## 4 Discussion
By bonding the brackets, it makes it possible to place the distalization activating unit on the buccal side of the dental arch. It not only improves the patients' comfort and reduces chairside time, which are the benefits of buccal appliances compared to the lingual appliances [22-26], but also allows the distalization force to be applied on the buccal side of the molars, which allows both distalization and distopalatal rotation. This mode of rotation is favorable in the management of Class II molar relationships as most patients with Class II have their maxillary first molars rotated mesially around their lingual roots [16, 21, 45]. In addition, the current technique has potential benefits on the periodontal status of the patients. First of all, by limiting the molar distalization activation within the maxillary arch only, the current technique avoids the proclination of the mandibular incisors compared to other inter-arch mechanics, which may cause labial alveolar bone loss and gingival recession at the mandibular incisor region [14]. Secondly, by utilizing the NiTi or SS open coil spring to distalize the molars, our technique allows for maintaining light and constant forces, which could reduce the risk of root resorption and periodontal trauma [46]. Thirdly, as the 0.018-inch SS archive used in this system could be easily adjusted and reinserted during the distalization period, a gable bend between the second premolar and first molar can be added to the archive to correct molar root angulation when needed. This modification could help reduce the chance of root proximity in the mesial and distal of the maxillary first molars and reduce the risk of periodontal disease [47]. Nevertheless, it cannot be ignored that for all maxillary molar distalization mechanics, the maxillary second molar is moved in the maxillary tuberosity, where there is abundant attached gingiva. Although not observed in the two cases presented here, there are some reports that such distalization movement could cause a deep pseudo pocket around the maxillary second molars, particularly on the distal surface of the teeth, which need periodontal management [48, 49]. However, to the authors' best knowledge, no studies have been conducted to evaluate the periodontal effects resulting from any available molar distalizers. Thus, further research on this topic is needed. \begin{table}
\begin{tabular}{c c} \hline \hline
**Indications** & **Use with Caution** \\ \hline Bilateral or unilateral maxillary & - \\ molar distalization & - \\ \hline Patients could not afford mandibular & - \\ anterior teeth proclination & - \\ \hline Amount of distalization within 4 mm & Amount of distalization larger than 4 mm (need to consider extraction of maxillary third molars and/or support from palatal TADs) \\ \hline Child/Adolescent & Adult \\ \hline Brachyfacial or mesofacial skeletal & Dolichofacial skeletal pattern (need to incorporate molar intrusion mechanics) \\ \hline Regular or deep palatal vault & Shallow palatal vault (need support from anterior palatal TADs) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The clinical indications of the modified Nance appliance usage.