The Relationship between Sleep, Chronotype, and Dental Caries-A Narrative Review

This article provides an overview of how sleep and circadian rhythm disturbances mutually influence the occurrence of dental caries and how it is possible to reduce the risk of circadian rhythm disturbances, sleep, and associated adverse effects. Dental caries is a global problem worldwide that contributes to sociological limitations. Numerous factors influence the occurrence of dental caries, from socioeconomic factors to cariogenic bacteria, dietary habits, and oral hygiene. However, sleep disorders and circadian rhythm disturbances represent a new approach in the fight against the increasing prevalence of dental caries worldwide. Bacteria in the oral cavity and the oral microbiome are mainly responsible for the development of caries, and saliva plays an important role in their regulation. The circadian rhythm regulates numerous physiological functions, including sleep and saliva production. Disturbances in sleep and circadian rhythms affect saliva production, which impacts the development of dental caries, as saliva is necessary for regulating and maintaining oral health, especially for controlling oral infections. A person's preference for a particular time of day depends on the circadian rhythm called chronotype. Individuals with an evening chronotype have a less healthy lifestyle that can lead to a higher caries risk than individuals with a morning chronotype. Because circadian rhythms are critical to maintaining sleep homeostasis and oral health, sleep disturbances can disrupt circadian rhythms and lead to a vicious cycle.

Is chronotype profile a risk indicator for caries in children and adolescents in sub-urban Nigeria?

OBJECTIVES

To determine the association between chronotype and the prevalence of caries among in-school pupils aged 6- to 16-year-old residing in a sub-urban area in Nigeria. We hypothesize that in-school pupils who are evening chronotypes will have significantly higher prevalence of caries than those who are intermediate or morning chronotypes.

METHODS

This secondary analysis of a dataset collected in 2019 from 1502 children aged 6- to 16-year-old attending private and public primary and secondary schools in Ife Central Local Government Area, Nigeria. The dependent variable was caries prevalence. The explanatory variable was participants' chronotype profile (morning, intermediate, and evening). The confounding variables were caries risk factors (socio-economic status, age at last birthday, sex, use of fluoridated toothpaste, frequency of consumption of refined carbohydrates, and oral hygiene status). Poisson regression analysis was conducted.

RESULTS

Data of 1001 (66.6%) students were retrieved. Of these, 59 (5.9%) had caries, 42 (4.2%) were evening type, 526 (52.5%) were intermediate type, and 433 (43.3%) were morning type. There was no significant association between chronotype and the prevalence of caries though children who were intermediate type (APR = 0.83; 95%CI: 0.41-1.66) and morning type (APR = 0.57; 95% CI: 0.27-1.18) were less likely to have caries than were those who were evening type.

CONCLUSION

The children and adolescents' chronotype was not a significant risk indicator for caries in the study population.

Do chronotype differences and night eating syndrome affect dental health?

OBJECTIVE

Our aim in this study was to examine the effect of chronotype differences and night eating syndrome on dental health parameters such as the decay-missing-filled teeth (DMFT) index, the severity of the periodontal disease and the number of endodontically treated teeth in patients admitted to the dental clinic.

METHODS

The participants, 210 patients, filled out a package of psychological tools, including the Morningness-Eveningness Questionnaire (MEQ), the Night Eating Questionnaire (NEQ) and the Insomnia Severity Index (ISI). Afterwards, the DMFT index scores, the severity of the periodontal disease and the number of endodontically treated teeth of patients were recorded simultaneously with a routine dental examination.

RESULTS

Findings show that the ISI and NEQ scores were significantly higher in the evening-type individuals (E-types) than in the morning-type individuals, and there was no significant difference between the chronotypes in terms of the number of endodontically treated teeth and the DMFT scores. In ordinal regression analyses, not brushing teeth (OR 7.94, CI 6.40-9.85), increased number of decayed teeth (OR 1.16, CI 1.13-1.19) and decreased MEQ scores (OR 0.95, CI 0.94-0.95) were statistically significant predictors for periodontal disease.

CONCLUSION

Although there was no correlation between chronotype differences and the DMFT index, and the number of endodontically treated teeth, E-types had a higher risk of periodontal disease severity.

Late bedtime and dental caries incidence in Kuwaiti children: A longitudinal multilevel analysis

OBJECTIVE

Inadequate sleep contributes to several adverse systemic health outcomes due to hormonal and metabolic disorders. The purpose of this study was to determine the effect of bedtime on the development of dental caries and the relationship with salivary ghrelin and leptin in a prospective cohort study of Kuwaiti children.

METHODS

Data were collected from 5456 10-year-old children in 2012 and repeated in 2014. We selected children from 138 middle schools representing the six governorates of Kuwait. We derived data from oral examinations, self-reported sleep interviews, body and weight measurements, and chemical analysis of whole saliva samples. Leptin and ghrelin were determined by salivary assay in a subset of 744. Two separate analyses were performed. a) Using the entire longitudinal data set (n = 5456), multilevel random intercept analysis was conducted to assess the relationship between reported bedtime and dental caries. b) Using data from a subset of the original sample (n = 744), multiple linear regression analysis was conducted to determine the relationship between dental caries and salivary ghrelin and leptin. The outcome variable was the development of dental caries in children. The independent explanatory variables and confounders were bedtime, sleep duration, salivary ghrelin and leptin; confounders assessed were gingivitis, sex, age and governorate (school location).

