BACKGROUND: Numerous functions of saliva depend on its biophysical properties. Mouth rinses react with saliva and change both their own properties and properties of saliva. OBJECTIVE: The aim of this study was to define the level of mixing of artificial saliva and mouth rinses, define their viscosity and its changes at room and body temperature. METHODS: Artificial saliva, fluoride solutions, chlorhexidine, zinc-hydroxyapatite solution and casein phosphopeptide amorphous calcium phosphate were used. To simulate their mixing, Y-channel PVC chips were used, in two different microfluidics systems. The experiments were recorded with a microscope, then the proportion of mixing was calculated using Matlab. For viscosity measurements rotational viscometer was used. RESULTS: The results show partial mixing of all solutions with artificial saliva. Measurements on a viscometer indicate different viscosity of all used solutions. Viscosity of a mixture of solution and artificial saliva is always in the range of viscosity of the artificial saliva and the solution separately. Moreover, viscosity of all solutions, as well as mixture with artificial saliva, significantly decreases at higher temperature. CONCLUSION: Intraoral administration of mouth rinses results in change of biophysical properties of both saliva and mouth rinses. Those changes can affect preventive and therapeutic effect, and therefore oral health.

Miniaturization of different measurement processes and a scaled-down approach open the possibility for rapid measurements with the small amounts of samples and reagents into a compact platform with integrated sensors and different measuring components. In this paper, we report a microfluidic approach for measurements of salivary pH, dissolved O2, and CO2 during chewing xylitol gum. The study was done with the samples of 30 healthy volunteers who were chewing a xylitol gum, and the measurements were performed in the microfluidic (MF) chip with integrated commercial PreSens sensors. Xylitol exhibited a significant effect on the pH of saliva in terms of its initial drop, which was the most significant between the 5th and 10th minutes. The effect of xylitol on the amount of oxygen and carbon dioxide in saliva cannot be confirmed. The employed microfluidic platform was shown to be applicable and effective in the analysis of salivary biomarkers relevant to caries development.

In this paper, we propose a microfluidic approach for measuring pH, dissolved oxygen (O 2), and carbon dioxide (CO 2) in human saliva. The proposed innovative method combines the advantages of a microfluidic approach, i.e., small amounts of samples and reagents and precise control of the experimental conditions, with rapid measurements of significant parameters of saliva. The novel design of a microfluidic chip with integrated commercially available PreSens sensors was used for examining the effect of Chlorhexidine on artificial saliva (AS), stimulated saliva (SS), and non-stimulated saliva (NSS). The measurement results showed that for persons with an initially low saliva pH, the use of Chlorhexidine increased the pH, and afterward, the pH value returned to the initial value or higher. However, measurements of volunteers with initial pH close to neutral showed that Chlorhexidine reduced the pH value, increasing the risk of erosion and demineralization. In conclusion, the proposed methodology showed potential for precise measurements of pH in saliva samples; however, further research is required to examine the influence of the sample collection method on the amounts of O 2 and CO 2 in saliva.

SummaryBackground/Aim: Human saliva offers many advantages over blood-based biochemical assays, therefore, becomes the biological fluid of interest. Once antiseptic solutions react with saliva, both fluids undergo significant changes of their biophysical properties, consequently, those changes have an impact on their principal function.Material and Methods: In this study, saliva was collected and mixed with 0,1% chlorhexidine digluconate solution, fluoride mouthwash, zinc-hydroxyapatite solution and CPP-ACP paste. Microfluidic PVC/Green tape chips within the experimental setup were used to simulate solution mixing. The chip had 2 inlets and 1 outlet, and channel was designed in Y shape without any obstacles. The inlet channels were set at a 60° angle. The channel width was 600 µm and the diameter of inlets and outlet was 2 mm. For better visualization, blue food coloring was added to the saliva. The procedure was recorded with digital USB microscope camera and afterwards the percentage of mixing was obtained by MATLAB programming language.Results: Obtained results show incomplete mixing of all the solutions with saliva. The value of mixed liquid, when mixing 0,1% chlorhexidine digluconate solution with saliva was 51,11%. In case of medium concentration fluoride mouthwash, result was 84,37%. Zinc hydroxyapatite solution obtained result of 85,24%, and the fourth tested solution, CPP-ACP paste, 83,89%.Conclusions: Analyzed mouthwashes exhibit specific, non uniform behavior during mixing with saliva. Microfluidic setups could be efficiently used in simulating real clinical conditions in laboratory settings. Image processing mathematical models are applicable, accurate and useful in determination of the interaction of saliva with commonly used antiseptic solutions.