A laboratory study to detect simulated pulpal blood flow in extracted human teeth using ultrasound Doppler flowmetry.

AIM To develop a laboratory-based tooth model of simulated blood flow in teeth and evaluate it using ultrasound Doppler flowmetry (UDF). METHODOLOGY A laboratory-based tooth model for UDF was created based on a microfluidic phantom proposed by Kim & Park (2016). Twenty-one maxillary or mandibular anterior human teeth within one month of extraction were used. Four holes in each tooth including those at the apical foramen, palatal surface in the center of the crown, palatal surface apical to the cementoenamel junction (CEJ) and the root centre, were made to fit a 1.6mm diameter polytetrafluoroethylenen (PTFE) tube. Fluid mimicking pulsating blood was pumped (pressure range: 0-200 mbar, flow rate range: 0-80 μL/min) into the apical foramen via the PTFE tubes, which exited the tooth through the palatal surface in the crown centre (control group), palatal surface underneath CEJ (group 1), and the palatal surface at the mid-root level (group 2). An UDF transducer of 20MHz was placed at a 60° angle to the labial surface of tooth and was used to measure the fluid flow velocity (Vs,Vas,Vm,Vam,Vd, Vad, and Vakd). The flow velocity of the different groups was compared using the Wilcoxon signed-rank test, with a 95% confidence level. RESULTS UDF facilitated the detection of the simulated pulpal blood flow in the control group and group 1, but not in group 2. The mean and standard deviations of Vas, Vam, Vakd were 0.921±0.394 cm/s, 0.479±0.208 cm/s, and 0.396±0.220 cm/s, respectively, in the control group, and 0.865±0.368 cm/s, 0.424±0.215 cm/s, and 0.487±0.279 cm/s, respectively, in group 1. The pulpal blood flow values of the control group and group 1 were not significantly different (p>0.05). CONCLUSIONS This laboratory study showed that the UDF enabled the detection of simulated blood flow under the cemento-enamel junction level but not at the mid-root level.