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Abstract
The effects of orthognathic surgery in three dimensions – 3D cephalometry
Aims Orthognathic surgery is an effective method for correcting significant skeletal and dentofacial
discrepancies. Surgery of craniofacial deformities is a complex task that requires careful
preoperative planning. While treatment must affect all three dimensions, many of the current tools
of diagnosis utilize only a two-dimensional representation of the patient. The development of a new
innovative technique like 3-dimensional cephalometry, based on multi-slice CT images could
improve the specification of the craniofacial skeleton, treatment planning and evaluation of the
result.
Is it possible to find significant landmark measurements that are useful during diagnosis? Is there a
constant relation between the diagnosis-significant landmarks of hard and soft tissue? How does
surgery influence these landmarks?
Methods From a single multi-slice CT data-set virtual lateral and frontal cephalograms are
computed and linked with both hard and soft tissue 3-D surface representations. To start the
analysis, the segmented hard and soft tissue representations are rendered in a virtual scene. This
innovative 3-D virtual scene approach allows accurate and reliable definition of Nasion and Sella,
the set-up of an anatomic Cartesian 3-D cephalometric reference system, definition of 3-D
cephalometric hard and soft tissue landmarks, the set-up of 3-D cephalometric planes and 3-D
cephalometric hard and soft tissue analysis.
Results Using the 3-D approach the definition of hard and soft tissue landmarks is accurate and
reliable. A general trend is found in the landmarks of hard and soft tissue. These landmarks are
meaningful in the diagnosis of orthognathic surgery. The influence of surgery on the landmarks is
dependent on the type of surgery.
Conclusion Three-dimensional cephalometry based on multi-slice CT images provides a better
insight into specification of the craniofacial skeleton and relation to soft tissue, treatment planning
and evaluation of the results.