POSSIBLE APPLICATION OF TRANSMITTED LASER-LIGHT FOR THE ASSESSMENT OFHUMAN PULPAL VITALITY

The purpose of this study was to determine whether use of transmitted laser light would enable a better assessment of human pulpal vitality than back-scattered light does (LDF: laser Doppler flowmetry). The exp eriments were carried out on ten upper central incisors in six subject s aged 23-28 years; five of the teeth were vital with no restoration, and five were non-vital. For use with transmitted laser light, the fib ers within the probe of a conventional LDF apparatus were used, one fo r transmitting light onto the buccal surface, the other for receiving it at the palatal surface of the same tooth. For LDF, the probe was fi xed at the buccal surface. Blood flow was measured at three different locations on each experimental tooth: the incisal third, the center an d ther cervical third of the tooth crown. In non-vital teeth, 1) outpu t signals with transmitted laser light all registered zero, and no osc illation could be seen in recordings from any location on the tooth, b ut 2) LDF signals were above zero, there were regular oscillations rel ated to heart rate, and passive increases in blood flow (corresponding to blood pressure increases) were recorded from both the center and t he cervical third of the tooth, indicating that LDF registered blood f low of non-pulpal origin. In vital teeth, LDF signals were significant ly higher than in non-vital teeth at each location on the tooth. At th e central site on vital teeth, the output signals for transmitted lase r light were about twice those seen with LDF, and passive blood flow c hanges corresponding to blood pressure increases were more clearly obs erved. These results indicated that transmitted laser light would be u seful for the assessment of tooth pulp vitality both because the blood flow signals did not include flow of non-pulpal origin, and because i ts output signals and response to blood flow changes were clear and co uld easily be monitored.