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Researchers present new device for measuring dental biofilm acidity

O-pH, a dental tool newly developed by University of Washington researchers, uses blue light and a special dye to help dentists track acidification of biofilm on teeth. (Image: RomanR/Shutterstock)

SEATTLE, US: Current diagnostic tools measure the presence of caries, rather than assessing the risk of developing caries. Routine monitoring of the acid production of dental biofilm can help understand pH changes as a risk indicator of caries. Seeking to improve oral health mointoring, researchers from the University of Washington have come up with a novel way of measuring the pH level of oral biofilm that enables practical tracking of the acidification of the biofilm, a feat that previous methodologies have not achieved satisfactorily.

The prototype optical pH sensor, O-pH, was developed by a team led by Dr Eric Seibel, research professor of mechanical engineering at the university, and Manuja Sharma, a doctoral student in the university’s Department of Electrical and Computer Engineering. The device uses blue light to excite fluorescein dye and collects the fluorescent light emitted. Fluorescein dye quickly and effectively enters the extracellular matrix of the biofilm, and its emission intensity is directly proportional to the extracellular biofilm. O-pH measures pH in the average range for dental biofilm, from 4.0 to 7.5.

In a press release, Sharma explained, “This acid is what causes the corrosion of the tooth surface and eventually cavities. So, if we can capture information about the acidic activity, we can get an idea of how bacteria are growing in the dental biofilm, or plaque.”

The O-pH device provides a non-invasive and practical way for dentists to monitor enamel health with the aim of caries prevention. (Image: University of Washington and IEEE Xplore/Creative Commons)

The researchers tested the device in an in vivo study on 30 paediatric subjects in order to establish clinical relevance of dental biofilm pH and to develop a suitable protocol for standard clinical use of the device.

“We do need more results to show how effective it is for diagnosis, but it can definitely help us understand some of your oral health quantitatively,” said Sharma. “It can also help educate patients about the effects of sugar on the chemistry of plaque. We can show them, live, what happens, and that is an experience they’ll remember and say, OK, fine, I need to cut down on sugar!”

Although existing devices use blue light to excite the porphyrin that exists in oral biofilm and then capture that fluorescence, their success is limited to only a few bacterial groups found in the mouth that produce porphyrin, thus ruling out over 700 other microbes that comprise biofilm.

Other devices use LEDs, computer algorithms and cameras to help dental patients better see biofilm and motivate better oral hygiene, but none on the market are able to effectively track the actual acidification of the biofilm. It is knowing the pH levels that is key, as the presence of biofilm itself does not mean that the bacteria causing it are harmful or that it will cause caries.

The team intends to pursue the research further by incorporating imaging to indicate high-acid areas.

The study, 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.

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