In situ rotation surgery for correction of growing, inversely impacted maxillary central incisors

Treatment of an impacted incisor with a dilacerated root is challenging for clinicians because of the position of the impacted incisor, the abnormality of the root, unfavorable prognosis, and, especially, the long treatment duration. We report on 2 young patients who had inversely impacted maxillary central incisors with developing labially dilacerated roots. Both patients were treated by a novel surgical approach, in situ rotation, by which the crowns of the inversely impacted incisors were carefully rotated to a relatively normal position, whereas the apical location remained relatively unchanged. About 2 weeks after surgery, spontaneous eruption of the treated incisors was observed. Three months later, the postoperative central incisors were further aligned into the maxillary arch with a fixed orthodontic appliance. Follow-up visits 2 or 3 years after surgery indicated that the positions of the dilacerated incisors maintained stability with good gingival esthetics, and the pulpal vitality was favorable. The roots grew further in a relatively normal direction of the incisor’s longitudinal axis, which was different from the initial curvature angle. Moreover, with the in situ rotation surgery, treatment time was greatly reduced and resulted in a favorable prognosis compared with conventional treatment.

Highlights

  • In situ rotation surgery was performed for 2 inversely impacted maxillary incisors.

  • Incisor with dilacerated root spontaneously erupted after surgery.

  • For the in situ rotation surgery, unfavorable positions were changed immediately.

  • Treatment durations were greatly shortened.

  • The developing dilacerated root grew and maintained normal pulp vitality.

The prevalence of impacted maxillary central incisors is reported to be between 0.06% and 1.4%. Although the exact causes of tooth impaction are not fully clear, studies have indicated that some systemic and/or local factors might be related to it. Systemic (general) factors refer to Cleidocranial Dysplasia, Gorlin syndrome, endocrine disorders, and so on. Local factors include supernumerary teeth, odontoma, cysts, ankylosis, and trauma to the deciduous predecessors. , The central incisor impaction not only influences the patient’s appearance, speech, and chewing function but also tends to affect the eruption and position of the adjacent teeth, , resulting in unfavorable occlusion and interproximal caries.

Interestingly, most impacted central incisors have crown or root dilacerations, and dilaceration is considered as the most common cause leading to impacted central incisors. The most common direction of a dilacerated maxillary central incisor is that the crown directs upward and labially with the root curving in a labiolingual direction. Although the cause of root dilaceration is still unclear, studies have suggested some potential causes. For example, in the development of the permanent incisor, the direction of the crown changes because of trauma to the primary predecessor. However, the Hertwig’s epithelial root sheath (HERS) of the permanent incisor remains in the original position and guides the root dentin as it would have before the trauma. As a result, further root development continues in the previous direction, which is different from the affected and shifted crown. This creates an unusual angle between the 2 parts of the tooth, preformed calcified tissue and uncalcified tissue, which results in local curvature of the longitudinal axis of the permanent incisor, leading to dilaceration. ,

Treatment of the impacted dilacerated incisors is a clinical challenge because of the impaction position, which is not easy to handle, the abnormal morphology of the root, and the long treatment duration. The conventional treatment is a 2-stage therapy. First, the crown is surgically exposed, then followed by orthodontic traction. This kind of treatment is generally successful, but it has some shortcomings. The whole treatment process is time-consuming, and the method is technically complicated. Moreover, some complications, such as ankylosis, can occur during orthodontic traction. , As a result, these kinds of impacted incisors sometimes need to be extracted or autotransplanted. Tooth extraction for young patients or adolescents always leads to local alveolar bone resorption, which may severely influence future prosthodontic rehabilitation or implantation. Autotransplantation surgery may cause deformation of the impacted incisor root, such as pulp calcification and a narrower root canal.

In this report, the authors describe a novel treatment option for the inversely impacted maxillary central incisor with dilacerated root in 2 mixed-dentition patients. After surgical exposure of the impacted central incisor crowns, the incisal edge was rotated gently and carefully to the relatively normal position, whereas the apex of the root remained almost unchanged. With this immediate reposition surgery, not only did the impacted incisor erupt spontaneously, but also the dilacerated roots continued to develop, and the growth pattern changed to a relatively normal path.

