The Incisor Interviews UW researcher Dr. Eric Seibel on Newly Developed Dental Prototype

The Incisor sits down with University of Washington researcher Dr. Eric Seibel to discuss his latest project, the O-pH prototype, aimed at early detection of dental caries.

By Genni Burkhart

While dentists have plenty of technology and tools at their disposal for the detection of dental caries, detecting the specific acidic conditions that lead to dental caries (and preventing them in the first place) is much more difficult.

Emitting LED light, the O-pH system is a prototype optical device that measures the reactions of the light and fluorescence with the use of FDA-approved chemical dye that’s applied to teeth. From this, the O-pH can produce a numerical reading of the pH plaque that covers the targeted teeth. Dentists, then knowing the acidity level of the plaque of each tooth, can use this information for targeted treatments and educating the patient on what tooth is most at risk of developing a cavity and thereby prevent it.

Recently publishing the study, O-pH: Optical pH Monitor to Measure Oral Biofilm Acidity and Assist in Enamel Health Monitoring 1 , lead researcher at the University of Washington (UW) Dr. Eric Seibel, PhD spoke with The Incisor about the O-pH prototypes and how he hopes dentists can use this target treatment tool to further the oral health of patients.


Incisor: With a background in Mechanical and Bioengineering, what interests you about research and innovation in oral healthcare and dentistry?

Seibel: There are many aspects of traditional dental technologies that overlap with mechanical and material science engineering; however, I am fascinated by the reliance on direct visual examination by the dentist and the fact that enamel remineralizes, so there’s a goal of using restorations as a necessary (but last resort) when managing caries.

Incisor: Can you talk about other research projects you're working on such as the ultrathin and flexible scanning fiber endoscope (SFE)?

Seibel: This O-pH project is one in a series that started with using the small SFE by using its unique properties with imaging the enamel. We’ve used blue light to see the surface and excite autofluorescence, porphyrin fluorescence, and now pH-sensitive dyes. Outside of the visible spectrum, we’ve used infrared light to see more deeply into enamel. In the future the SFE will be made smaller (less than 1.0 mm diameter), better allowing it to fit into drilled holes in teeth and between the gum and root.

The SFE was invented to image in regions of the human body that were previously inaccessible using current flexible scopes to guide interventions. It’s been used to guide biopsies of endoscopically invisible cancers in the esophagus with fluorescence biomarkers in a couple clinical trials at the University of Michigan.

Incisor: What skills are unique to your research team at The University of Washington (UW)?

Seibel: First of all, I always work together with the dental experts in the Seattle area. This started out with my local dentist Dr. Michal Friedrich and the Chair of UW Pediatric Dentistry, Dr. Joel Berg, DDS, MS, along with his excellent colleagues. Currently my main collaborator is Alireza Sadr, DDS, PhD Clinical Associate Professor, Restorative Dentistry. Our unique skills come from applying engineering skills with a passion for learning about the unmet needs and problems faced by dentists and dental hygienists.

Dr. Eric Seibel, PhD

Incisor: The O-pH device was tested on pediatric patients, but is the intent to use it on dental patients of all ages?

Seibel: Yes, but when we use the SFE, its small size makes it ideal for children. Also, my initial collaborators were in pediatric dentistry.

Incisor: Explain the prototype and process for the O-pH to our readers.

Seibel: The O-pH prototype is really two optical instruments ­– one senses pH from a pointed beam of light and the SFE which images pH from a scanned field of view, all done rapidly with a low concentration of fluorescein yellow dye and without contact to the oral biofilm. The three optical signals are detected by a computer and pH is calculated from these known locations in the mouth.

Incisor: How did this particular research project come into design?

