Human Photonics Laboratory

Dental Health

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At HPL, new frontiers are being explored in caries management through the combination of optical and fluorescent spectroscopy procedures. In using these techniques, the process of dental decay can be detected at the earliest stages through screening. Through further research and testing, this screening process may extend to prediction of dental decay from patterns over time by measuring the acid from plaque. If demineralization of the enamel is suspected, then a quantitative diagnosis can be made, alongside therapy that preserves the natural integrity of the tooth that can be monitored safely using these devices.


The range of new techniques that have been pioneered at HPL is as listed:

Instrumental to these new techniques has been the scanning fiber endoscope (SFE) technology. There are three main applications of SFE:

  • Full color video + fluorescent spectroscopy
  • Grayscale video + optical ph mapping
  • Multi wavelength infrared video
    More on SFE can be read here.

Caries Screening/Prediction

The current dental technology regarding screening and preventing dental decay is lackluster, which is one of the problems we are attempting to solve at HPL. Our new device, Cavifree, aims to solve this problem by using an optical pH measurement system. When teeth are exposed to sugars, a reaction occurs between the sugar and bacteria on the tooth’s surface, resulting in a corrosive acid that dissolves the enamel in teeth. This decay caused by the acid speeds up after a certain pH threshold, meaning that there is a correlation between pH levels of the teeth and susceptibility to caries: those who have a higher susceptibility will exhibit lower pH values following exposure to sugar and require much longer time for the pH balance to recover. In order to track these pH values, Cavifree utilizes measurements based on the natural autofluorescence of the teeth and the fluorescein emission intensity during different stages, including: resting, immediately after a sugar rinse (drop in pH), and in 3-minute intervals after the rinse to observe the recovery.

Relevant publications:

  1. M. Sharma, J. Y. Graham, P. A. Walczak, R. M. Nguyen, L. K. Lee, M. D. Carson, S. N. Nelson Leonard Y. Patel, Z. Xu, and E. J. Seibel, “Optical pH measurement system using a single fluorescent dye for assessing susceptibility to dental caries,” Journal of biomedical optics, vol. 24, iss. 1, p. 17001, 2019. Web link

White Spot Screening

Early signs of enamel caries lesions or demineralization are seen as “white spot lesions” (WSLs), which have become increasingly common among children. If detected early, dentists can use non-surgical options to treat the WSLs before it progresses to the point where it is no longer an option. However, the current methodology in which WSLs are detected have multiple faults in them: visual and tactile exams are subject to biases of the examiner and are limited to only the exposed surfaces, intra-oral radiography isn’t as capable at detecting early-stage caries, and there are risks involved with each of these methods in damaging the surfaces where the lesions are present. Therefore, there is a great demand for a new caries detection technique that allows for real-time imaging to address all these problems. We have decided to use scanning fiber endoscope (SFE) technology to solve this, since studies have shown that SFE can be used to non-destructively image tooth demineralization. Our studies have shown that enamel caries lesions can indeed be differentiated from healthy enamel by using the near-infrared SFE imaging techniques.

The scanning fiber endoscopy (SFE) technology has been applied to near-infrared dental imaging for detection of carious lesions and quantifying demineralization. The longer wavelength of near-infrared (NIR) light has lower attenuation from scattering in enamel than visible light. Furthermore, the carious lesions appear brighter than background in reflection mode imaging due to increasing scattering coefficient caused by demineralization, with less interference from stains and non-calcified plaque. Thus, it’s a great alternative to visual and tactile examinations and especially radiography which have limitations on specificity, sensitivity and safety. However, the current NIR cameras in the 1300-1600 nm range suffer from bulky size and can’t move around within the oral cavity to acquire optimal perspectives. SFE has the advantages of miniature probe size (rigid length of 9mm, diameter of 1.2 to 2.4mm), flexible shaft, low cost and sufficient resolution (~150um) and field of view (60 degrees). Thus, SFE is a great candidate for miniature, low-cost NIR imaging system. A multispectral NIR SFE system with 1310nm, 1460nm, 1550nm laser diode channels as well as a 1310nm SLD channels is developed in Human Photonics Lab. Quantitative study was conducted on ex-vivo imaging of artificial early lesions where demineralization is created at shallow depth of polished bovine enamel. SFE reflection imaging with 1310nm and 1460nm was able to detect demineralization with sensitivity of 96% and specificity of 85% – having a moderate positive correlation with microCT measurements (gold standard) [1]. In a companion study, ex-vivo occlusal-view imaging of 19 deep artificial interproximal lesions on extracted human teeth were imaged and compared to optical coherence tomography (OCT) and microCT as the gold standard. This study showed that NIR SFE can detect interproximal lesions buried under enamel layer with thickness up to 4mm. Diagnosis from a non‐blinded trained user by looking at real‐time occlusal‐side NIR SFE videos indicate true positive rate of 78.9% and false positive rate of zero [2]. Furthermore, to improve the ease of use for this dental imaging modality for monitoring the healing process within enamel (remineralization), we developed a novel system for AR-assisted visualization and guidance for dental imaging of lesions based on OCT, SFE and Magic Leap One AR headset.

Relevant publications:

  1. Lee, R.C.; Zhou, Y.; Finkleman, S.; Sadr, A.; Seibel, E.J. Near-Infrared Imaging of Artificial Enamel Caries Lesions with a Scanning Fiber Endoscope. Sensors 2019, 19, 1419. Web link
  2. L. Zhang, A. S. Kim, J. S. Ridge, L. Y. Nelson, J. H. Berg, and E. J. Seibel, “Trimodal detection of early childhood caries using laser light scanning and fluorescence spectroscopy : clinical prototype laser light scanning and fluorescence spectroscopy :,” Journal of biomedical optics, vol. 18, iss. 11, p. 111412–1 – 111412–8, 2013.

Diagnosis with Fluorescent Spectroscopy (patented)

Relevant publications:

  1. L. Zhang, L. Y. Nelson, and E. J. Seibel, “Spectrally enhanced imaging of occlusal surfaces and artificial shallow enamel erosions with a scanning fiber endoscope.,” Journal of biomedical optics, vol. 17, iss. 7, p. 76019, 2012. Web link
  2. L. Zhang, L. Y. Nelson, J. H. Berg, J. M. Eichenholz, and E. J. Seibel, “Optical Measure of Enamel Health: Ability to Triage High Risk Children in Communities without Dental Practitioners,” 2012 ieee global humanitarian technology conference, p. 345–349, 2012. Web link

Therapy Monitoring & Guidance

Relevant publications:

  1. Y. Zhou, R. C. Lee, S. Finklemen, A. Sadr, and E. J. Seibel, “Near-infrared multispectral endoscopic imaging of deep artificial interproximal lesions in extracted teeth,” Lasers in surgery & medicine, iss. 2, 2019. Web link