## 2 Materials and Methods
### Measurement Procedure  
All measurements were obtained from the tooth 1.5 after the randomization procedure (Epidat 4.2, Galicia, Spain). Moreover, the STL5 digital file from the micro-CT (Skyscan 1176, Bruker-MicroCT, Kontich, Belgium) scan was positioned on tooth 1.5 to obtain a more accurate 3D image. The measurement procedure for the volume and area of cement remaining after lingual multibracket therapy debonding was performed by comparing the STL1 (Figure 5a) and STL3 (Figure 5b) digital files. A Boolean operation was used to achieve a boundary in the previously segmented STL1 (Figure 5c) and STL3 (Figure 5d). To identify the boundaries between both STL digital files, the STL3 was slightly over-contoured, the Boolean operation with the subsequent boundary was obtained, and then the STL3 was slightly under-contoured to its original size. Then, the area of cement remaining in the STL1 digital file was selected (Figure 5e), and a new polygon of the selected area was obtained (Figure 5g). Moreover, the area of cement remaining was selected in the STL3 through boundary selection (Figure 5f), and a new polygon was obtained (Figure 5h). The normals of this polygon were flipped, and a new polygon was created by merging the areas of Figure 5g,h, thereby obtaining a closed volume that corresponds to the remaining cement after fixed lingual multibracket appliance debonding (Figure 5i). Figure 4: Buccal perspective of the alignment rate of the segmented and aligned STL1 and STL2 (**a**), STL1 and STL3 (**b**), and STL1 and STL4, and (**d**) the buccal view of the segmented and re-aligned (**a**) STL1 and STL2 (**d**), STL1 and STL3 (**e**), and STL1 and STL4 (**f**). Reddish colors indicate an increase in volume, bluish colors indicate a decrease in volume, and green represents an accurate alignment (**g**). Figure 5: Palatal perspective of tooth 1.5 segmented on STL1 (**a**) and STL3. (**b**) Boundary creation on STL1 (**c**) and STL3. (**d**) Boundary selection of the cement remaining on STL1 (**e**) and STL3. (**f**) Mesh of the cement remaining on STL1 (**g**) and STL3 (**h**), and the combined meshes with the remaining cement after bracket removal from STL1 and STL3, obtaining a closed polygon (**i**). The volume of the cement remaining in the STL3 digital file (Figure 6a) and the mesh of the cement remaining in the STL4 digital file after cement removal (Figure 6b) for the previously segmented and re-aligned tooth 1.5 were selected and compared to analyze the volume and area of the excess cement that was not removed after cement clearance and left in the palatal area of the tooth, by means of an intersection Boolean operation (3D Geomagic Capture Wrap, 3D Systems(r), Rock Hill) (Figure 6c). Moreover, these measurement procedures were also used to analyze the volume and area of enamel damage after cement clearance by comparing the STL1 and STL4 digital files (Figure 7a-i). Additionally, the volume of orthodontic cement used to fix the lingual multibracket appliances was also measured by re-aligning the STL1 and STL2 of the previously segmented tooth 1.5, as well as the STL5 digital file from the micro-CT (Skyscan 1176, Bruker-MicroCT, Kontich) scan. The STL2 digital file (Figure 8a) was digitally filled to obtain a solid polygon  
Figure 6: Mesh of the remaining cement after fixed lingual multibracket appliance debonding present in STL3 (**a**), palatal perspective of STL4 (**b**), and mesh of the remaining cement after cement removal in STL4 (**c**). Figure 7: Palatal perspective of tooth 1.5 segmented on STL1 (**a**) and STL4. (**b**) Slight over-contouring of STL1 (**c**) and STL4. (**d**) Boundary of the enamel removed from STL1 (**e**) and STL4. (**f**) Mesh of the enamel removed from STL1 (**g**) and STL4 (**h**) and the combined meshes with the enamel removed after polishing STL1 and STL4, obtaining a closed polygon (**i**).