THE MANDIBULAR SHAPE IN OPEN BITE EARLY TREATMENT RELAPSE: A GEOMETRIC MORPHOMETRIC ANALYSIS

Background: To evaluate the mandibular shape differences between a group of success and a group of failure Anterior Open Bite malocclusion early orthodontic treatment in growing subjects, in order to identify mandibular features of relapse. Methods: 23 patients (7 males, 16 females, 9.3 years ± 1,5 years) were enrolled from the Department of Orthodontics at the University of XXXXXXX. Inclusion criteria were: white ancestry, OVB<0 mm, mixed dentition phase, cervical skeletal maturation CS1-CS2, no previous orthodontic treatment, no congenital diseases. Pre-treatment (T1) lateral cephalograms were acquired. Each patient underwent early orthodontic treatment with Rapid Maxillary Expander (RME) and Bite Block (BB) or Quad-Helix Crib (QHC) until open bite correction. Radiographic records were recollected at T2 (permanent dentition, skeletal cervical maturation CS3-CS4). Mean interval time T2-T1 was 4.2 years. According to treatment stability, a Relapse Group (RG, 11 subjects) and a Success Group (SG, 12 subjects) were identified. Mandibular cephalometric measurements were analysed and mandibular Geometric Morphometric analysis (GMM) was applied. Intergroup statistically significant differences were found using student’s t-tests. Procrustes analysis and principal component analysis (PCA) were performed for the GMM. Results: At T1 no statistically significant differences were found between RG and SG, however higher values of antegonial notch depth were found in RG. T2-T1 comparison showed in RG statistically significant increases in Co-Gn (p=0.04), NGo^GoMe angle (p=0.01) and antegonial notch depth (p=0,04). PC1 confirmed the increase in the antegonial notch depth in RG when compared to SG at T2. Conclusions: The increased mandibular length, the increased inferior gonial angle and the increased antegonial notch depth can be considered features of relapse in early orthodontic treatment in open bite growing subjects.