Objectives: Several methods are available to indirectly measure the vitality of the human tooth pulp tissue in vivo. Pulse signals detected directly from the pulp might be considered reliable for an objective assessment of pulp vitality. The purpose of the present study was to design an in vitro model for measurements of blood pulsing through a human tooth.

Methods: A cylindrical hole was cut in occlusal-apical direction into the center of a human molar crown. A silicon tube (outer/inner diameter: 2.0/1.0 mm) was placed through the hole and connected to a flexible-tube pump (Multifix). An individually designed sensor (infrared light emitter: SFH409, 950nm, Osram, Germany; detector: SFH229FA Photodiode, 880nm, Siemens, Germany) was applied lingual-buccaly to the crown. Air, tap-water, algae (Chlorella 1000µg/l, 685nm), and human erythrocyte-concentrate were pulsed through the tube in two frequencies (F1:3/sec; F2:5/sec) and detected by an individually designed dual channel photopletysmograph. Signals were recorded using an oscillograph (Tektronix TDS2022B, Tektronix Inc., Beaverton, USA), and test parameters Signal-Intensity [Volt] and Signal Duration [ms] were derived. Reference measurements were taken from the tube without surrounding tooth structure. Five samples per experimental group were statistically treated applying non-parametric procedures (a=0.05). 

Results: At all reference measurements F1 and F2 frequencies were detected. Air and tap-water were not detected. Signal duration of algae and erythrocyte-concentrate was for F1 330ms-350ms and for F2 160ms-180ms. Results of the Signal-Intensity measurements (Medians with 25-75% Percentiles) were as follows:

	Signal-Intensity, F1 [Volt]	Signal-Intensity, F2 [Volt]
Algae	9.0(9.0-9.5)	7.0(7.0-7.2)
erythrocyte-concentrate undiluted	11.0(11.0-11.0)	9.5(9.5-9.5)
erythrocyte-concentrate 1:10 diluted	12.5(12.5-12.8)	8.0(8.0-8.0)
erythrocyte-concentrate 1:100 diluted	12.0(11.8-12.0)	6.500(6.5-7.0)

The  decrease of Signal-Intensity with increasing dilution of erythrocyte-concentrate at F2 was statistically significant, as well as the Signal-Intensity at F1 compared to F2.

Conclusions: This in vitro system turned out to be suitable to detect pulsing blood through tooth structure.

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