Nd∶YAG激光辐照牙齿的光热作用理论研究

Theoretical investigation of opto-thermal transfer in human dentine irradiated by Nd∶YAG laser

激光辐照牙齿时所产生的温升容易引起牙髓细胞不可逆的损伤,导致牙髓细胞坏死,因此必须对相关的激光参数加以控制。建立了激光与牙齿相互作用的热传输模型,利用Crank-N icolson有限差分法数值模拟了不同Nd∶YAG激光参数照射下牙齿表面及内部的温度场的分布。计算结果表明,激光脉冲的宽度、间隔、个数决定了牙齿表面和牙髓腔壁的最终温度,将激光的总能量分配到几个脉冲之中,导致了牙齿表面温度的降低;而在牙髓腔壁出现了相反的情况,即脉冲数越多,牙齿内壁的温度也就越高。对相关的光热机理进行了探讨,提出控制单脉冲能量是光热蚀除牙齿应采用的最佳措施。

The major concern during laser irradiation of teeth is the high potential of tissue overheating resulting high temperatures that can spread in toward the dentin, causing irreversible damage to cells presented in the pulp chamber and leading to cell death,so the related laser irradiation parameters should be controlled strictly. The thermal diffusion model in dentin is built and the distribution of temperature field at the surface and subsurface region of dentin irradiated by Nd：YAG laser with different parameters is simulated numerically using Crank-Nicolson finite differential method. Calculation results show that the final temperature at the surface of dentin and at the pulp chamber wall depends on the pulse duration,interval and numbers. Laser irradiation by dividing total energy into several laser pulses leads to lower temperature at the dentin surface, while the reverse situation occurs at pulp region, the higher temperature is achieved with increasing pulse numbers. The related opto-thermal mechanism is discussed and it is put forward that controlling the energy of the single laser pulse is the optimum measure for optothermal ablation of dentin.