Thermal Diffusivity of Glass-ionomer Cements

Abstract

Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1 degree C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of P/L, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogenous isotropic materials.

Heat transfer properties and thermal cure of glass-ionomer dental cements

“…These effects relate to the thermal properties of the glass powders in these cements, and showed that increases in the powder:liquid ratio reduce the temperature rise for a given input of heat, but increases the rate at which heat spreads through the material. These effects, particularly for thermal diffusivity, have been confirmed by other workers [12][13][14].…”

“…An early study considered the property of thermal diffusivity, i.e. the measure of how quickly a material reacts to a change in temperature [14] and showed it to be low for some of the earliest commercial brands of glass-ionomer cement. This study also reported that glass-ionomers were good thermal insulators [14], a finding that has been confirmed in other studies concerned mainly with thermal diffusivity [12,13,23].…”

Effects of Time Delay on Degree of Conversion of Contemporary Orthodontic Band Adhesives

“…12 If an optimum degree of cure cannot be achieved for band adhesives, it might cause an increase in water sorption, decrease in hardness, and softening of the polymer matrix. 13 In addition, monomer conversion of resin composites at 72-and 120-hour delays provided higher values than the 5-minute-delay composite group.…”

Studies on electrical and thermal properties of dental glass ionomer cement

“…But so far no report has been found for the temperature dependent ionic conduc-tivity of these materials in the solid state. The measurement of dielectric constant and resistivity of these materials has been used to monitor their setting characteristics [8,9].…”