## 4 Discussion  
Here we showed two cases that had achieved sufficient maxillary molar distalization by utilizing the modified Nance appliance as anchorage. It is worth noting that both cases had maxillary second molars erupted into the arch before starting the distalization. Based on the clinical observation of the authors, the eruption stages of the maxillary second molars do not significantly affect the treatment efficiency of the modified Nance appliance technique. This observation is similar to the clinical results of other intra-arch maxillary molar distalizers [16; 32; 33]. There is even less distal tipping of the first molars after molar distalization when the second molars are already fully erupted [34]. In the scenario that maxillary second molars have erupted, it is unnecessary to distalize the second molars first, then to distalize the first molar. In other words, the maxillary molars can be distalized at the same time by the modified Nance appliance technique. However, a larger force should be applied when the second molars are erupted than when the second molars are not erupted [35]. On the other hand, whether the presence of a third molar follicle had a significant effect on molar distalization is controversial [32; 36; 37]. Furthermore, whether the total maxillary arch distalization affected the eruption of the third molars is also not conclusive [38; 39]. We suggest that if the position of the third molars is acceptably evaluated by the oral surgeons, germectomy or extraction of maxillary third molars right before molar distalization should be considered to utilize the effects from regional accelerator phenomenon [40]. The key factor of the modified Nance appliance is the big acrylic button, as a bigger contacting area of the palate could withstand more force under the same pressure (Force = Pressure \(\times\) Square), which means more anchorage support from the anterior palate. Since the force and counterforce are in the anterior-posterior direction during molar distalization, the depth of the palatal vault needs to be evaluated while designing the modified Nance appliance. If the patient has a shallow palate, the rugae area would be too flat to withstand the sagittal force exerted from the open coil between the second premolar and molar (Table 1). In that case, an anterior palatal TAD is suggested to be cemented with the modified Nance appliance as additional anchorage support. However, the TAD position should be planned carefully to avoid incisive canal and anterior tooth root perforation [41]. In addition, the modified Nance appliance is bonded to the premolars, which is separate from the molars. A previous study found that when distalizing the molars with the distal jet appliance, its forces tended to cause some inferior rotation of the Nance palatal button [19], thereby not only causing premolar tipping, but also increasing the risk of anchorage loss as the tight contact between the acrylic button and the palatal tissue has been lost. Thus, by separating the Nance acrylic button with maxillary molars during molar  
Figure 8: The final intraoral photos of case 2.  
distalization, the modified Nance appliance has a higher potential to hold the anchorage unit in place compared to other one-piece molar distalizers. Another unique factor that needs to be mentioned is the initial premolar brackets position that allows the insertion of the 0.018-inch SS archive right away without the need for the leveling and aligning stage. Previous studies suggested that molar distalization should be accomplished before bonding the maxillary brackets [19, 42, 43], as \"there is little anchorage value to mobilized teeth\" [44]. However, it is worth noting that the key is if there is active periodontal remodeling around the anchorage teeth, not if there are any brackets on these teeth. Thus, the premolar brackets should be bonded based on the passive draw line of the archive in relation to the first molar bands instead of the ideal bracket's position.