Case report
Orthodontic uprighting of severely impacted mandibular second molars

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The prevalence of impacted second molars is low, varying from 0% to 2.3%. The etiology of an impaction can involve systemic, local, and periodontal factors, as well as a developmental disruption of the tooth germ. A number of surgical and orthodontic treatment options have been suggested in the literature, including leaving the tooth in situ, removing the impacted second molar, orthodontic uprighting, and autotransplantation. Removal of third molars has been suggested as an adjunct for space creation. This article presents the treatment of a girl with bilateral severely impacted mandibular second molars as well as an ectopic maxillary left canine and severe crowding affecting both the maxillary and mandibular arches. Her treatment was successfully completed with fixed preadjusted edgewise appliances (0.022 × 0.028-in slot size) and MBT prescription (APC precoated Gemini Brackets; 3M Unitek, St. Paul, Minn), along with the removal of 4 first premolars. The maxillary left canine and the mandibular second molars were surgically exposed. The treatment mechanics show that even severely impacted second molars can be uprighted by routine straight-wire techniques, which are easy to apply. The center of rotation of the second molar lies in the bifurcation of the roots of this tooth, and this biomechanical property was used to its full advantage. The techniques applied comprised bracket repositioning, bypass of brackets, conversion of molar tubes to brackets, thermoelastic copper-nickel-titanium archwires, and a push-coil spring. Other orthodontic treatment mechanics, which require complex sectional or segmental techniques, auxiliaries, or artistic wire bending, that have been suggested in the literature were not used here. The third molars were not removed.

Section snippets

Diagnosis and etiology

A 9-year-old female patient was referred to the orthodontic department of Guy's and St Thomas' NHS Dental Hospital Trust, London, United Kingdom, because of delayed eruption of the maxillary left central incisor. She was diagnosed with a Class I incisor relationship in the early mixed dentition with crowding affecting both the maxillary and the mandibular arches. Both maxillary deciduous canines were removed to relieve the crowding in the labial segment (Fig 1). On review 6 months later, the

Treatment objectives

The objectives of the orthodontic treatment were to (1) align the impacted teeth (ectopic maxillary left canine and mandibular second molars), (2) level the arches, (3) correct the crossbite, (4) reduce the overbite while maintaining the overjet, (5) improve the maxillary incisor inclination, (6) close the residual extraction spaces, (7) correct the molar relationship, and (8) coordinate the arches.

The orthodontic treatment mechanics included exposure of the ectopic maxillary left canine and

Treatment alternatives

Treatment modalities for impacted mandibular second permanent molars include orthodontic alignment and surgical repositioning. In view of the patient's age and the early stage of third molar development, autotransplantation of the third molar after extraction of the second molar was not thought to be a good alternative. Surgical repositioning of the mesially impacted molar could be complicated by ankylosis, resorption, and loss of tooth vitality. Orthodontically assisted guided eruption would

Treatment progress

At the start of treatment, the impacted and ectopic maxillary left canine was exposed (surgically repositioned flap with gold chin attached). A fixed preadjusted edgewise appliance (MBT prescription with a 0.022 × 0.028-in slot size) was placed in the maxillary arch with convertible bands fitted on all first molars (3M Unitek). Posterior pull headgear with a force of 300 g per side was worn a minimum of 12 hours per day. The maxillary left lateral incisor was not bonded until 6 months after the

Treatment results

Overall, the orthodontic treatment achieved the planned occlusal and facial esthetic goals (Fig 6, Fig 7, Fig 8, Table). All impacted teeth, including the horizontally impacted mandibular left second molar, were brought successfully into occlusion. The alignment of the mandibular second molars did not necessitate removal of the third molars, and there was a slight overcorrection of the previously impacted mandibular left second molar. Both arches were well aligned with good incisal and buccal

Discussion

Various methods of molar uprighting have been described in the literature. When the molar is severely displaced, such as the ones described here, a continuous wire that uprights the molar is often thought to cause undesirable movement of the anchorage teeth such as tipping, rotation, intrusion, or extrusion of the adjacent teeth. Segmented mechanics have been advocated to prevent such side effects (T-loop spring10), and sectional uprighting springs have been designed for this specific purpose:

Conclusions

The management of impacted second molars is an orthodontic challenge. Although many orthodontic treatment mechanics encompassing different levels of complexity have been described in the literature, routine straight-wire mechanics as presented here are a useful alternative.

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