Authors’ response

We thank Drs Balachandran, Mishra, and Kharbanda for their interest in our article, “Immediate changes in condylar position after rapid maxillary expansion.” We are pleased to answer their queries.

“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.” We agree that landmark plotting on multiplanar reconstruction slices is more accurate when a smaller slice thickness is used. The authors used a slice thickness of 0.4 mm, and all landmarks were measured on different slices. With this methodology, it is impossible to use the same slice to determine different landmarks that are in different planes.

“When a minimal slice thickness is used, the laterosuperior condyle and the center of the condyle cannot be seen on the same coronal slice. It is possible to visualize both points on 1 slice only when the slice thickness is equal to or greater than the anteroposterior slice differences of the center of the condyle and the laterosuperior condyle. If a greater slice thickness is used for landmark plotting, the error also would increase proportionately. Therefore, if the authors are showing both the laterosuperior condyle and the center of the condyle in the same slice, the accuracy of their work becomes questionable.”

When a minimal slice thickness is used, the laterosuperior condyle and the center of the condyle cannot be seen on same coronal slice. These points were determined in different slices of 0.4 mm. We did not use a greater slice thickness to perform landmark plotting. However, the Dolphin imaging software permits that after plotting the landmarks, they can be visualized on an image with a greater thickness. Using this new image, we could make the measurements without compromising the results. It is important that all landmarks were plotted in different slices of 0.4 mm thickness and not determined in a greater thickness slice.

“The authors also mentioned that ‘After landmark determinations, the original head orientation was again established, and the software symmetry caliper was used to obtain the… measurements…’ Correct orientation of 3-dimensional images is essential for the identification of anatomic landmarks. Small variations in head position do not influence the measurement accuracy in 3-dimensional cone-beam computed tomography images, and the authors could have done the measurements in standardized orientation. Establishing the original head orientation after landmark identification seems to be an unnecessary step.”

The measurements were made at different times. The Dolphin software symmetry caliper can only be oriented horizontally or vertically. Thus, the same head position should be repeated at different times to permit the same positioning of the caliper.

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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