MODELING PHOTOTHERMAL HEATING ANDABLATION OF BIOLOGICAL HARD TISSUES BYSHORT AND ULTRASHORT LASER PULSES

摘要

Successful implementation of lasers into soft-tissue surgery has fueled interest in the implementation of similar hard-tissue applications in laser dentistry and laser medicine. However, unlike most soft tissues, which are composed mostly of water and some organic matter, hard tissues contain a large mineral component which affects the tissue's optical and thermal properties. This can make soft-tissue lasers unsuitable for hard-tissue applications depending on the laser wavelength. Additionally, hard tis-sues are more susceptible to thermal injury than soft tissues, and therefore special care must be given to ensure minimal thermal accumulation in surrounding tissues. Short and ultrashort laser pulses hold key interest as they can allow for deposition of thermal energy to the target area by many orders of magnitude faster than the heat diffusion process that leaks heat to adjacent cells. For these reasons, time-dependent thermal simulations are performed for short and ultrashort single pulse laser-tissue interac-tions, as well as a simulation for a multipulse heating mode that utilizes the repetition of ultrashort pulses. A comparative analysis for both radiation modes is discussed, with special attention given to minimization of thermal accumulation, as that is the main factor determining cell death and tissue regrowth rates. Using these recommen-dations should help to optimize patient recovery times when applied to laser surgery and laser dentistry.