RESULTS

With every additional hour past 8 pm for bedtime, there was a 20% increase in dental caries incidence over two years (B = 0.2, P = .01), adjusting for age, gender, gingivitis and governorate. There was a significant difference in the magnitude of dental caries between the six governorates of Kuwait. Lower levels of salivary leptin and higher levels of salivary ghrelin were associated with increased dental caries, and sleep duration was an effect modifier that negatively affected the relationship between leptin and dental caries (B = -0.09, P < .05) and positively affects the relationship between ghrelin and dental caries (B = 0.07, P < .05). Additionally, there was a significant clustering effect within schools in this cohort.

CONCLUSION

In a cohort study of Kuwaiti children, late bedtime was associated with increased dental caries incidence. Additionally, dental caries experience increased with higher levels of salivary ghrelin and lower levels of salivary leptin, and sleep duration mediates the relationship between these two biomarkers and dental caries.

The Risk of Night Shift Workers to the Glucose Blood Levels, Saliva, and Dental Caries

OBJECTIVE

This study aimed to provide the correlation of circadian rhythms of night shift workers with blood glucose levels, saliva, and dental caries.

MATERIALS AND METHODS

This study was conducted on night shift and nonshift workers to measure fasting blood glucose (FBG), 2-hour postprandial blood glucose (2-PP BG), saliva flow rate, pH saliva, and caries with the decay-missing-filled total (DMF-T) index. Data analysis was done using independent t-test and correlation test with Pearson correlation.

RESULTS

There were significant differences in night shift and nonshift workers in FBG (p = 0.000), 2-PP BG (p = 0.000), flow rate saliva (p = 0.000), and DMF-T index (p = 0.001). Correlation test showed positive correlation between FBG and pH saliva (r = 0.42, p = 0.029) and DMF-T index (r = 0.521, p = 0.005) of night shift workers. The 2-PP BG also showed positive correlation with pH saliva (r = 0.493, p = 0.009) and DMF-T index (r = 0.743, p = 0.000). The DMF-T index showed negative correlation with flow rate saliva (r = -0.398, p = 0.04). In the nonshift workers, correlation test showed a correlation between FBG and DMF-T index (r = 0.384, p = 0.048). The DMF-T index showed correlation with flow rate saliva (r = 0.6, p = 0.001).

CONCLUSION

There is a circadian rhythm correlation between night shift workers to blood glucose levels, flow rate saliva, pH saliva, and dental caries.

Daily life habits associated with eveningness lead to a higher prevalence of dental caries in children

Background/purpose

Circadian rhythm is an endogenous daily variation observed in most physiological functions including salivary secretion. Irregular lifestyle causes many diseases such as obesity and sleep disorders. The aim of this study is to examine the effects of the timings of sleep and meal on the prevalence of dental caries.

Materials and methods

Study was conducted at university hospital in Japan. We asked 230 children (1–16 years old) to record the following life habits for 8 days: waking time, bedtime, mealtimes, snacking frequency, and tooth brushing frequency. We analyzed sleep habits from all data and compared dental caries and life habits using data from subjects with primary (2–7 years old) or permanent (11–16 years old) dentition period.

Results

The number of dental caries assessed using the decay or filled teeth (dft) index correlated with bedtime, supper time, regularity of supper time, and snacking frequency in subjects with primary dentition. Multiple regression analysis revealed that bedtime and snacking frequency were mutually independent risk factors for dental caries. No correlations were found between the prevalence of dental caries and other measurement items. The number of caries correlated with the regularity of supper time and age in subjects with permanent dentition.

Conclusion

Children with daily life habits associated with eveningness have a higher prevalence of dental caries.

Association among chronotype, dietary behaviours, and caries experience in Brazilian adolescents: Is there a behavioural pattern?

BACKGROUND

Dental caries (DC) remains a public health issue. Chronotype, diet, and oral hygiene may influence its development.

OBJECTIVE

To investigate the association of chronotype, diet, oral hygiene, and DC among 12-year-olds.

METHODS

A cross-sectional study with 245 adolescents was conducted in public and private schools in southeast Brazil. Sociodemographics, dietary and oral hygiene habits were collected through a self-reported questionnaire. Chronotype was assessed using the Portuguese version of the Puberty and Phase Preference Scale (PPPS). Subjects were examined for DC (WHO criteria). Bivariate and multivariate analyses were performed (P < 0.05).

RESULTS

DC was present in 42.0% of the sample. In the bivariate analysis, a higher DMFT was associated with living in rural areas (P = 0.006), parents'/caregivers' lower schooling (P = 0.008), and a not daily intake of vegetables (P = 0.033). Chronotype was not associated with DMFT scores. The Poisson regression model showed that adolescents who did not have breakfast regularly (PR = 1.55; 95% CI = 1.17-2.08; P = 0.003), lived in rural areas (PR = 2.20; 95% CI = 1.59-3.04; P < 0.001) and did not consume vegetables daily (PR = 1.55; 95% CI = 1.11-2.17; P = 0.009) were more likely to present a higher DMFT.

CONCLUSIONS

DC is associated to living in rural areas and dietary habits, such as not having breakfast regularly and lack of daily intake of vegetables.

Prevalence of sleep bruxism and awake bruxism in different chronotype profiles: Hypothesis of an association

Sleep (SB) and awake bruxism (AB) recognize a multifactorial etiology and have a relationship with several psychological factors. Psychological disorders have recently been associated also with the chronotype, which is the propensity for an individual to be especially active at a particular time during a 24-h period. Based on the chronotype, the two extreme profiles are morningness and eveningness individuals. Due to the relationship that both the chronotype and bruxism have with psychological factors and the fact that performing tasks not compatible with chronotype can trigger stress, this review presents the hypothesis that the prevalence of SB and AB can differ with the various chronotype profiles. New perspectives for the study of bruxism etiology may emerge from investigations on the topic.