Dental News - “Colleagues challenged me to predict where caries might occur in the mouth”

Anisha Hall Hoppe, Dental Tribune International

Tue. 31. May 2022

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A new prototype device paves the way for pinpointing exactly where acidity in oral biofilm is increasing and thus where caries is most likely to develop. The optical pH monitor, called O-pH, has provided impressive results in monitoring oral biofilm pH levels and has even influenced the career path of one of its developers. Dental Tribune International (DTI) was able to speak with lead researchers Dr Eric Seibel, research professor of mechanical engineering with department affiliations in electrical and computer engineering, bioengineering and oral health sciences at the University of Washington, and doctoral student Manuja Sharma about the development of the O-pH device, its potential and the motivation behind the project.

Ms Sharma, DTI previously reported on the new prototype optical pH sensor O-pH. How has developing a dental device as an electrical and computer engineering PhD student influenced your studies and your targeted career path?
Sharma: On a personal level, my research has motivated me to work in health diagnostics in order to design and develop sensors to investigate the signals and parameters of the human body that are, as yet, unexplored. In the development of O-pH, I had an opportunity to interact with dentists, chemists and other engineers and understand what it takes to build a prototype and deliver it to the clinic. I am sure that these skills and experiences will be extremely valuable in the course of my future career.

Dr Seibel, the study mentioned that previous attempts at measuring dental biofilm pH utilised electrodes or pH strips. How did your team come up with the revolutionary concept of using photodiodes?
Dr Seibel: My dental colleagues challenged me to predict where caries might occur in the mouth, which led me to measure pH, not at the outside of the oral biofilm, bathed by saliva, as done by pH electrodes or paper pressed up against the biofilm, but throughout the biofilm. This requires a pH-sensitive dye that permeates only the extracellular matrix in order to obtain an accurate reading of the pH that surrounds enamel.

Sharma: The low-power blue light makes the dye inside the syringe fluoresce, and then this dye on an artificial tooth set mimics how the device works in the mouth.

The O-pH device utilises a low-power blue light and a special dye to cause oral biofilm to fluoresce in areas with higher levels of acidification. (Image: Manuja Sharma, University of Washington)

Case study employing multi-modal scanning fibre endoscope (mm-SFE) for pH sensing. The subject had not received professional cleaning for over seven months and had skipped brushing for five days prior to the examination. (a) Interproximal dental biofilm image with pH heat map. (b) The pH heat map after sugar rinse. (c) The difference between rest pH and drop pH. (d) The protocol used for testing with mm-SFE. Fluorescein is rinsed instead of applied on each tooth surface using a blunt hypodermic needle. (e) The mm-SFE pH probe. (f) The Stephan curve, red line indicating average pH obtained using images at each stage of rest pH and drop pH. (Image: University of Washington)

Doctoral student Manuja Sharma is studying electrical and computer engineering; she has found that her work on the O-pH device has oriented her towards developing medical diagnostic devices. (Image: Manuja Sharma)

Dr Eric Seibel is research professor of mechanical engineering and adjunct research professor of electrical and computer engineering, bioengineering and oral health sciences at the University of Washington. (Image: Eric Seibel)

During your research with O-pH, did you identify any other opportunities for further research other than that of investigating different levels of sucrose concentration?
Dr Seibel: We have been pursuing a dental app that would help guide a teenager undergoing orthodontic treatment, or his or her parent, in applying prescription-level fluoride varnish at home for the locations that are identified as highest risk for caries by O-pH. This concept was tested in surveys of paediatric dentists in Washington State and presented in a poster of which Ms Sharma was a co-author.

What is the next step for this product, and what would it take to make it widely available for use by practitioners?
Dr Seibel: We hope to work with dental device manufacturers to conduct clinical studies with variations of the O-pH device, such as the image-based device—multi-modal scanning fibre endoscope—used in the case study described in our recently published paper. An imaging system that maps oral biofilm pH should be able to achieve a more robust measurement over time. For example, one set of panoramic images of the pH of the biofilm covering enamel surfaces can be compared with the next set of panoramic images obtained six months later. Over time, this measurement of the biofilm pH before the biofilm is removed at the dental clinic can become a quantitative and spatial enamel health monitoring system.

Editorial note:

Both researchers said they could envision a smaller version of their O-pH device being used at home to help dental patients see biofilm and monitor acidification on their teeth, perhaps in conjunction with such an app as Dr Seibel previously mentioned.

The poster Manuja Sharma presented for the 2022 University of Washington Electrical and Computer Engineering Research Showcase can be found here, and further information on the presentation can be found here.

The original published study referenced by Dr Seibel, titled “O-pH: Optical pH monitor to measure oral biofilm acidity and assist in enamel health monitoring”, was published online on 23 February 2022 in IEEE Transactions on Biomedical Engineering, ahead of inclusion in an issue.