Continuous 4D Shape Analysis of Mandibular Changes
Objectives: To present an innovative technology to model biological shape evolution that continuously quantifies changes following Orthognathic Surgery and mandibular growth.
Methods: We use a validated methodology based in spatio-temporal shape regression to generate a mandibular change model. Cross-sectional three-dimensional shape analysis can quantify shape changes but it does not model dynamic processes such as growth, surgery and post-surgical adaptations. This methodology estimates a single deformation that best represent the evolution of a collection of structures collected over time. The deformation computed is topology-preserving and smooth to ensure the modeling of biologically feasible growth.
Results: Four CBCT scans were collected between the initial clinical visit and the 6 year post-surgical follow up (16-22 years old), for a patient that had severe open bite and underwent surgical maxillary impaction. Note that even though no surgery was performed in the mandible, bone re-shaping was progressive. The baseline CBCT showed radiographic signs of flattening on both condyles before surgery that progressed during post-surgery orthodontics and in the follow up visits. The computed model of bony changes showed the continuous progression of mandibular shape changes, with bone remodeling between scans. The model shows the expected mandibular changes and the condylar flattening detected in our cross-sectional analysis, but also displayed a widening of the mandibular arch and a mild bilateral condylar torque happening over time.
Conclusions: Our initial shape analysis provided localized information of mandibular shape changes, but the continuous evolution model provided further details about the dynamic processes associated with treatment and long-term changes. The proposed spatio-temporal shape model computes continuous mandibular shape information that describes and quantifies local and global shape changes across the series of observed scans. This novel continuous shape modeling may potentially lead to improved understanding of development, growth trajectory, degeneration or recovery in a variety of craniofacial complex problems.