STUDY ON DENTAL TREATMENT WITH YAG LASER

用带光纤的双色高温计测量了脉冲YAG激光照射牙硬组织的冲洗温度。该高温计由硫族光纤和层压红外探测器组成。研究了激光功率对牙组织温度的影响，得到了激光功率与牙组织去除率的关系。为了检测对牙组织的热损伤，在不同温度下电加热后测量组织的硬度和弯曲强度。采用有限元热分析方法估计了牙体内的温度分布，讨论了热通量对牙髓的影响。所得结果如下：组织形貌在200℃左右开始发生变化，硬度随温度的升高而降低。其抗弯强度在50℃左右开始下降。由于组织与龋齿组织的能量吸收率差异较大，只能将龋齿组织从腔中取出。保护牙髓不受热损伤是可能的，因为牙齿组织的热导率很小，牙齿内的温度梯度非常陡峭。

The flush temperature of a dental hard tissue irradiated with pulsed YAG laser is measured using a two-color pyrometer with an optical fiber. This pyrometer consists of a chalcogenide optical fiber and a laminated infrared detector.The influence of the laser power on the temperature of the dental tissue is investigated, and the relation between the laser power and the removal volume of the dental tissue is obtained. In order to examine the thermal damage on the dental tissue, hardness and bending strength of the tissue are measured after being heated electrically at various temperature. FEM thermal analysis is conducted to estimate the temperature distribution in a teeth and to discuss the influence of heat flux on the dental pulp. The result obtained are as follows. The appcarance of the tissue begins to change at about 200℃ and its hardness decreases with the increase of temperature. Its bending strength starts to decrease at about 50℃. Only the carious tissue can be removed from the cavity due to the large difference of energy absorptivity between the tissue and the carious one. It is possible to protect the dental pulp from thermal damage, because the temperature gradient in the teeth is very steep due to the small thermal conductivity of the dental tissue.