BACKGROUND This study compared the difference in pulpal blood flow between vital and root-filled teeth by using ultrasound Doppler imaging. METHODS To compare the difference in pulpal blood flow between vital and root-filled teeth, 11 patients (mean age, 32.06 years; 3 male, 8 female) who had undergone root canal treatment on the anterior tooth of the maxilla or mandible and had a vital contralateral tooth were examined. Pulpal blood flow measurements were performed on the vital and root canal-treated teeth by using ultrasound Doppler imaging. The parameters examined were the maximum linear velocity (Vas), average linear velocity (Vam), minimum linear velocity (Vakd), pulsation index (PI), and circulation resistance (RI), which are indicators of the pulpal blood flow. The differences between the vital and root-filled teeth were examined by using a paired t test at the 95% confidence interval. RESULTS There were significant differences in the Vas, Vam, Vakd, and RI between the vital and root-filled teeth (P<.05). With the root-filled teeth, ultrasound Doppler imaging revealed a linear and nonpulsed waveform, whereas the vital teeth showed a pulsed waveform that is characteristic of an arteriole. CONCLUSIONS Ultrasound Doppler imaging can detect pulpal blood flow in vital tooth through indicators such as Vas, Vam, Vakd, PI, and RI.