Mimics 14

MRI was performed at the Department of Diagnostic Radiology of The University of Hong Kong with a clinical 3.0T MRI system (Achieva 3.0T TX, Philips healthcare, Netherlands). The images of the head were acquired on the sagittal plane with a 3D T1 sequence (3D THRIVE sequence), 1 mm × 1 mm × 1 mm voxel size, 32 s scan time.
During scanning, awake patients were in the supine position and were asked to breathe normally through their nose, not to move their head, and to refrain from swallowing.
The MRI images were measured using image-processing software (Mimics 14.1, Materialise, Leuven, Belgium). Before measurement, images were reoriented along the sagittal, axial, and coronal planes to standardise the head position. Measurements of the upper airway included depth, width and area at nasopharynx (NA), retropalatal oropharynx (RP), retroglossal oropharynx (RG), and hypopharnx (HP) (Figure 3).

CBCT data sets were acquired with a DCT Pro CBCT (Vatech, Co., Ltd., Hwasung, Korea) using the following scanning parameters: 90 kVp, 24 s, 4 mA, voxel size 0.4 mm and field of view 20 × 19 cm. The images covered the area from the upper orbits rim to the inferior border of the mandibular body. The gross data and slices were imported and used to reconstruct 3D models with an interactive image system (Materialise’s interactive medical image control system, Mimics, 14.0; Materialise, Leuven, Belgium). The upper and lower limits of the condyle were defined according to Tecco, S., et al. (Fig. 2) [13 (link)]. Volumetric (mm³) and surface size measurements (mm²) were made for condyles on two sides at the T0 and T2 stages in the USSRO and BSSRO groups using the Mimics™ automatic function.Fig. 2

The superior, inferior and lateral limits of the 3D constructed models of mandibular condyles

The maxillae were collected and fixed in 10% neutral buffered formalin (NBF) overnight. The structure of alveolar bone was evaluated by using the SkyScan 1172 μCT scanner (SkyScan) with the following parameters: 49 kV, 200 μA, 0.7 mm aluminum filter, and 11 μm resolution. μCT data were analyzed between the first and second molar regions on the buccal and lingual sides after drawing the region of interest (ROI) using CTAn (SkyScan) and Mimics 14.0 (Materialise).

Procedures for the preparation of mandible samples and micro-CT were as previously described [13 (link)]. Briefly, 3-, 6-, and 9-month-old mice were euthanized using compressed 5% CO₂ gas and their mandibles and femurs were removed and fixed overnight with 4% buffer-saturated paraformaldehyde. Bones were scanned using a Scanco80 (μ80) system (Scanco Medical AG, Bassersdorf, Switzerland). The instrumental isotropic resolution was 10 μm and the iso-surface was reconstructed using two-dimensional raw data using MicroView analysis software (GE Healthcare, Little Chalfont, UK). The image analysis method was based on Hounsfield units (2800 units) and region-grow algorithms to segment image data defining separate anatomical structures. Images were reconstructed with Mimics® 14.0 (Materialise, Leuven, Belgium) software using a global threshold of 1400 Hounsfield units.

Before surgery, all of the patients were received pre-surgicalorthodontictreatment. Alignment and coordination of the maxilla-mandibular dental arch width were performed to ascertain that the Me point could be adjusted to a precise position. CBCT images of patients with pre-surgical orthodontic treatment were acquired using the DCT Pro CBCT device (Vatech Co., Ltd., Hwasung, Korea), while 3D reconstruction was performed using the Mimics^™ program (Materialise’s interactive medical image control system, Mimics, 14.0; Materialise, Leuven, Belgium). Virtual BSSRO was then performed on the 3D craniofacial models. The distal segments were separated from the proximal segment on both sides of the mandible, and the proximal segment was rotated and shifted backwards to achieve normal jaw relationship and midline alignment. Maxillary surgery (Lefort I) was additionally performed if an inclination of the occlusal plane was noted. After correction of the Me point, a real virtual mirroring plane (a sagittal plane passing through the facial midline and corrected Me point) for residual asymmetry measurement was created. The elongation side of the hemi-mandible was mirrored to create a mirrored model. Residual asymmetry was defined as the superimposition and boolean calculation of mirrored elongation side on the normal side (Fig 1).