## 4 Discussion  
The results obtained in the present study showed that the morphometric measurement protocol allowed for an accurate measurement technique to analyze the area and volume of the enamel removed after the interproximal enamel reduction procedure at the mesial and distal interproximal enamel surfaces. Profilometry, rugosimetry, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurement techniques have been used in order to assess the enamel surface roughness [17,18]. The SEM measurement technique provides two-dimensional (2D) analysis about the qualitative and morphological changes of the enamel surface [26]; however, profilometry and AFM measurement techniques report a three-dimensional (3D) analysis of the enamel surface roughness for subsequent evaluation [23]. In addition, profilometry and rugosimetry provide a micro-scale 3D image [27,28], whereas AFM provides a nanoscale 3D image with vertical and lateral resolution [29]. [PERSON] et al. analyzed the surface roughness of different interproximal enamel reduction procedures using rugosimetry and obtained a higher roughness (Ra) value using strip bur (0.54 \(\upmu\)m), as well as strip bands (0.41 \(\upmu\)m) and strip discs (0.34 \(\upmu\)m). In addition, interproximal enamel reduction performed with strip burs revealed the highest Vickers (vH) microhardness values (365 vH), followed by strip discs (327 vH) and strips bands (317 vH) [30]. [PERSON] et al. reported that the surface roughness performed with metal strip bands and the air-rotor stripping procedure showed statistically significant differences via SEM evaluation. However, 70% less surface roughness was observed in teeth submitted to air-rotor stripping and 30% in the teeth submitted to strip bands after the first month [31]. [PERSON] et al. analyzed the interproximal tooth enamel surface using SEM and reported that single-side diamond strip bands showed a mean enamel roughness of 15 \(\upmu\)m and ContactEZ diamond files, which also showed a mean enamel roughness of 10 \(\upmu\)m [4]. [PERSON] et al. analyzed the enamel nanotopography after interproximal enamel reduction using atomic force microscopy (AFM) and reported that the enamel surface becomes progressively smoother from burs to strips and discs to polishers. In addition, surface roughness was higher using a medium roughness strip bur (707 nm), and decreased using medium strip bands (501 nm), fine strip burs (407 nm), fine strip bands (318 nm), mesh strip discs (307 nm), curved strip discs (224 nm), and a Sof-Lex polishing device (37 nm) [32]. Nevertheless, the previously described measurement techniques do not have the capability to accurately measure the area and volume of the interproximal enamel reduction because these measurement techniques perform a qualitative observational analysis. The morphometric measurement technique allows for an accurate, repeatable, and reproducible analysis that looks at the amount of cement remaining after a fixed multibracket appliance removal, the amount of  
Figure 9: Box plot of the volume of the enamel removed after the interproximal enamel reduction procedure at the mesial and distal interproximal enamel surfaces of the STL digital files. “\(\star\)” represent outliers in line 8.  
orthodontic cement necessary to fix multibracket appliances, and the amount of enamel removed after fixed multibracket appliance removal, even in a clinical setting that prevents teeth extraction [33]. In accordance with this study, it is possible to accurately measure the area and volume of interproximal enamel surfaces (i.e., mesial and distal), independent of the width of each tooth, which is in contrast with previously published studies [19; 20]. However, some factors have been highlighted to affect the accuracy of the digital scanner and hence on the quality of the STL digital files increasing the inaccuracy of the alignment procedure.