## 2 Case Report  
A pediatric patient had a chief complaint of anterior crossbite. Her frontal view was almost symmetrical, and the facial profile was straight (Figure 1). She had no family history of Class III malocclusion. Her overjet was \(-\)2.0 mm, and overbite was 3.0 mm. The terminal plane was a mesial step type on both sides. Severe crowding was observed in both arches and the left mandibular anterior teeth showed abnormal morphology. She had an MNTI diagnosis at the age of 8 months in oral surgery, and surgical resection was considered and proposed. However, her parents did not approve of surgery because it was the most invasive and unimaginable option for them. Therefore, she was followed closely without aggressive treatment for a period of time. A month after the  
Figure 1: Pretreatment facial and intraoral photographs. (**A**) Lateral view; (**B**) frontal view; (**C**) right molar relationship; (**D**) centric occlusion; (**E**) left molar relationship; (**F**) overjet; (**G**) mirror view (maximally); (**H**) mirror view (mandibular). MNTI diagnosis, the reduction in the size of the tumor could be confirmed by clinical examination, computed tomography (CT) scans, and magnetic resonance imaging (MRI), though she did not receive aggressive treatment. Her MNTI indicated a similar reduction tendency every year, and still no evidence of progression has been found. Cephalometric analysis, when compared with the Japanese norm, showed a skeletal Class III jaw-base relationship (ANB, \(-2.0\lx@arcdegree\)) because of mandibular overgrowth (SNB, \(82.5\lx@arcdegree\)). Wits value was \(-7.0\) mm. The mandibular plane angle was within the normal range (Mp-SN plane, \(34.2\lx@arcdegree\)). The upper and lower incisors were limigually inclined (U1-SN, \(97.0\lx@arcdegree\) and L1-Mand. pl., \(80.6\lx@arcdegree\)), and it resulted in an increase of the interincisal angle (\(148.2\lx@arcdegree\)). A panoramic radiograph showed the lack of eruption spaces for the permanent teeth (Figure 2). Though we listed these problems as previously described, we were deeply concerned about orthodontic treatment for the patient with MNTI because of an unprecedented case. Furthermore, we had worried about the stimulation of MNTI on the mandible by changing her occlusal position with orthodontic treatment. Therefore, we sufficiently explained the risk to her and her parents that there was a possibility that her tumor progression would be induced by orthodontic treatment, and we would have to discontinue orthodontic treatment if any such symptoms appeared. However, they strongly preferred orthodontic treatment and expressed that they would be responsible for whatever occurred. Thus, we formed a treatment plan. Our proposed therapy consisted of maxillary protraction and slow maxillary expansion. The mechanical device was a facemask combined with a removable expansion plate. The maxillary protection could help to accelerate the maxillary growth. Moreover, activating cells in the maxillary sutures by the combination of maxillary expansion appliance would enhance an effect of maxillary protraction, and its device also helped to create eruption spaces for the permanent teeth. It was somewhat concerning that one of the supporting points of the facemask was her chin. Therefore, we explained sufficiently to her and her family that orthodontic treatment posed a risk of worsening MNTI once again. As it did not make them falter in their determination to the treatment, her orthodontic treatment was initiated. She was evaluated regularly for signs of advancing MNTI deterioration as before in oral surgery. At the age of 7 years and 9 months, maxillary expansion was performed by a removable expansion plate firstly. The plate included the anterior springs that tipped upper incisors buccally and the hooks that were placed in the canine region for a facemask. She was instructed to use it every night and turn the expansion screws weekly on the specified day of week (1/4 turn: 0.25 mm).