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Objective: Bacteria in the dental biofilm produceacid after consumption of carbohydrates which if left unmonitored leads to caries formation. We present O-pH, a device that can measure dental biofilm acidity and provide quantitative feedback to assist in oral health monitoring. Method: O-pH utilizes a ratiometric pH sensing method by capturing fluorescence of Sodium Fluorescein, an FDA approved chemical dye. The device was calibrated to a lab pH meter using buffered fluorescein solution with a correlation coefficient of 0.97. The calibration was further verified in vitro on additional buffered solution, artificial, and extracted teeth. An in vivo study on 30 pediatric subjects was performed to measure pH before (rest pH) and after (drop pH) a sugar rinse, and the resultant difference in pH (diff pH) was calculated. The study enrolled subjects with low (Post-Cleaning) and heavy (Pre-Cleaning) biofilm load, having both unhealthy/healthy surfaces. Further, we modified point-based O-pH to an image-based device using a multimode-scanning fiber endoscope (mm-SFE) and tested in vivo on one subject. Results and Conclusion: We found significant difference between Post-Cleaning and Pre-Cleaning group using drop pH and diff pH. Additionally, in Pre-Cleaning group, the rest and drop pH is lower at the caries surfaces compared to healthy surfaces. Similar trend was not noticed in the Post-Cleaning group. mm-SFE pH scope recorded image-based pH heatmap of a subject with an average diff pH of 1.5. Significance: This work builds an optical pH prototype and presents a pioneering study for non-invasively measuring pH of dental biofilm clinically. [ABSTRACT FROM AUTHOR]

Sugar-rich diets and poor dental hygiene promote the formation of a biofilm (plaque) that strongly adheres to the dental enamel surface and fosters the evolution of aciduric bacteria. The acid contributes to demineralization of the exterior tooth enamel, which accelerates after the pH drops below a critical value (~5.5) for extended time periods resulting in the need for restorative procedures. Preventative techniques to alert the dentist and caries-susceptible patients regarding vulnerability to dental decay require a clinical measure of plaque activity. Therefore, there is a need to evaluate the acid production capability of plaque deposits in the pits and fissures of occlusal and interproximal regions. A ratiometric fluorescence pH-sensing device has been developed using an FDA-approved dye and LED excitation. Fluorescein spectral profiles were collected using a spectrometer and analyzed with a spectral unmixing algorithm for calibration over the pH range of 4.5 to 7. An in vivo pilot study on human subjects was performed using a sucrose rinse to accelerate bacterial metabolism and to measure the time-dependent drop in pH. The optical system is relatively immune to confounding factors such as photobleaching, dye concentration, and variation in excitation intensity associated with earlier dyebased pH measurement techniques. [ABSTRACT FROM AUTHOR]

The Stephan Curve has played a dominant role in caries research over the past several decades. What is so remarkable about the Stephan Curve is the plethora of interactions it illustrates and yet acid production remains the dominant focus. Using sophisticated technology, it is possible to measure pH changes in plaque; however, these observations may carry a false sense of accuracy. Recent observations have shown that there may be multiple pH values within the plaque matrix, thus emphasizing the importance of the milieu within which acid is formed. Although acid production is indeed the immediate proximate cause of tooth dissolution, the influence of alkali production within plaque has received relative scant attention. Excessive reliance on Stephan Curve leads to describing foods as 'safe' if they do not lower the pH below the so-called 'critical pH' at which point it is postulated enamel dissolves. Acid production is just one of many biological processes that occur within plaque when exposed to sugar. Exploration of methods to enhance alkali production could produce rich research dividends. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The aim of the present investigation was to evaluate the caries susceptibility of endodontically versus nonendodontically treated teeth in relation to dental plaque–related factors. Methods: Twenty patients with 2 endodontically treated teeth (ETT) each were examined regarding cariogenic microflora of proximal plaque, in situ plaque pH drop after a sucrose rinse (Stephan curve), and de novo plaque formation. Recurrent caries and the quality of the coronal fillings/crowns of these teeth were also evaluated. ETT were compared with contralateral, nonendodontically treated teeth (NETT). Results: Irrespective to the type of restoration, Streptococcus mutans count, de novo plaque formation, and recurrent caries were higher on the surface of ETT compared with NETT (P < .05). Moreover, the initial (resting) pH in plaque was significantly lower (P < 0.05) in ETT. Conclusions: ETT showed an increased susceptibility to caries as a result of either alteration in their biological environment or inadequacy of the marginal fit of the dental restoration. Clinicians should be aware of this risk. [ABSTRACT FROM AUTHOR]