Authors’ response

We thank Drs Chang Ping and Li Hongbo for their interest in our article and their comments. As they mentioned, there are some considerations to evaluate the 3D soft-tissue changes by using a 3D laser scanner. First, it is important to locate the exact landmarks on the 3D images. Some points are sometimes difficult to detect repeatedly, such as zygomatic points and soft-tissue gonion. Therefore, to increase the reliability, these points were premarked manually by palpation of the face before scanning. Then the premarked points were represented together on the 3D images. This procedure enabled the investigator to assign these landmarks reliably during the repeated sessions. It is also helpful to enlarge and turn the image in a suitable direction to view certain points more accurately. Some training and education are required. However, after several practice runs, an investigator can assign the landmarks correctly with considerable accuracy.

Second, body posture, especially head posture, influences the soft-tissue measurements. In our study, the subjects sat with their heads in natural head position according to the method of Solow and Tallgren. The 2 spirit levels attached to a plastic headband were used to record and maintain the head posture. The superior spirit level was used for confirming the transverse tilting of the head, and the lateral one was used for confirming the sagittal tilting. The head posture was maintained during 3D laser scanning, and it was reproducible in preoperative and postoperative scanning.

Third, it is necessary to show the 3D changes in a more visualized way, as mentioned. The most suitable method can be a color-coding system. We used a color map showing different colors according to the different voluminal changes in the first part of our study. In the software we used, the distance from a point on the surface of the preoperative scan to the closest point on the postoperative scan was measured as a surgical change. The scans can also be registered by using the correspondence by sensitivity to movement(CSM) algorithm. This method gives the distance from a point on the preoperative scan to the corresponding point on the postoperative scan with the similar shape. These 2 methods can give different results according to the facial parts where there is considerable shape change, so the investigator should consider which method is applied in the software.

We agree that a standardized method should be established to process data to compare research by different authors. We hope that there will be advancement in the use and development of software that can soon be operated automatically in the modeling.

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Apr 13, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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