Measurement of thermophysical properties of human dentin: effect of open porosity.
In dentistry caries removal can be performed with rotatory instruments or high intensity laser. Both techniques can heat the tooth and harm the pulp. The literature review about the measurement of human dentin thermophysical properties revealed a great variation of the values obtained by several authors, and most of the studies are outdated. Most of these studies have not directly measured the thermal diffusivity of human dentin, and the reported values are calculated values based on measurements of conductivity, density and specific heat.


OBJECTIVE
The aim of the present study was to measure human dentin thermal diffusivity, density, open porosity and specific heat, and then to calculate its thermal conductivity and analyze the influence of open porosity in these properties.


METHODS
The methods used were: flash laser method for measuring thermal diffusivity, method of penetration and immersion with xylol for density and open porosity and differential scanning calorimetry for measuring specific heat. Calculated results of the thermal conductivity are shown as well.


RESULTS
Results of diffusivity, density, open porosity, specific heat and thermal conductivity of measurements performed on five samples are presented and compared with results of other authors. The open porosity of the samples varied between 1.11% and 3.08% of the sample volume, corresponding to densities ranging between 2090 and 2400 kg m(-3), thermal diffusivity: 0.199 and 0.265 x 10(-6)m2 s(-1), specific heat: 872.5 and 1181.0 J kg(-1)K(-1), thermal conductivity: 0.363 and 0.666 W m(-1)K(-1).


CONCLUSIONS
It has been found that there exist a strong correlation between the open porosity of human dentin and its thermal conductivity and density. Both human dentin thermal conductivity and density decrease with the increasing of open porosity, with a confidence of at least 98% and 96.6%, respectively.
Departamento de Engenharia Mecânica, Universidade Federal de Minas Gerais, Avenida Presidente Antônio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais, Brazil. manoelita@uai.com.br
Manoelita
M
Figueiredo de Magalhães
Ricardo Alberto
RA
Neto Ferreira
Pablo Andrade
PA
Grossi
Roberto Márcio
RM
de Andrade
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D002152:Calorimetry, Differential Scanning; D003804:Dentin / Q000502:physiology* / Q000648:ultrastructure; D004058:Diffusion; D006358:Hot Temperature; D006801:Humans; D007101:Immersion; D007834:Lasers; D008422:Materials Testing; D008954:Models, Biological; D016062:Porosity; D013814:Thermal Conductivity