## 5 Treatment Results and Discussion  
[PERSON] et al. analyzed the treatment results of 35 patients who underwent maxillary anterior retraction by applying a CLR with a C-palatal plate [9]. In patients requiring bodily  
Figure 11: Schematic diagrams of the C-lingual retractor (CLR) and antero-posterior lingual retractor (APLR): (**a**) CLR group; (**b**) APLR group with parallel posterior tubes; (**c**) APLR group with distally angulated posterior tube. Figure 10: Biomechanics of the antero-posterior lingual retractor (APLR). tooth movement (SN-U1 \(<\) 105\({}^{\circ}\)), a long lever arm approximately 10 mm from the facial axis point (FA point) of the lingual side of the six anterior teeth was applied. Conversely, in patients requiring controlled tipping (SN-U1 \(>\) 105\({}^{\circ}\)), a short lever arm approximately 7 mm from the FA point on the lingual side of the six maxillary anterior teeth was used. The lever arms of all patients were located between the central and lateral incisors [9,36]. In the long lever arm group, SN-U1 decreased by 7.8\({}^{\circ}\), and in the short lever arm group, SN-U1 decreased by 12.0\({}^{\circ}\). In both groups, the maxillary incisors were intruded by 1.1 mm. The authors concluded that reasonable torque control and effective intrusion of the anterior teeth were possible using CLR with TSADs [9]. To our knowledge, no study has analyzed the treatment results for improving anterior protrusion using DJR; therefore, all case reports related to DJR have been reviewed, including three Class II cases [14,30,34]. [PERSON] et al. reported two extraction cases in skeletal Class II patients with anterior protrusion using DJR [23,31]. In the first case, a DJR designed to allow a helical torquing spring to be activated directly on the mini-implant was fabricated by placing two miniscrews on the palatal slope [31]. The maxillary incisors were retracted 5.0 mm and intruded 2.8 mm, with adequate maxillary incisor torque control (SN-U1, from 102.58\({}^{\circ}\) to 103.88\({}^{\circ}\)), thus, effectively reducing the anterior protrusion [31]. In the second case, treatment results showed 7 mm retraction and 1.5 mm intrusion of maxillary incisors. The maxillary first molars were extruded by 1 mm [23]. Incisal torque control during space closure was adequate. Moreover, the maxillary incisors showed a retroclination of 4.1\({}^{\circ}\) (SN-U1, from 100.2\({}^{\circ}\) to 96.1\({}^{\circ}\)) [23]. These suggest generating torque-controlled retraction and intrusion force by activating the helical spring during anterior retraction. Furthermore, [PERSON] et al. reported a case of skeletal Class II patients with an anterior protrusion in which the helical spring was activated using elastics [14]. Only the maxillary first premolars were extracted, and bodily translation of the anterior teeth was planned using DJR. Class II elastics were applied to the palatal side of the helical spring and mandibular first molar to control maxillary incisal torque. To minimize the extrusive force, elastics were worn only at night. The upper incisal torque was well-controlled (SN to U1, from 96.2\({}^{\circ}\) to 90.7\({}^{\circ}\)). When reviewing the above three cases using DJR with TSADs [2,14,31], the torque loss of the maxillary incisors was smaller than that in cases using CLR with a C-palatal plate [9]. However, additional studies with larger sample sizes are needed to confirm these results. Unlike CLR and DJR, APLR allows not only intrusion of the maxillary incisors but also intrusion of the maxillary molars. Therefore, APLR with TSADs is effective in hyperdivergent patients with lip protrusion, a gummy smile, or uprighted maxillary incisors [1,5,24]. In a case report by [PERSON] et al., a skeletal Class I patient with anterior protrusion was treated using APLR with TSADs. The maxillary incisors were retracted by 4.5 mm and intruded by 5 mm simultaneously without loss of anterior torque.