3D analysis of maxillomandibular morphology in hyperdivergent and hypodivergent individuals: A cross-sectional study

Abstract

Introduction: The aim of this cross-sectional study was to investigate maxillomandibular morphology in hyperdivergent and hypodivergent individuals, using 3D surface models generated by cone-beam computed tomography (CBCT).

Methods: The sample consisted of 60 CBCTs (30 males, 30 females) patients aged 12-30 years, divided into two groups comprising hyperdivergent (≥35°) and hypodivergent (≤30°) individuals, according to the mandibular plane (MP) angle. Multiplanar reconstructions were used to mark the landmarks, and 3D surface models were created to evaluate structures of the maxillomandibular complex, including condyle, ramus, symphysis and palatal height. Intergroup comparisons were performed by independent t-test. Pearson's correlation test was used (P < .05) to evaluate the correlation of the MP angle with the angles and linear measurements of other structures.

Results: Significant differences were found between the groups regarding condylar width, ramus height, condylar plus ramus height, mandibular length, gonial angle, palatal plane angle and palatal-mandibular angle. No differences (P > .05) were found for the condylar height, symphysis inclination angle or palatal height. Correlations (P < .05) were found between the MP angle and structures of the maxillomandibular complex.

Conclusions: Hyperdivergent (MP ≥ 35°) and hypodivergent (MP ≤ 30°) individuals present different skeletal morphology regarding condylar width, ramus height, condylar plus ramus height, mandibular length, gonial angle, palatal plane angle and palatal-mandibular angle. There is a significant correlation between MP angle and morphological structures such as condyle, ramus, symphysis, palatal plane angle and palatal-mandibular angle.

Keywords: 3D models; computed tomography; maxillomandibular morphology; vertical pattern growth.

FIGURE 1

ITK-SNAP Software screen showing multiplanar cross-sections (axial, sagittal and coronal) and the 3D model. The three cross-sectional views and the 3D model were used as references to place the landmark.

FIGURE 2

3D surface model using ITK-SNAP. The landmarks were marked in different colours: light blue for the mandible ((A)—lateral view and (B)—posterior view), dark blue for the maxilla, and red for the cranial base, to avoid making mistakes during measurement (C).

FIGURE 3

Linear and angular measurements made by the 3D Slicer software using the Q3DC tool. Lateral views ((A) and (C)—Linear measurements, and (B)—Angular measurements) and superior view (C) show projections of 3D reference landmarks in all dimensions (vertical, transverse and anteroposterior).