Application of transmitted laser light for the assessment of human pulp vitality

这项研究的目的是确定使用透射式激光是否可以比使用背向散射光(LDF：激光多普勒血流仪)更好地评估人类牙髓的活力。实验在6名年龄23-28岁的受试者的10颗上颌中切牙上进行，其中5颗牙齿是活的，没有修复，5颗是不活的。为了与透射式激光一起使用，使用了传统LDF仪器探头内的光纤，一种用于将光传输到颊表面，另一种用于在同一牙齿的腭面接收光。对于LDF，探头固定在颊表面。测量每颗实验牙的三个不同位置的血流量(BF)：牙冠的切1/3、中心和颈部1/3。在非活体牙齿中，(1)发射激光的输出信号均为零，从牙齿上任何位置的记录中都看不到振荡，但(2)LDF信号在零以上，与心率有关的有规律的振荡，在牙齿的中央和颈部都记录到被动的BF增加(对应于血压增加)，表明LDF记录到了非牙髓起源的血流。在有活力的牙齿中，LDF信号在牙齿上的每个位置都显著高于非活力牙齿。在活体牙齿的中心部位，发射激光的输出信号大约是LDF的两倍，与血压升高相对应的被动BF变化更明显。这些结果表明，透射式激光对牙髓活力的评估是有用的，因为血流信号不包括非牙髓起源的血流，而且它的输出信号和对BF变化的响应更大，因此更容易监测。

The purpose of this study was to determine if use of transmitted laser light might enable a better assessment of human pulpal vitality than does back-scattered light (LDF : laser Doppler flowmetry). The experiments were carried out on 10 upper central incisors in 6 subjects aged 23-28 years ; 5 of the teeth were vital with no restoration, and 5 were non-vital. For use with transmitted laser light, the fibers within the probe of a conventional LDF apparatus were used, one for transmitting light onto the buccal surface, the other for receiving it at the palatal surface of the same tooth. For LDF,the probe was fixed at the buccal surface. Blood flow (BF) was measured at three different locations on each experimental tooth : the incisal third, the center and the cervical third of the tooth crown. In non-vital teeth, (1) output signals with transmitted laser light all registered zero, and no oscillation could be seen in recordings from any location on the tooth, but (2) LDF signals were above zero, there were regular oscillations related to heart rate, and passive increases in BF (corresponding to BP increases) were recorded from both the center and cervical third of the tooth, indicating that LDF registered blood flow of non-pulpal origin. In vital teeth, LDF signals were significantly higher than in non-vital teeth at each location on the tooth. At the central site on vital teeth, the output signals for transmitted laser light were about twice those seen with LDF,and passive BF changes corresponding to BP increases were more clearly observed. These results indicate that transmitted laser light would be useful for the assessment of tooth pulp vitality both because the blood flow signals do not include flow of non-pulpal origin, and because its output signals and response to BF changes are larger and so can be more easily monitored.