## 2 Case Presentation  
The present case report followed the guidelines of Preferred Reporting Items for Case reports in Endodontics 2020 (PRICE) [16]. Written informed consent was obtained from the patient's parents for reporting the case. An 11-year-old female presented to the private dental clinic with a chief complaint of an unerupted tooth. The patient had no relevant dental, medical, or family history. Orthodontic examination revealed the absence of the right mandibular second premolar and other occlusal discrepancies, mostly related to the unerupted tooth: mandibular midline shift (2 mm to the right), the cant of occlusal plane, Class I dental relationship on the left side, but Class II canine and Class III molar relationship on the right side and mild crowding of maxillary anterior teeth (Figure 1B-D). An impacted tooth #45 in a vertical position was observed on the panoramic radiograph (Figure 1A). Adjacent teeth were tilted, leaving no space for the impacted premolar to erupt. Two orthodontic treatment alternatives were suggested: (1) space opening for the impacted tooth to erupt spontaneously or surgical exposure and forced eruption; (2) the extraction of all second premolars, including the impacted one, and closing residual spaces using fixed orthodontic appliance [17]. After considering all benefits and risks, the patient's mother chose and agreed to the first treatment option. Bracket bonding was started in the mandibular dental arch, and an open coil spring was activated between teeth #46 and #44 to open the space for the impacted second premolar (Figure 2A). Subsequently, a bracket system was also bonded in the maxillary dental arch. Although sufficient space was created, the tooth did not erupt spontaneously. The unchanged position of an impacted tooth can be seen in the radiograph (Figure 2B). A decision was made to expose the tooth surgically and start a forced eruption [1]. Tooth #45 was exposed under local anesthesia using a closed surgical technique, and a button with a chain was bonded (Figure 2C). The traction was activated immediately, and during the following appointments, only mild vertical movement was observed in the panoramic radiograph (Figure 2D). The ankylosis of tooth #45 was suspected [18]. For the second time, surgical exposure and luxation were performed to facilitate eruption, as recommended in the literature [19; 20]. Immediate vertical traction was activated using the micro-implant, inserted between the roots of #14 and #15. The tooth moved up immediately and emerged through the gingiva. During the next appointment, a bracket was bonded to the impacted tooth, and continued traction using elastics (170 g) was initiated (Figure 2E). Due to the COVID-19 pandemic, online check-ups were performed every 4-6 weeks, and the patient continued the forced traction of tooth #45 towards the micro-implant. The next clinical examination (3 months later) revealed no further vertical movement. Interestingly, no physiological tooth mobility could be observed. Repeated ankylosis was suspected, therefore, the patient and her parents were asked whether they would agree to the additional luxation of the tooth. After parental consent, the luxation with fibertomy was performed, and elastic traction was continued [19; 20]. However, no vertical movement could be observed in the following appointment (Figure 2G,H). The patient was referred to the endodontist to assess the impacted tooth. The endodontic assessment revealed infraocclusion of tooth #45 and the gingival margin in a lower position than adjacent teeth. The tooth was free of caries. Compared to the other teeth, the observed tooth had neither response to the cold test (Pulp spray, Cerkamed, Stalowa Wola, Poland) nor sensitivity to the percussion or palpation. The periapical x-ray revealed intact _lamina dura_, normal periodontal ligament space, radiolucency in the cervical area and pulp space obliteration (Figure 2K). To confirm the diagnosis, CBCT was performed (Figure 3A-C).