Reassessment of fluctuating dental asymmetry in Down syndrome

Marcos Matabuena Rodríguez,Pedro Diz Dios,Carmen Cadarso-Suárez,Márcio Diniz-Freitas,Mercedes Outumuro Rial,Maria Teresa Abeleira Pazos,Jacobo Limeres Posse

doi:10.1038/s41598-017-16798-0

Marcos Matabuena Rodríguez, Pedro Diz Dios + Show 5 more

Open Access

https://doi.org/10.1038/s41598-017-16798-0

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Abstract

Fluctuating dental asymmetry (FDA) is a tool to measure developmental stability that could be increased in gonosomal aneuploidies. The aim of this study was to quantify FDA in individuals with Down syndrome (DS). The study group comprised 40 individuals with DS, and a control group matched for age and sex was created. The target teeth were the maxillary central incisors (11,21), maxillary lateral incisors (12,22), maxillary canines (13,23), and maxillary first molars (16,26). Dental morphometric variables measured on CBCT images included tooth length, crown height, root length, mesio-distal diameter, crown-to-root ratio, vestibular-palatine diameter, mid mesio-distal diameter, mid buccal-palatal diameter, maximum buccal-palatal diameter, and cervical circumference. The FA2 fluctuating asymmetry index (Palmer and Strobeck, 1986) was applied. Some discrepancies in crown-to-root ratios and root length asymmetry were significantly lower in the DS individuals than in controls. Combining the crown-to-root ratio of tooth 11 versus 21, tooth 12 versus 22, and tooth 13 versus 23, we developed a predictive model with a discriminatory power between DS and controls of 0.983. Some dental morphometric variables may actually be more stable in DS individuals than in the general population. This offers a new perspective on the relationship between canalization, fluctuating asymmetry, and aneuploidy.

Highlights

The concept of canalization refers to a phenomenon whereby the development of phenotypic traits is buffered against environmental influences, so that such traits produce a highly predictable genetically determined endpoint[1]
With the exception of the crown-to-root ratio of teeth 11, 21, and 16, the root length of tooth 22, and the crown height of tooth 26, all values were significantly lower in the individuals with Down syndrome (DS)
Microdontia of the permanent teeth is considered a phenotypic characteristic of DS28, and for comparison with non-syndromic control groups, asymmetry of dental morphometric variables in individuals with DS should not be evaluated in terms of absolute right-left differences

Summary

Introduction

The concept of canalization refers to a phenomenon whereby the development of phenotypic traits is buffered against environmental influences, so that such traits produce a highly predictable genetically determined endpoint[1]. The canalization capacity of an organism is called developmental stability[2] and its measurement is based on small variations of antimeric traits at random with respect to side (right-left). This biological asymmetry of morphological traits is called fluctuating asymmetry[3]. The main drawback of that study was that asymmetry of the dental morphometric variables was measured as the absolute value of the difference between right and left, while the most useful descriptor of fluctuating asymmetry is variance[3,24]. The aim of the present study has been to reassess fluctuant dental asymmetry in a series of individuals with DS, evaluated objectively without taking into account the absolute size of the teeth and, without the effect of scale

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