The aim was to evaluate the association between circadian rhythm and the risk of caries in adolescents, as well as their dietary and toothbrushing habits.


A group of 196 adolescents (15 and 16 years old) were divided into two equal groups based on caries risk (case = high risk; and control = low risk). Before their dental examinations, they were asked to complete a questionnaire. The questionnaire included questions on circadian rhythm, dietary and oral self-care habits, and demographic variables. The participants were divided into three circadian types: evening types who are alert in the evening and tired in the morning; morning types who are the opposite; and neutral types who are neither particularly alert in the evening nor extremely tired in the morning.


The most common sleep-cycle group type was neutral (50%). After this came evening types (37%) and finally morning types (13%). Morning and neutral types reported more frequently than evening types that they had breakfast every morning and brushed their teeth twice a day. More evening types were categorized as at high risk of caries. Circadian rhythm, breakfast habits and toothbrushing frequency were associated with a high risk of caries. The predicted probability of being at high risk of caries was almost four times higher for evening types than for morning types (OR 3.8; 95% CI 1.3–10.9).


Adolescents who belonged to the evening circadian rhythm group brushed their teeth more seldom, ate breakfast less regularly and had a higher risk of caries than morning types. A patient’s circadian rhythm should be considered when planning oral health education for adolescents with a high risk of caries.

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