Journal of Dental Research, Vol 66, 1040-1043, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Thermal diffusivity of glass-ionomer cements
W. M. Tay and M. Braden
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.
