Assessing treatment outcomes is important when documenting treatment changes and research. The approach to lateral cephalometric superimposition used by the American Board of Orthodontics involves cranial base registration on the outline of the sella turcica and the best fit of the anterior cranial base bony structures, using the lingual curvature of the palate with the best fit on the maxillary bony structures, and registration on the internal cortical outline of the symphysis with the best fit on the mandibular canal for superimposition of the maxilla and mandible, respectively. Clinicians who have performed this type of cephalometric superimposition are aware that it is a challenging process owing to issues related to image fidelity, landmark selection and identification. Because the method is limited to superimposition of lateral cephalograms, the information is only from the sagittal plane.
The introduction of CBCT allows clinicians to perform superimpositions in three dimensions and has eliminated some of the errors that occur with traditional lateral cephalometric superimposition. Recently, a method for superimposition of CBCT images that does not first require segmentation or landmark selection was developed that is accurate, fast and automatic. Because this method eliminates the need for segmentation and selecting landmarks, the errors associated with these steps are eliminated, thereby reducing the overall cumulative errors. Common weaknesses of many outcomes studies are image fidelity and method errors in the superimposition process, leading to confounding and often conflicting results. The application of CBCT and this new method of assessing treatment outcomes have the potential to settle many controversies in orthodontics, such as the mechanism of functional appliances, nonextraction philosophies, molar distalization, temporomandibular effects and others.
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