A study on a noninvasive pulp diagnostic method using transmitted light photoplethysmography

点击翻译按钮获取中文摘要

In order to construct an optimal detection system for the transmitted light, light transmittance characteristics of the human extracted teeth and the human peripheral blood were investigated between 400 and 800 nm using a spectrophotometer. A tungsten incandescent light and a CdS-CdSe photoconductive cell were used as the light source and the photodetector, respectively. The spectrum analysis showed that the light of its wavelength shorter than 600 nm was more absorbable by the blood than the longer wavelength.Transmitted light photoplethsmography (TLP) was applied to vital human upper central incisors of healthy volunteers. Three different light sources (the tungsten light, a LED with its peak at 565 nm (LED565) and a LED with its peak at 695 nm (LED695)) were used as the light source. The light illuminated the palatal surface of the tooth crown and the transmitted light was collected form the labial side. The Cds-CdSe photoconductive cell was used as the photodetector. Pulse waves were observed on most of the examined teeth with the LED565, however, it was difficult to recognise the pulse wave with the tungsten light and the LED695 The results indicated the LED565 was suitable for the pulpal TLP.Then, the detectable area of the root pulp blood flow by our method was assessed. Human extracted upper central incisors were used to determine the transmitted area of the light. An LED (intensity peak 565 nm) and an optical fiber (o.d.2.2 mm) were placed in contact with the palatal and the labial surface of the teeth approximately 2 mm from the enamel-cement junction, respectively. The transmitted light throught the teeth was guided to the CdS-CdSe photoconductive cell (peak sensitivity 560nm) via the optical fiber. The results indicated that our method can detect the root pulp blood flow as far as app.2 mm from the enamel-cement junction.