The mineral, insect, and inlay waxes flowed extensively at approximately 20° C. below their setting ranges. The mineral waxes required about a 10° C. temperature rise between 1 and 70 per cent flow. The plant waxes did not flow until they reached a temperature of 5° C. or less than their setting range. The temperature rise between 1 and 70 per cent flow for the plant waxes was 2.6° to 8.0° C.

The coefficients of linear thermal expansion were less for plant waxes than for mineral waxes. Carnauba possessed the smallest coefficient of linear thermal expansion— 156 ± 10 x 10^–6/° C.—of all the waxes and was the only wax which exhibited a linear expansion between 22° and 52° C. All the other waxes had at least two rates of expansion over this temperature range.