Abstract
Objective/Aims:The aim of this study was to measure continuously the intraoral pH and temperature of healthy individuals to investigate their diurnal variations.Materials and Methods:Seventeen participants (mean age, 31±9 years) wore a custom-made intraoral appliance fitted with a pH probe and thermocouple for two sets of 24 h, while carrying out normal daily activities including sleep. The continuous changes in intraoral pH and temperature were captured using a sensor placed on the palatal aspect of the upper central incisors. The collected data were categorised into different status (awake and sleep) and periods (morning, afternoon, evening and night). Both quantitative and qualitative analyses were conducted.Results:The intraoral pH change was found to show a distinctive daily rhythm, showing a 12-h interval between maximum (7.73) and minimum (6.6) pH values. The maximum and minimum values were found to repeat after 24 h. The mean pH over 48 h (two sets of 24 h) was found to be 7.27 (±0.74). There was significant difference found in pH when subjects were awake and asleep and different periods during the day (P<0.001). The mean intraoral temperature was 33.99 °C (±4.9), with less distinctive daily rhythm compared with pH. There was a significant difference found in temperature depending on the time of the day, except between morning and afternoon (P=0.78).Conclusion:Our results showed that there is a distinctive daily, circadian-like pattern in intraoral pH variation over a 24-h period, which has been considered as one of the risk factors in sleep-related dental diseases.
Highlights
A key paper on circadian rhythms in saliva secretions was published by Dawes in 1972,1 which investigated the relationship over a 24-h period between saliva flow rate, oral temperature and the hours of a 24-h day
The intraoral pH varied depending been possible or practical to track salivary pH and flow rates long on the time of the day; the difference in pH when the participants term in locations especially where there is a risk of dental diseases were awake compared with when they were asleep was found to such as dental erosion
The mean intraoral pH and its variation during the 48 h are attempted by many researchers as a way of monitoring the saliva flow rate
Summary
A key paper on circadian rhythms in saliva secretions was published by Dawes in 1972,1 which investigated the relationship over a 24-h period between saliva flow rate, oral temperature and the hours (times) of a 24-h day. He found that stimulated and unstimulated saliva flow and oral temperature all showed significant circadian rhythms. In a follow-up study, Dawes[2] reported that secretion levels of salivary substances were found to follow a circadian rhythm. Adequate salivary flow and saliva content were directly related to health status as it plays an important role for effective nutrition, maintenance of body functions and especially oral homoeostasis.[3,4,5,6] Recent studies have reported that salivary glands, like other human organs such as the kidneys, contain a circadian clock.[3,4] Zheng et al.[3] confirmed that the circadian clock of salivary glands is a peripheral clock, which regulates the type, amount and content of saliva as well as the fluid secretion
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