Methods: We designed and constructed a custom made appliance fitted with a pH probe (ResTech Corp, USA) and a thermocouple (Lascar Electronics Inc., USA). Five healthy subjects wore the appliance for 2 non-consecutive days, 24 hours on each day and pH and temperature were measured. One subject wore the appliance for an additional 4 days. For 3 nights out of the 6, she had her nose blocked with cotton rolls at night to simulate mouth-breathing conditions during sleep.
Results: There was a significant difference in the pattern of variation of pH between day and night. For all days of the study, the average pH of 7.38 was maintained while the subject was awake except after consumption of acidic food or drinks. However, the intraoral pH decreased slowly over the hours of sleep. When sleeping with forced mouth breathing, intraoral pH showed a greater fall over a longer period of time and remained below the pH 5.5, four times longer. The average intraoral temperature was 34.7 °C, which showed minor fluctuation during 24 hours except while talking and exercising. Mouth breathing did not affect the intraoral temperature significantly.
Conclusions: The intraoral pH and temperature measurement system we present is reliable, easy to construct and may serve as a future research and diagnostic tool in a number of applications. The evidence from this study suggests that there is a strong relationship between the intraoral pH and mouth breathing.
Implications: Intraoral pH measurement, especially during sleep is able to provide valuable information on saliva dysfunctions and erosion of teeth.