Abstract
During eating, the teeth usually endure the sharply temperature changes because of different foods. It is of importance to investigate the heat transfer and heat dissipation behavior of the dentino–enamel junction (DEJ) of human tooth since dentine and enamel have different thermophysical properties. The spatial and temporal temperature distributions on the enamel, dentine, and pulpal chamber of both the human tooth and its discontinuous boundaries, were measured using infrared thermography using a stepped temperature increase on the outer boundary of enamel crowns. The thermal diffusivities for enamel and dentine were deduced from the time dependent temperature change at the enamel and dentine layers. The thermal conductivities for enamel and dentine were calculated to be 0.81 Wm-1K-1 and 0.48 Wm-1K-1 respectively. The observed temperature discontinuities across the interfaces between enamel, dentine and pulp-chamber layers were due to the difference of thermal conductivities at interfaces rather than to the phase transformation. The temperature gradient distributes continuously across the enamel and dentine layers and their junction below a temperature of 42°C, whilst a negative thermal resistance is observed at interfaces above 42°C. These results suggest that the microstructure of the dentin-enamel junction (DEJ) junction play an important role in tooth heat transfer and protects the pulp from heat damage.
Highlights
Thermophysical properties of the human tooth, such as thermal diffusivity and conductivity impact heat transfer and are of great significance in the design of dental filling materials and equipment [1,2,3]
Six human mandible third molars from six different patients were used in the present study, a representative sample of sectioned tooth that included the dentino-enamel junction was used and calculations were based on a simplified model of heat transfer between the enamel surface and the underlying tissue
The shape of the dentino-enamel junction becomes clear and temperature levels increase from the right to the left; this is because the left portions of the patch heat up as energy is conducted away from the right patch
Summary
Thermophysical properties of the human tooth, such as thermal diffusivity and conductivity impact heat transfer and are of great significance in the design of dental filling materials and equipment [1,2,3]. These thermophysical properties are important in the pathophysiology of thermally induced pain and damage [4,5,6,7]. Knowledge about the heat diffusivity of different materials is potentially important for clinical decision making in PLOS ONE | DOI:10.1371/journal.pone.0158233. A simple yet reliable experimental measurement for determining thermophysical properties is needed
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