A STUDY ON DIAGNOSITIC METHODES OF DENTAL PULP BY PULSE OXIMETRY IN YOUNG PERMANENT TEETH AND DECIDUOUS TEETH

在这项研究中，我们成功地记录了年轻人牙髓的透射光体积脉搏波（TLP），并检验了它在牙髓活力测试中的适用性。本研究使用1名成人和6名儿童的上中切牙。在受试者的上牙弓石膏模型上制备被检查牙齿的树脂帽。绿色发光二极管（LED，峰值功率为525nm）通过连接在单个树脂帽上的光纤照射被检查牙齿的腭面，通过牙髓的透射光从牙齿的唇面被采集。透射光的强度被引导到CdS光导电池（峰值灵敏度为550nm），并通过交流耦合放大器记录其强度变化作为TLP，同时记录受试者手指体积描记图。录音是在暗室中使用和不使用不透明的黑色橡胶坝进行的。在1例患者中，将含有1/80,000肾上腺素的2%利多卡因溶液浸润根尖周围，观察TLP振幅的变化。结果表明：1)在成人和青少年的正常恒牙中均可识别出与手指体积脉搏波同步的张力点。年轻被试的TLP信号幅值更大，波形更清晰。2)脱位牙对牙髓电刺激无反应，有轻微的TLP记录。但对于植牙，没有检测到明显的脉搏波。3)大坝应用没有产生显著的信号降低。4) 2%LE在根尖周浸润后，TLP的振幅先减小后增大。结果表明，TLP可以反映牙髓血流动力学，该系统可用于年轻恒牙牙髓活力的诊断，而不会引起任何疼痛感。

In this study, we succeeded to record transmitted-light photoplethysmography (TLP) from the dental pulp in young humans and examined its applicability to pulp vitality test. Upper central incisors of one adult and six children were used for this investigation. A resin cap of the examined tooth was prepared on the plaster model of the subjects' upper arch. A green light-emitting diode( LED, peak power at 525nm) illuminated the palatal surface of the examined tooth via an optical fiber attached to the individual resin cap, and the transmitted-light through the pulp was picked up from the labial surface of the tooth. The intensity of the transmitted-light was guided to a CdS photoconductive cell (peak sensitivity at 550nm), and its intensity change was recorded as TLP through AC-coupled amplifier together with the finger plethysmography of the subjects. Recordings were made with and without opaque black rubber dam application in a dark room. In one subject, 2% lidocaine solution containing 1/80,000 epinephrine was periapically infiltrated and the transition of the amplitude of the TLP was observed. Results obtained were as follows : 1) TLP, synchronous with the finger plethysmography, was recognized from sound permanent teeth of an adult and the young subjects. The signal amplitude of the TLP was larger and the waveform was much more clearer with the young subjects. 2) TLP was slightly recorded from luxated teeth which did not respond to electrical stimulation to the pulp. But with an implanted tooth no obvious pulse wave was detected. 3) The dam application did not produce a significant signal reduction. 4) Periapical infiltration of 2%LE produced a gradual decrease of the amplitude of TLP and then was followed by an increase. Results indicated that TLP is considered to reflect pulpal haemodynamics and this system would be useful for the diagnosis of pulpal vitality of the young permanent teeth without eliciting any pain sensation.