Assessment of Mandibular Surface Changes During Growth and Development

Objectives: Growth of the mandible affects the outcome of orthodontic treatment in children. Traditionally, evaluation of mandibular growth uses two-dimensional (2D) cephalometric analyses. While still used by orthodontists today, these 2D analyses are fraught with errors in measurement associated with interpreting 2D projections of three-dimensional (3D) structures. Cone Beam Computer Tomography (CBCT) provides a means to study craniofacial structures in 3D. The current study identifies 3D topographical changes of mandible during the period of growth and development in orthodontic patients.
Methods: Ten subjects with serial CBCT images were selected from the Bolton-Brush collection. The age of the subjects ranged from 8 to 14 years-old. The maximum interval between two consecutive scans was 3 years. Mandibular growth is evaluated using serial pairs of CBCT images which are segmented, superimposed using regional voxel-based mutual information, and quantitatively evaluated in AmiraXImage^®. Intra- and inter-rater reliability for the technique was assessed.
Results: The findings of this study support the classic theories and elements of mandibular remodeling. Surface topography changes over time in these 10 subjects are reported as follows: 59% of surface remodeling at a threshold of 0.5mm, median remodeling of 0.6mm, 0.8mm ±0.6mm SD. Intra- and inter-rater ICC reliability for the superimpositions were 0.92 and 0.90, respectively.
Conclusions: The present study offers a reliable technique to superimpose serial CBCT data. The findings of this study support theories of bone remodeling reported in histological and radiographic studies of mandibular growth.