Monitoring of saliva pH using miniaturized sensing tools as an indicator of oral health

The monitoring of oral disease is important, not alone for oral health, but for the detection and prevention of<br/>systemic disease. The link between oral health and systemic disease is the focus of many studies, with<br/>indications emerging of a causal link [1]. For disease diagnostics, blood has typically been the fluid of choice<br/>for analysis, the retrieval of which is invasive and therefore unsuitable for wearable technology. Analysis of<br/>saliva, however, is less invasive than that of blood, requires little or no pre-treatment and is abundantly<br/>available. A strong correlation has been found between the analytes of blood and saliva [2] with saliva<br/>containing biomarkers for diseases such as diabetes, oral cancer and cardiovascular disease. The development of<br/>an implantable multi-parametric wireless sensor, to monitor both salivary analytes and changes in gingival<br/>temperature, is the aim of this research project.<br/>The aim of our current study is to detect changes in salivary pH, using a gold electrode with a pHsensitive<br/>iridium oxide layer, and an Ion Sensitive Field Effect Transistor probe. Characterisation studies were<br/>carried out in artificial saliva (AS). A salivary pH of between 4.5pH-7.5pH [3], and gingival temperature<br/>between 35°C-38°C [4], were identified as the target range of interest for the human oral environment. Sensor<br/>measurements were recorded in solutions of varying pH and temperature. An ISFET probe was then implanted<br/>into a prototype denture and characterised in AS. This study demonstrates the suitability of ISFET and gold<br/>electrode pH sensors for incorporation into implantable oral sensors.<br/>[1] G. Taylor and W. Borgnakke, “Periodontal disease: associations with diabetes, glycemic control and<br/>complications,” Oral Dis., vol. 14, no. 3, pp. 191–203, Apr. 2008.<br/>[2] E. Tékus, M. Kaj, E. Szabó, N. L. Szénási, I. Kerepesi, M. Figler, R. Gábriel, and M. Wilhelm,<br/>“Comparison of blood and saliva lactate level after maximum intensity exercise,” Acta Biol. Hung., vol. 63<br/>Suppl 1, pp. 89–98, 2012.<br/>[3] S. Naveen, M. L. Asha, G. Shubha, A. Bajoria, and A. Jose, “Salivary Flow Rate, pH and Buffering<br/>Capacity in Pregnant and Non Pregnant Women - A Comparative Study,” JMED Res., pp. 1–8, Feb. 2014.<br/>[4] A. F. Holthuis and F. S. Chebib, “Observations on temperature and temperature patterns of the gingiva. I.<br/>The effect of arch, region and health,” J. Periodontol., vol. 54, no. 10, pp. 624–628, Oct. 1983