## 3 RE Process as \"Game Changer\": Clinical Applications
### Treatment Plan  
#### 3.2.1 Orthodontic Setup  
The orthodontic setup was part of the diagnostic process since the analogical era. The diagnostic setup was initially proposed by [PERSON] [23] and served as a practical aid in treatment planning and diagnosis, especially in complex cases or in the presence of significant dento-alveolar compensations. It is a valuable aid in testing to confirm, modify, or reject a suggested treatment plan. The diagnostic setup involves trimming (analogical) or segmenting individual teeth and moving each tooth to its desired position. The advantages of diagnostic setup are mainly: (1) determining and visualizing the resultant occlusion; (2) tooth size/arch length discrepancies can be better optimized; and (3) the individual need for interpersonal reduction or dental extractions to solve crowding or dental protrusion can be predicted [24].  
With the advent of digital systems, the orthodontic setup has become a pillar of the digital workflow for orthodontic treatment, especially with clear aligners. In this regard, RE systems allow clinicians to set up customized treatment plans. Clinicians can generate multiple digital setups using clear-aligner software when deciding between different treatment decisions. For example, in the case of mandibular anterior crowding, the clinician may ask for two different setups: one excluding IPR to evaluate the final proclination of the incisors and the overjet, and the second including IPR. Alternatively, the clinician may ask for one setup with mandibular IPR and then a second setup with the extraction of one mandibular incisor to compare the two treatment options. Figure 9 shows the example of a diagnostic setup with two different options for treating lower arch crowding in a patient with severe periodontal disease (Figure 10).  
However, the more significant innovation in the clear aligner treatment (CAT) is the possibility of establishing and visualizing outcomes before treatment and, accordingly, customizing the appropriate biomechanics. Clinicians can stage the orthodontic treatment in a specific sequence by staging the type of tooth in the software program. They can also modulate the rate of tooth movement at each step, setting specific limitations [25]. Thus, CAT requires a more \"proactive\" disciplined approach than fixed orthodontic appliances; however, the most recent literature suggests that the predictability of orthodontic movement with aligners still has limitations related to the biomechanics of the system, which can be different according to the type of movement programmed. Consequently, appropriate virtual treatment plan design, including overcorrection, usage of auxiliaries, proper selection of attachment design, and supplementary refinement stage, are warmly encouraged to increase the system's predictability [26]. To emphasize this concept, Figure 11  
Figure 10: Example of diagnostic setup with Invisalign system (Align Technology, San Jose, CA, USA) planned to decide the best treatment option. (**A**), Pre-treatment condition; (**B**), first setup with extraction of lower right first premolar; (**C**), second setup with extraction of lower right canine.  
shows the expected treatment outcomes (Treatment Plan 1) and the pre-refinement clinical outcomes, with complete correction of the class II malocclusion that was accomplished by setting the usage of inter-maximillary elastics in the system from a specific stage of the treatment. A number of 3/16 inter-maximillary elastics were worn 22 h per day with different release of forces (2.5 once on the right side and 4.5 once on the left side) since the class II occlusal relationship was more severe on the right side; however, there was an incomplete correction of the deep bite that has required additional aligners. This incomplete result could be attributed to the absence of adequate overcorrection of the vertical malocclusion into the digital setup.