A new method for continuous in vivo pH measurement in saliva and oral biofilm - a comparative pilot study

Abstract

Background: Measuring intraoral pH is a factor in determining the pathogenicity of processes. Until now, been continuous pH measurement over a period of 96 h in parallel (saliva [S]) and established biofilm [B]) has not been feasible. This exploratory study aimed to develop a method for continuous, wireless pH monitoring of both S and B.

Methods: A wireless device with integrated pH probes was used to measure SpH and BpH in 12 participants (average age 24.28 ± 2.77 years) over a period of 96 h. Participants drank a glucose solution at three specified measurement points (G0: Baseline, G1: Glucose decline, G2: 30 min after drinking) and the 24-hour periods within the 96-hour measurement period were evaluated. The device was removed during meals and while brushing teeth.

Results: Glucose intake significantly reduced pH in both (S + B) (p < 0.001). SpH was significantly higher (G0/ G1/ G2: 6.29 ± 0.29/ 5.55 ± 0.33/ 5.79 ± 0.32) than in BpH (G0/ G1/ G2: 6.03 ± 0.33/ 5.34 ± 0.41/ G2: 5.56 ± 0.32) at all three selected measurement points (p-value at G0/ G1/ G2: p = 0.003/ p = 0.005/ p = 0.002). Regardless of glucose intake, no statistical difference was found between SpH (0–24 h/ 24–48 h/ 48–72 h/ 72–96 h: 5.86 ± 0.41/ 5.75 ± 0.37/ 5.92 ± 0.38/ 5.90 ± 0.31), BpH (5.60 ± 0.52/ 5.59 ± 0.29/ 5.77 ± 0.39/ 5.70 ± 0.46) in the time periods (p-value 0–24 h/ 24–48 h/ 48–72 h/ 72–96 h: p = 0.09/ p = 0.27/ p = 0.40/ p = 0.27).

Conclusions: The study design offers the possibility to continuously measure the pH value in S and B in the oral cavity over a period of 96 h.

Clinical relevance: This wireless method developed for measuring pH in S and B can collect data under everyday conditions and has the potential to become a patient-friendly approach for pH monitoring in the future.

Supplementary Information: The online version contains supplementary material available at 10.1007/s00784-025-06703-9.

Keywords: Caries; Erosion; Nutrition; PH value; Prevention; Real-time monitoring.

Fig. 1

Intraoral device (after 14 days of wear) on a plaster model. (a) General view. (b) Probe for measuring the pH of saliva (c) Probe for measuring the pH of biofilm

Fig. 2

(a) pH probe (CE marking: G1 094769 0011 Rev. 00, Bravo, Medtronic Deutschland GmbH, Meerbusch) and (b) Data receiver (Bravo Reflux Recorder, Medtronic Deutschland GmbH, Meerbusch)

Fig. 3

Flowchart of the subject search and selection results

Fig. 4

Reduction in pH value for both biomaterials (a) for biofilm and (b) for saliva from baseline to peak value. Baseline value Saliva/Biofilm (G0), glucose decline Biofilm/Saliva (G1), final pH (G2)