Continuous Measurement of Intraoral pH and Temperature

Abstract

Dental erosion has been recognised as a major issue in dentistry - with epidemiological studies reporting an increasing prevalence of this condition. Salivary functions are the most significant factors in dental erosion; salivary pH in particular has an important role in the pathogenesis of these lesions and other problematic oral conditions. It has remained difficult to monitor salivary pH changes intraorally over time as most measurements are either done in vitro or in situ by saliva sampling. This limits the ability to fully understand the aetiology and changes in salivary pH. Intraoral temperature has a close relationship with pH but, to date, there has been no study that has reported simultaneous measurement of intraoral pH and intraoral temperature over a 24-hour period.

This thesis begins by reviewing the literature on tooth wear, especially dental erosion. By identifying the causal factors, saliva, in particular the salivary (intraoral) pH, plays the most significant role in the development of dental erosion. It was found that there is a large amount of research on the association of acidic food and drink consumption and the development of erosion, however, several risk groups such as individuals with xerostomia (dry mouth), and sleep and respiratory disorders, have not been well-studied. It was also found that there are few studies that have investigated normative intraoral pH variations over extended periods especially during sleep due to the limitation of intraoral pH measuring devices used. Intraoral pH and temperature are related, however, there is also a limited study available on the measurement of intraoral temperature for extended period. Therefore, another literature review was conducted to investigate the paucity in the research to monitor the intraoral pH over an extended period. The literature review clearly identified the need for a novel device to be developed that measures simultaneously both intraoral pH and temperature.

A novel device to measure intraoral pH and temperature was developed and validated. It was found that intraoral pH and temperature can be measured successfully – continuously and simultaneously. Based on the studies conducted using this device, it was found that there is a decrease in intraoral pH during sleep and a noticeable difference in the pattern of variation of pH and temperature between day (7.3 ± 0.4; 33.9 oC ± 0.9) and night (6.6 ± 0.4; 35.9 oC ± 0.5). Moreover, mouth breathing during sleep was found to be related to a decrease in intraoral pH compared with normal breathing during sleep, and this has been reported as a causal factor for dental diseases. The mean intraoral pH during sleep was 7.0 (± 0.5) and during sleep with mouth breathing was found to be 6.6 (± 0.5), which was found to be statistically significant (p < 0.05). No statistical significance was found in intraoral temperature between sleep with and without mouth breathing (p = 0.38). It was further found that there is a strong circadian rhythmic pattern in intraoral pH variation over a day. Lastly, from a pilot study conducted, it was found that there is an interarch difference in intraoral pH and a noticeable difference in the pattern of variation of pH and temperature between maxilla (7.32 ± 0.52; 33.12 oC ± 5.51) and mandible (7.07 ± 0.26; 36.18 oC ± 0.96) when measured over a 24 hour period.

The research described in this thesis showed that the development of a novel device to measure intraoral pH and temperature continuously over extended period can provide invaluable normative data for healthy individuals and help provide a better understanding of changes in intraoral pH related to the circadian rhythm of saliva in particular for investigating a relationship between dry mouth, mouth breathing and dental erosion, and other oral conditions related to intraoral pH, such as dental caries.