Abstract
Transmitted-light plethysmography (TLP) is an optical technique which can be used to detect microcirculatory changes in the pulp tissue. It has been known to overcome the disadvantages of the electric pulp testing in terms of the objectivity and invasiveness. In the previous study, we applied TLP system with 525 nm light emitting diode (LED) to traumatized young permanent and deciduous teeth, and found that TLP pulse amplitudes or pulse shape characteristics change gradually during clinical follow-up after the dental trauma. However, the origins of tooth plethysmogram were still not fully understood due to the structural specificity of the tooth and complex light interaction with the enamel, dentin and pulp tissue. In this study, multi-wavelength optical plethysmograph was used to examine the light transmission property of the tooth to clarify the effects of physiological parameters such as blood volume and SO2 on the pulsation of TLP pulse waves. The results indicated that the optical process in the tooth mainly depended on the blood cell concentration in the pulp chamber(Hctp), the light attenuation by the hard tissues and the light source wavelength. Clinically, it was assumed that the changes of blood vessel density, pulpal blood volume and pulp chamber size associated with subjects' age or pathological conditions might affect TLP pulse waves. In addition, SO2 changes in the pulpal blood could be detected using non-isosbestic wavelength of 467 nm qualitatively. The present results of multi-wavelength optical plethysmography explained the generation mechanism of the TLP pulse waves and potentially provided additional information to diagnose the circulatory status of the pulp in relation to pathological conditions of the dental pulp.
