Do biofilms take a break at night?

The oral cavity creates more biofilm during the day than at night, according to a study in Acta Odontologica Scandinavica (December 2012, Vol. 70:6, pp. 441-447).

Most previous studies of accumulation and composition of dental biofilms in vivo do not differentiate between biofilms formed during the day and at night, according to the study authors, from Aarhus University.

To determine whether oral bacteria have a natural circadian rhythm, they collected in situ biofilm from healthy individuals for 12 hours during the day and 12 hours at night. The biofilm samples were then analyzed using confocal laser scanning microscopy.

The researchers found a statistically significant difference between both the total number of bacteria and the biovolume in the two 12-hour groups (p = 0.012), with the highest accumulation of bacteria during the daytime. Their analysis also indicated a higher proportion of streptococci in biofilms grown during the day than at night.

"The data provide firm evidence that initial biofilm formation decreases during the night, which may reflect differences in the availability of salivary nutrients," the researchers concluded.

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