Seibel: I was challenged by University of Washington (UW) Zheng Xu, DMD, PhD to not just detect caries, but to also predict where they’ll develop. I then spoke with an expert in oral biofilms at UW, Jeffrey Scott McLean, PhD Associate Professor Periodontics and he stated pH needs to be measured at or near the enamel surface. I knew fluorescein rapidly diffuses into biofilms and is pH sensitive, but I was unsure that it could be used accurately. However, it’s a safe first molecule since it was approved by the Food and Drug Administration (FDA). I then recruited to the project retired chemist Dr. Len Nelson PhD who volunteers his time working with UW students doing research in my lab. Len is also an inventor, and he delivered a novel method to measure intraoral pH accurately and robustly. Dr. Len Nelson, two students, and I are all on this particular UW patent filing.

Incisor: What are the current changes you're making to the prototype after concluding this study?

Seibel: The point-based pH sensing has moved to an image-based pH mapping of oral biofilms, but the readout of pH as an overlay or heatmap needs to be computed quicker through the use of a more sophisticated software pipeline and improved computer power. Further clinical studies are also needed.

Incisor: What is the most beneficial aspect of the O-pH for dentists as well as the patient?

Seibel: The greatest benefit to dentists will be discovered once this technique can be done easily and rapidly by the hygienist, when the patient first sits in the dental chair. Then the undisturbed biofilm pH mapping can be interpreted accurately and quickly by just a glance on the display from the dentist as they’re examining cleaned and polished teeth.

The utility of the image-based O-pH may be the quantitative biofilm pH mapping with clinical validated thresholds for pH values that may trigger remineralization therapies, or changes in oral hygiene by the patients. If the O-pH values are taken after teeth cleaning, then another set of thresholds may be the only measurement the dentist has of active caries.

The patient should also be able to benefit by delaying loss of pristine enamel protection from drilling and filling, allowing the integrity of the natural enamel to stay healthy and remineralized longer and throughout their lifetime with the O-pH measurements.

And finally, it’s possible the relationship between the patient and dentist could move outside the clinic as more at-home therapies are prescribed by the dentist and monitored by smartphone apps. Patients could become more invested in their oral health as they witness themselves the production of acid from their own oral biofilm microorganisms.

Incisor: Can you correlate a certain level pH with a particular strain of biofilm, or does the O-pH illuminate all oral microorganisms?

Seibel: O-pH doesn’t discriminate on the specific species of bacteria by providing a functional measure (biofilm pH) that is mapped across all the enamel surfaces. All oral microorganisms are being imaged for their resulting extracellular pH.

Incisor: What is most important to note from this study, and how can this information be used in the progress to advance oral healthcare through patient education and understanding of oral health disease?

Seibel: The initial clinical study of the O-pH (point-based pH sensing) was promising but there were significant limitations. In the study publication, one challenge of repeatable probe placement was addressed by changing over to an image-based pH mapping instrument, but results were only presented for a case study, single subject. In addition, the O-pH patient selection was improved by having patients with over 3 months since their last teeth cleaning. Finally, the protocol has been simplified with using just one rinse of the pH-sensitive dye solution for mapping resting biofilm pH of all enamel surfaces.

We appreciate the interest in this new oral biofilm pH mapping technology and clinical procedure which has the potential to provide dentists and patients with a quantitative measure of oral health and a leading indicator of early caries.

It’s my hope that clinical dentistry –being a cross-section of applied art, science, and engineering – will allow dentists to be early adopters of new technologies like O-pH when compared to more traditional branches of healthcare.


  1. Sharma, M., Lee, L. K., Carson, M. D., Park, D. S., An, S. W., Bovenkamp, M. G., Cayetano, J. J., Berude, I. A., Xu, Z., Sadr, A., Patel, S. N., & Seibel, E. J. (2022). O-pH: Optical pH Monitor to Measure Oral Biofilm Acidity and Assist in Enamel Health Monitoring. IEEE transactions on bio-medical engineering, PP, 10.1109/TBME.2022.3153659. Advance online publication.


Author: With over 12 years as a published journalist, editor, and writer Genni Burkhart’s career has spanned politics, healthcare, law, business finance, technology, and news. She resides on the western shores of the idyllic Puget Sound where she works as the Editor in Chief for the Incisor at DOCS Education out of Seattle, WA.

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