Janjić K, Agis H. Chronodentistry: the role & potential of molecular clocks in oral medicine. BMC Oral Health. 2019 Feb 13;19(1):32. doi: 10.1186/s12903-019-0720-x.
What is the circadian rhythm?
Molecular clocks help organisms to adapt important biological functions to periodically changing conditions in the environment. Depending on the cycle length of respective biological rhythms, different types of molecular clocks have been defined:
- the circadian clock (24 h periods); adapting to daily changes,
- the circalunar clock (29.5 d periods); adapting to moon phases and
- the circannual clock (365 d periods); adapting to seasonal changes
The most fundamental one, the circadian rhythm, is known to act as a key regulator in processes of health and disease in different organs.
Why is the circadian rhythm (CR) important to us?
First attempts to discover the circadian clock in dental tissues focused on tooth development and only recently evidence was raised that also oral tissues in adults contain a peripheral clock.
When the central circadian clock in the brain receives light or dark impulses, it transmits them to peripheral clocks such as those in oral tissues in a 24 h rhythm.
Certain types of lifestyle which deviate strongly from this daily rhythmicity can cause poor coordination of peripheral clocks, ultimately leading to a dysfunctional clock.
- For example, shift work is associated with an increased incidence of oral health problems
- Circadian production of melatonin, a sleep-related hormone, seems to be correlated with tooth development.
- A functional clock is thus relevant for oral health.
A deeper look into chronodentistry
Chronodentistry opens great potentials for advances in dental applications. This review summarised current knowledge on the circadian clock in oral tissues with the aim to raise awareness for findings that are relevant for the main fields of dental practice.
- Dental pulp, periodontal tissues, oral mucosa, enamel, dentine and mandibular bone show clear evidence for the presence of peripheral clocks
- Saliva production, pH levels, and microbial activity have also shown to have circadian variations in the oral cavity
- A dysfunctional clock mechanism has been attributed to be involved in the development of oral cancer and juvenile skeletal mandibular hypoplasia
Application of molecular clocks in different fields of dentistry
- Periodontology: CRs could be assessed for their ability to stimulate oral soft tissue healing and periodontal regeneration
- Endodontics: Pain sensation and analgesic treatment in oral regions correlates with CRs – further studies can help improve patient comfort
- Restorative: regenerative potential for dental hard tissues through the exploitation of the influence of CRs in enamel and dentine formation
- Orthodontics: the effects of orthodontic forces in bone remodelling affected by CRs – can be suggested to adjust periods of wearing removable orthodontic appliances in resting phase, supporting a stronger effect and shortening wearing periods for patients.
Application of molecular clocks in oral medicine
The paper further explored the possibility of optimising the timing of drug administration to circadian oscillations to increase its effectiveness and efficiency. The authors found a review on chronopharmacology from 2016 which reported that a precise timing of drug use could also relieve patient’s metabolism, reduce costs and required appointments at the dentist’s, altogether improving daily routines.
Conclusion
The field of chronodentistry has been found to be promising and could revolutionise dentistry with new or refined therapeutic approaches
Research Summary Written By: Areej Raza, University of Manchester, BDS4