Case reports

Patient 1 was an 8-year-old girl with a complaint of an unerupted maxillary right central incisor. The intraoral examination showed that the maxillary right central incisor had not erupted ( Fig 1 , A and B ). The panoramic radiograph and spiral computed tomographic (CT) images showed that the maxillary right permanent central incisor was impacted with an incisal edge in an upward direction ( Fig 1 , D-F ). The longitudinal axis of the impacted crown was tilted labially over 90°. The root was developing toward the cervical third. An angle between the crown and root had formed, and the root dilacerated labially ( Fig 1 , F ). Based on her mother’s statement, the patient was healthy without any systemic disease. The patient was diagnosed with maxillary right permanent central incisor inverse impaction with a dilacerated developing root.

Fig 1
The intraoral and radiographic examinations for patient 1. The maxillary right central incisor was unerupted (A, B) . The condition of mandibular teeth and dentition was showed ( C ). The panoramic radiograph (D) and spiral CT images (E) showed that the maxillary right central incisor was impacted, and the crown rotated upward ( D, E ; red arrow ). The long axis of the crown was tilted labially over 90°, and the root started to dilacerate labially ( F, red arrow ).

The patient and her parents were informed of several treatment options. The first was to extract the impacted maxillary right central incisor and install an implant or fixed prosthetic when the patient was mature. The second was to extract the impacted incisor, align the maxillary dentition, and redistribute the space using fixed orthodontic appliances. Then, the maxillary right lateral incisor and canine would be managed with prosthetic restoration to replace the central incisor and lateral incisor. The third was surgical exposure and orthodontic traction, which would be time-consuming. The fourth was in situ rotation surgery followed by orthodontic alignment. The parents wished to bring out the impacted incisor and save time, so they chose the fourth treatment option.

Surgical procedure

The surgery was performed under local anesthesia. A midcrestal incision was made within the keratinized gingiva at the edentulous alveolar ridge corresponding to the impacted incisor. The incision was extended to the vestibular groove between the maxillary right lateral incisor and left central incisor. A full-thickness flap was then raised labially to gain access to the impacted incisor. The very thin labial cortical bone tissue was carefully removed to avoid any damage to the impacted incisor. After the palatal surface of the impacted incisor was exposed clearly ( Fig 2 , A ), the incisal edge was gently, slowly, and carefully rotated downward to the relatively normal position with an osteotome or an elevator ( Fig 2 , B ). It was critical to maintain the apical area of the root as a pivot point, as much unchanged as possible, during the entire rotation surgery. Then, the rotated incisor was in a relatively normal position ( Fig 2 , C ) with labial-palatal and mesial-distal mobility. The flap was repositioned and sutured with resorbable sutures ( Fig 2 , D and E ).

Fig 2
The procedure of the in situ rotation surgery for the impacted dilacerated incisor. The palatal side of the impacted incisor crown was totally exposed (A) . The incisal edge was gently turned downward (B) . The crown was rotated down more than 90° to the relatively normal position (C) . The flap was repositioned and sutured (D, E) .

Orthodontic treatment

After 2 weeks, the operated incisor erupted spontaneously, and the incisal edge was exposed inside the oral cavity ( Fig 3 , A ). Three months later, the rotated incisor erupted further, and there was no special mobility ( Fig 3 , B ). Then, the orthodontic treatment was accomplished with a fixed appliance ( Fig 3 , C ). The maxillary right central incisor was moved into a normal position after 4 months ( Fig 3 , D ). The total treatment time was about 7 and a half months. On the completion of treatment, the radiographic examination indicated that a continuous elongation of the dilacerated root was present, and the root was dilacerated again ( Fig 3 , F and G ). Based on the spiral CT image, it was observed that the root was growing, but not along the previous curved direction ( Fig 3 , H ). The developing root was in a relatively normal direction in accordance with the longitudinal axis of the erupted crown ( Fig 3 , H ). No alveolar bone resorption was observed around the 2 dilacerations. The presence of lamina dura surrounding the entire tooth socket of the incisor was identified on the spiral CT image. After orthodontic treatment, the patient wore a clear retainer for 1 year.

Apr 19, 2021 | Posted by in Orthodontics | Comments Off on In situ rotation surgery for correction of growing, inversely impacted maxillary central incisors
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