To compare the effectiveness of the Quad Helix, an orthopaedic conventional appliance, in the correction of skeletal mandibular asymmetry, on frontal x-ray, in subjects treated before or after 7 years.

Introduction : 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.

Materials and methods : 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%.

Inclusion criteria:

• Unilateral Posterior Crossbite (at least one tooth) and skeletal mandibular asymmetry
• Treated by Quad Helix in the Orthodontic Department of the CHU Montpellier
• with frontal X-rays available at baseline and 12months later

Exclusion criteria:

• Incomplete File
• Inadequate quality of x-rays

Patients of Orthodontic Department of the CHU of Montpellier

NC