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Biomedical Imaging and Instrumentation

Biomedical Imaging and Instrumentation - Poster Session E

R22 - Dentinal microcrack detection using flexible ultrasound transducers

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Addison Whitehead

Student Research Assistant
University of South Florida, United States

Co-Author(s)

Addison Whitehead

Student Research Assistant
University of South Florida, United States

Last Author(s)

AK

Albert Kim

Associate Professor
University of South Florida, United States

Primary Investigator(s)

AK

Albert Kim

Associate Professor
University of South Florida, United States

Co-Author(s)

Adam E. Major

Student Research Assistant
University of South Florida
Tampa, Florida, United States
IA

Ibrahim Al-Qraquly

Student Research Assistant
University of South Florida, United States

Introduction: : Cracked Tooth Syndrome (CTS) is a dental condition that is often overlooked [1]. An incomplete fracture of a tooth, typically affecting the enamel and dentin and sometimes extending into the pulp, can cause intermittent pain. If left undetected, the microcrack will grow, causing erosion, thermal sensitivity, and pain while chewing [1]. Due to the nature of the microcrack, visual inspection, even with the help of magnifying loupes, often fails to detect the cracks. Additional tests, such as tactile examination, percussion test, and dye test, are used in the clinic without consensus, which can be burdensome [1]. In this abstract, we present a handheld, flexible ultrasound transducer, paired with Short-Time Fourier Transform (STFT), which enables an expedited and precise diagnostic process. Inspired by non-invasive rebar detection in concrete [2], the received ultrasound exhibits a lower frequency, and a time delay compared to the transmitted one. The use of Short-Time Fourier Transforms (STFT) and Fast Fourier Transforms (FFT) gives insight into such slight frequency changes caused by the presence of a crack.

Materials and

Methods: : The flexible ultrasound transducers consist of a transmitter and a receiver. The transmitter notably features an array of four 1 × 1 × 5 mm piezoelectric elements (lead zirconate titanate or PZT; PSI-5A4E, Piezo.com). The PZT crystals are fitted into a 3D-printed elastic holder that allows them to interface the tooth contour easily. All four PZT crystals are electrically connected to pair with a signal generator, a power amplifier, and a matching circuit. For the ultrasonic receiver, we adopted a 9 cm2 square polyvinylidene fluoride (PVDF; PVDF-P0040, PolyK). A 100nm platinum layer was sputtered onto both sides of the PVDF for electrical poling. A piezoelectric coefficient, d33, was measured (D33 meter, APC International).
A signal generator outputting a burst of 3 cycles of a sinusoidal signal in a 500 µs period with a peak-to-peak voltage of 50 mV at a frequency of 15 MHz was connected to an RF power amplifier of gain 1000. This allowed the generation of ultrasound through the transmitter, which was placed against 3D-printed cracked and uncracked resin cylinders for testing. The receiver was layered on the opposite side of the test specimens. Both cracked and uncracked cylinders were 8 mm in diameter and 10 mm in height. The cracked cylinder contained a crack of ~ 250 µm in width. The PVDF receiver was connected to an oscilloscope, and the voltage data was collected. Using MATLAB, a Short-Time Fourier Transform (STFT) and a Fast Fourier Transform (FFT) were calculated to analyze the received signals.

Results, Conclusions, and Discussions:: FFT analysis of our output data revealed that the ultrasound output through the cracked cylinder had a peak frequency of 1.4 MHz, lower than that of the uncracked cylinder output; fpeak of the uncracked cylinder was 13.5MHz, whereas fpeak of the cracked cylinder was 12.1 MHz. Furthermore, both FFTs showed additional spikes of lower amplitude, near the peak frequency. This was attributed to the cracks or internal interfaces causing retard in ultrasound travel, resulting in a frequency shift towards the lower side. The ultrasound waves encountered more obstacles (i.e., internal interfaces) when passing through the cracked cylinder compared to the uncracked cylinder.
Our STFT analysis did not yield any clear indicators of cracks outside of the peak frequency shift found from the FFT analysis , but further investigation into this more complex transform could allow for more specific discrimination, such as in isolating the signal effect of a crack from the complex internal architecture of a tooth. These promising results are guiding the construction of the second prototype.
For future studies, we will design more piezoelectric elements for the transmitter. A new transmitter with flexibility in two dimensions and enhanced frequency sensitivity will be developed. A filtering and data processing circuit will also be necessary for internal frequency analysis. This will allow the device to detect cracks without manual data collection. Lastly, the final design will be fitted with a clipping mechanism to grab onto the facial and lingual sides of front teeth and buccal and lingual sides of back teeth. This will provide housing for internal circuitry and a user interface.

Acknowledgements and/or References (Optional): : [1] S. Mathew, B. Thangavel, C. Mathew, S. Kailasam, K. Kumaravadivel, and A. Das, “Diagnosis of cracked tooth syndrome,” Journal of Pharmacy and Bioallied Sciences, vol. 4, no. 6, p. 242, 2012, doi: https://doi.org/10.4103/0975-7406.100219.
[2] S. Kim, M. Kim, M. -J. Kwak, H. Hwang, S. Song and Y. Joo, "Image-Based Analysis Method for Detecting a Rebar in Concrete Using Short-Time Fourier Transform (STFT)," in IEEE Sensors Letters, vol. 8, no. 11, pp. 1-4, Nov. 2024, Art no. 2504304, doi: 10.1109/LSENS.2024.34794