Postexpansion changes related to condylar position

We congratulate Melgaço et al for their pioneering work on postexpansion changes related to condylar positions by using cone-beam computed tomography technology (Melgaço CA, Neto JC, Jurach EM, Nojima Mda C, Nojima LI. Immediate changes in condylar position after rapid maxillary expansion. Am J Orthod Dentofacial Orthop 2014;145:771-9). We have definite queries related to the methodology in this article for landmark plotting and measurements.

The authors evaluated immediate changes (3 weeks after rapid maxillary expansion) in the position of the condyles in Class I malocclusion patients without posterior crossbite. After standardizing the head orientation, condylar position was measured by 7 parameters that used the external acoustic meatus landmarks (in 2 parameters), the center of the condyle landmarks (in all 7 parameters), and the laterosuperior condyle landmarks (in 2 parameters). All landmarks were marked on multiplanar reconstruction slices by using the Dolphin imaging software. However, the thickness of these multiplanar slices was not mentioned in the methodology; since the software provides user-defined slice thicknesses, it is important to consider this in terms of accuracy. The landmark plotting on the multiplanar slices is more accurate when a smaller slice thickness is used.

The authors mentioned that “using the coronal image slice showing the center of the condyles, this landmark [laterosuperior condyle] was obtained by the intersection of 2 lines positioned, respectively, tangentially to the most lateral and superior border of the condyles.” If we presume that the authors had used a minimal slice thickness (0.4 mm, equal to the voxel size), it is not possible to mark the most lateral point of the condyle in the slice that also shows the center of the condyle ( Fig ).

Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Postexpansion changes related to condylar position
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