Photoacoustic waves from hemoglobin solutions in dental roots are detected by using a 1064-nm laser and an ultrasonic soft probe based on a composite transducer on the tooth surface. The high-frequency ultrasonic waves are detected from a tooth with a hemoglobin solution in the pulp cavity due to the large heat transfer coefficient and absorption coefficient of hemoglobin. The spectral intensities of frequency components higher than 1 MHz show good correlation with the hemoglobin solution concentrations, and maps of frequency spectra calculated by taking short-time Fourier transforms clearly exhibit the effect of absorbance in dental pulp.
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