Abstract
The vitality of the tooth pulp in children has been mainly determined by the response to painful stimuli such as to electrical and thermal ones. In the present study, we recorded transmitted-light photoplethysmography (TLP) from the dental pulp in children and examined its applicability to the pulp vitality test. The upper central incisors of one adult (n=2,26 y) and six children (n=12,6 healthy and 6 traumatized,6 y-12 y) were used for this investigation. Prior to the measurement, the purpose and procedure of the present study were explained to the subjects and their parents and informed consent was obtained. A resin cap of the examined tooth was prepared on the plaster model of the upper arch of the subjects. A green light-emitting diode (LED, peak power at 525 nm) 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 550 nm), and its intensity change was recorded as TLP through an AC-coupled amplifier together with the finger plethysmography of the subjects. Recordings were made with and without an opaque black rubber dam application in a dark room. TLP signals were afterwards averaged and their amplitudes were obtained using a signal processing software. In one subject,2% lidocaine solution containing 1/80,000epinephrine (2% LE) was periapically infiltrated and the transition of the amplitude of the TLP was observed. The 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 far clearer with the young subjects.2)TLP was recorded slightly from luxated teeth which did not respond to electrical stimulation to the pulp. With an implanted tooth, however, 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 sensation of pain.
