[What are the factors associated with mandibular asymmetries? A case-control study]

The treatment of mandibular asymmetry often requires a late surgical orthodontic protocol that certainly allows an improvement but no complete correction. Ideal would be to control the etiological factors which are still controversial. The aim of the study is to identify per and postnatal factors associated with the development of mandibular asymmetry. This case-control study was performed with a cohort of 100 individuals divided in two subgroups. A subgroup of 50 subjects with mandibular asymmetry and another subgroup of 50 subjects without mandibular asymmetry. The subjects included in the study had to be from 6 to 16 years old, have a complete orthodontic file and no congenital syndrom or pathology. The following factors have been assessed: gender, mode and date of birth, dental trauma, visual disorders, ENT problems and parafunctions. An inter-group comparison had been performed by using statistical tests (Chisquare test, Fisher test and odds ratios calculation). The associated factors with mandibular asymmetry are male gender, oral ventilation, short-term vaginal nasalization, dental trauma and visual disorders. Asthma (symmetrical character of the anomaly ?), prematurity and caesarean section (by absence of trauma at delivery ?) would not be considered as associated factors. This case-control study is a first-line study that allows the identification of factors that may be associated with mandibular asymmetry. Ideally, a larger-scale prospective cohort study to increase the pertinence would clarify the risk factors for the development of mandibular asymmetry.