Velopharyngeal and Glossopharyngeal Volume Changes after Implant Anchored Maxillary Expansion

Purpose: Evaluation of the changes of the segmented 3D model of the pharyngeal airway volume and surface area after using conventional and hybrid Hyrax (with micro implant) for maxillary expansion using MIMICS software.
Materials and methods: Sample size: 20 male patients with constricted maxilla dedicated for maxillary expansion as a part of orthodontic treatment plan. For each patient, written acceptance consent was taken to participate in the study. Selection criteria: - Age 12-14 years. - Absence of any: previous orthodontic intervention, breathing disorder, deformities that may affects the craniofacial structures. - Constricted maxilla indicated for Hyrax Rapid Palatal Expansion (RPX). The sample was divided into two groups: The first group (10 patients) was treated with conventional Hyrax appliance supported on first permanent molars bilaterally (dental anchorage). The second group (10 patients) treated with hybrid Hyrax supported on first permanent molar and first premolar bilaterally, this appliance incorporating two eyelets for additional skeletal anchorage with two micro-implants. For each patient enrolled in this study a full skull CT x ray was done just before the insertion of the Hyrax appliance and after 10 days of rapid palatal expansion at a constant rate for all patients. The full skull CT was processed via MIMICS software for segmentation, 3D modeling and measurements of the pharyngeal airway volume and surface area from the level of the hard palate to the lower border of the hyoid bone.
Results: -For both conventional and Hybrid Hyrax, Rapid Palatal Expansion resulted in statistically significant increase in the pharyngeal airway volume and surface area (1.87cm3,
2.52cm3, 1,68cm2 and 2.48cm2) respectively. -Greater increase in the pharyngeal airway volume and surface area in the second group due to incorporation of the micro-implants but the statistical differences between both groups was found to be non-significant.
Conclusions Both conventional and hybrid Hyrax produced significant increase in pharyngeal airway volume and surface area, this effect can be augmented by incorporating skeletal support (micro implant) in the Hyrax appliance.