Mechanical and thermal response of enamel to IR radiation - a finite element mesoscopic model

Abstract

We present finite element models of human dental enamel that account for water-pores known to exist in this material, and use them to assess the influence of these pores on the temperature and stress profiles during and after single Er:YAG (2.9 µm) and CO2 (10.6 µm) laser pulses of duration 0.35 µs. Our results indicate that the temperature maximum is reached at the water-pores at the end of the laser pulse; this maximum seems to be independent of pore size for the CO2 laser but appears to be strongly dependent of pore size for the Er:YAG laser. The pressure reached at the water pore seems to be directly related to the temperature at the pore and it is significantly higher that the stress levels reached throughout the modelled structure, which indicates that water pores should play a significant role in the ablation mechanisms, even before water vaporization takes place. These results suggest that researchers conducting enamel ablation by Er:YAG lasers - or other lasers with wavelengths for which the absorption coefficients of the mineral and the water differ significantly - may want to select their samples and analyse their results taking into account factors that may alter the degree of mineralization of a tooth, such as age or type of tooth.