Thermal stress distribution in laser-irradiated hard dental tissue: implications for dental applications

Abstract

This paper examines the thermomechanical effects of Er:YAG irradiation of tooth from a theoretical standpoint. Based on the high absorption coefficient of biological tissue at 2.94 micrometers , and the short interaction time between the photons at this wavelength and the tissue, effects of light scattering and heat conduction were neglected in calculating the temperature distributions in a tooth irradiated by Er:YAG laser. Radial and circumferential stresses developed as a result of temperature rise were then calculated on the surface of tooth. Radial stresses were always found to be compressive. Circumferential stresses, however, were compressive within a range inside the beam radius, and tensile outside the beam radius. Locations of the maximum tensile stress and maximum displacement were found to be outside and inside the beam radius, respectively. Maximum stresses and displacements decreased monotonically with increasing beam radius. Our results also revealed that ablation and thermal stresses beyond enamel strength could be reached within a single pulse.