Nature, nurture, or noise? Fluctuating asymmetry in permanent dentitions depends on trait plasticity and...

Dental fluctuating asymmetry (FA) is thought to reflect developmental instability. It has varied relationships with other early life measures of stress. We examine whether this variation is due to FA reflecting sensitive windows of development or susceptibility to disruption, based on the traits considered.

Buccolingual and mesiodistal dimensions of all permanent teeth and molar intercuspal distances were measured from dental casts of 303 child participants of the Burlington Growth Study. Metric traits were aggregated into six discrete FA indices based on estimated age of trait development, trait susceptibility to environmental disturbances, or both. Early life biocultural factors were sourced from associated health history records and grouped into latent dimensions using factor analysis of mixed data. Using logistic regression, factors were then compared to all FA indices, separated by sex.

Model outcomes varied by FA index and sex. FA indices that consisted of molar intercuspal measurements were significantly associated with biocultural latent factors, but only among females. No predictive relationships were found among male-specific models.

Sensitive windows of development and differences in trait susceptibility to disruption are responsible for variation in dental FA of permanent teeth. Selecting traits with a high plastic component (such as molar intercuspal distances) rather than genetic component (crown dimensions) is critical to consider FA a metric of early life stress. Additional variability in dental FA, regardless of how it is measured, may be due to inherent "noise" in the developmental system.