## 3 Clinical Case Demonstrations  
### Bilateral Ditalization Case--Single Arch Treatment  
An adolescent patient presented with a mild Class II dental relationship and crowding on the maxillary arch. The patient had no significant past medical or past dental history. Intraoral examination showed the patient was in permanent dentition with all the second molars fully erupted (Figure 1). Anterior-posteriorly, there were bilateral end-on Class II canine and molar relationships, with the overjet within the normal limit. Both the maxillary and mandibular incisors were in their normal position. The maxillary dental midline was 1 mm to the left in relation to the facial midline, and the mandibular dental midline was coincident with the facial midline. There was no posterior crossbite, and the curve of Wilson was within the normal limit. The overbite and the curve of Spee were within the normal limit. There was a mild arch length discrepancy in the maxillary arch, while the mandibular arch was relatively well aligned. No significant Bolton discrepancy was detected. Scalloped alveolar bone morphology was noticed in the mandibular anterior region, indicating the thin alveolar bone support in the labial side of the mandibular anterior teeth.  
Due to the well-aligned mandibular arch and the prominent roots of mandibular incisors, it was decided not to use any inter-arch mechanics. So only the maxillary arch was treated. The treatment objectives were to (1) distalize the maxillary posterior quadrants to achieve canine and molar Class I relationships and to relieve crowding on both sides; (2) maintain the maxillary anterior teeth anterior-posteriorly and vertically, while correcting the maxillary dental midline; and (3) keep the mandibular arch untreated.  
Based on the treatment objectives, the treatment plan was designed as follows: (1) distalize the maxillary molar on both sides to super Class I with the modified Nance appliance technique, then distalize the maxillary premolars and canines to achieve Class I canine and molar relationships on both sides; (2) utilize the spaces created by maxillary posterior teeth distalization to correct maxillary anterior crowding and dental midline deviation; (3) no treatment on the mandibular arch. The treatment plan was well-accepted by the patient and parents.  
The modified Nance appliance with a big acrylic button as the anchorage was delivered with mesh pads cemented to four maxillary premolars (Figure 2, left). Next, maxillary premolar brackets were bonded, and the segmental 0.018 SS-inch archives with open coil springs were delivered as described above. The open coil springs were kept active until a super Class I molar relationship was achieved bilaterally (Figure 2, middle; Figure 3). Then, the appliance was removed, and a new Nance appliance with a big acrylic button  
Figure 1: The initial intraoral photos of case 1. Scalloped alveolar bone morphology was noticed in the mandibular anterior region.  
connecting to the maxillary first molar bands was fabricated and cemented (Figure 2, right). Next, the rest of the maxillary arch was bonded, and leveled and aligned starting with continuous NiTi archive and then 0.018-inch SS archive. At the same time, the maxillary left premolars and canine were distalized by power chaining canine and premolars to the first molar (Figure 2, right).  
After premolars and canines were distalized, enough spaces had been created to correct maxillary anterior crowding and maxillary dental midline deviation. The treatment of the maxillary arch was finished on a rectangular SS archive (Figure 4). At the end of the treatment, bilateral Class I canine and molar relationships were achieved, with a well-aligned maxillary arch, ideal overbite and overjet, as well as functional and esthetic occlusion (Figure 5).