Is the Quad Helix More Efficient to Correct Mandibular Asymmetry Before Age 7? A Retrospective Comparative Study

Unilateral posterior crossbite (UPCB), often from dysfunctional and para-functional causes, leads to positional mandibular asymmetries that can develop at a very young age into skeletal mandibular deviation; hence the interest of early maxillary expansion. The purpose of this retrospective study was to compare the impact of maxillary expansion by Quad Helix (QH) on mandibular skeletal asymmetry correction before and after 7 years of age.

All children with UPCB and skeletal mandibular asymmetry, who were treated by QH in the orthodontic department between February 2017 and August 2018 and who have done a radiography file at baseline (T0) and 12 months later (T1) have been included. The patients were divided into two groups according to age: under 7 years of age (early group G1) with QH adjusted on second primary molars and over up to 13 years old (late group G2) with QH adjusted on first permanent molars. The differences between the right and left sides of the mandible in corpus length L (main eligibility criterion) and ramus height H (secondary criterion) were compared between groups. X² test, Fisher's exact test and Wilcoxon rank-sum tests were used for baseline comparisons. A multifactorial analysis allowing adjustment on possible confounding factors was used with R software at a significance level of 5%.