# Quantitative analysis of deviation with superimposed dental arches

**URL:** <https://discourse.slicer.org/t/quantitative-analysis-of-deviation-with-superimposed-dental-arches/27377>\
**Category:** Support\
**Tags:** registration, segmentation\
**Created:** [January 20, 2023, 1:12pm UTC](https://discourse.slicer.org/t/quantitative-analysis-of-deviation-with-superimposed-dental-arches/27377 "2023-01-20T13:12:35Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![PaVo](https://avatars.discourse-cdn.com/v4/letter/p/d78d45/32.png) [@PaVo](https://discourse.slicer.org/u/PaVo)\
**Post date:** [January 20, 2023, 1:12pm UTC](https://discourse.slicer.org/t/quantitative-analysis-of-deviation-with-superimposed-dental-arches/27377/1 "2023-01-20T13:12:35Z")

</div>

Hello everyone  
I’m quite new to the slicer software, so please be kind to the rookie 😃  
I’m doing my master thesis in the field of orthodontic tooth movement. One of my tasks is to quantitatively analyze dental arches. This means I have for example an intraoral scan (STL file) of the patients teeth (one for upper and one for lower arch) before and treatment happened, and a scan after the treatment. What I want to know is how much did every single tooth move. For this, I need to set a global coordinate system which should be the same for the compared (before and after treatment) arches. Looking at literature, there are various ways to do this. I was able to superimpose two STL models with some manually set reference points. This works quite well. I was also able to generate a deviation map. But this only indicates a more qualitative analysis. Is there a package/method where I can do the segmentation for teeth/gingiva where I get local coordinte systems for each tooth, and then calculate the translational matrix for each tooth between initial and post-treatment state? Let’s say by doing a least square fit for the corresponding teeth.

---

<div class="post-metadata">

**Author:** ![Husam\_Soboh](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/husam_soboh/32/68282_2.png) [@Husam\_Soboh](https://discourse.slicer.org/u/Husam_Soboh)\
**Post date:** [November 12, 2023, 11:47pm UTC](https://discourse.slicer.org/t/quantitative-analysis-of-deviation-with-superimposed-dental-arches/27377/2 "2023-11-12T23:47:52Z")

</div>

Hey, did you manage to find a proper way to do it? I need to do something similar and im encountering issues, the learning curve is huge.