## 4 Results and Discussion
### Macro-Staging and Micro-Staging
#### 4.3.2 Micro-Staging
In cases where a combination of outward and inward hinge movement is required, they can be combined in two stages, as shown in Figure 9. However, as of the publication date of this article, no studies have been published comparing the effectiveness of pure rotation versus hinge rotation, relying only on the clinical experience of the authors. The creation of visible space between teeth seems to be an interesting way not only to reduce friction but also to improve plastic adaptability and decrease unwanted movements. A study by [PERSON] et al. [63] demonstrated in vitro how planning small diastemas between anterior teeth reduced the bowing effect of the aligner caused by passive extrusive forces  
Figure 9: The lower amines exhibit rotations of their distal ends towards lingual, requiring a correction of 32\({}^{\circ}\) (tooth 33) and 46.5\({}^{\circ}\) (tooth 43) (**A**). Differences between the two derotation micro-staging, pure rotation with the center of rotation in the center of the tooth, and hinge rotation with the center of rotation at the mesial or distal point of the tooth (**B**). The micro-staging was divided into two phases, prioritizing an initial mesial-out hinge rotation of both amines, locating the center of rotation on their mesial face (aligner #1 to #18). Then, since tooth 33 had already completed its derotation but was over-expanded, lingualization was performed (one-time derotation). Tooth 43, on the other hand, required a second hinge rotation (mesial-in), centering its center of rotation on its distal face (two-time derotation) (**C**). Result of the first set of aligners with the lower amines completely aligned without requiring overcorrection of the rotational movement (**D**). during anterior retraction in a case of first premolar extraction. Interdental spaces appear to be beneficial in cases of space closures as they increase the interproximal plastic surface and allow the aligner to access the mesial or distal aspects of target teeth, enhancing its pushing surface and system stiffness [56; 57]. Observe Precontacts or Overlaps during Movement  
Precontacts during movement, which at their maximum expression manifest as overlaps between teeth (the \"_phantom tooth_\" effect), can cause a problem during micro-staging. Clinically, we have observed that the amount of tooth overlap influences decision-making, with 1 to 3 mm considered an acceptable situation, as the increase in vertical dimension due to aligner thickness is usually sufficient to overcome the issue (with the patient being informed about the precontact stages to avoid strong chewing in the affected region). However, an overlap exceeding 3 mm can be uncomfortable for the patient and increases the risk of fracture or movement blockage, making alternative strategies worth considering. A valid option could be to manipulate the movement speed in different arches to prevent the upper and lower teeth collision from coinciding simultaneously in the same stage. Other options include cementing permanent occlusal bite blocks and removing them once the contact has been uncrossed or intruding one of the teeth to reduce the overlap to less than 3 mm and then restoring its vertical height, as shown in Figure 10.  
Another relevant situation associated with precontacts occurs during the alignment of the lower anterior teeth. If the speed of the lower alignment (by buccal crown tipping) exceeds a minimum overjet of 1 mm, there is a risk of anterior precontacts, loss of tracking, and the development of a posterior open bite. This risk can be magnified if palatal root torque of the upper incisors is programmed and the movement is underexpressed, providing a false sense of security to the orthodontist during virtual planning. In these cases, we  
Figure 10: Right upper first premolar in scissor bite (**A**). In the original micro-staging developed by the CAD designer, there was an overlap of the right lower first premolar with the upper premolar, causing a _“phantom tooth_”.