Orthodontic management of a borderline case with ectopic maxillary canine by unilateral premolar extractions.

Management of orthodontic cases often requires extraction of permanent teeth. The decision making regarding extractions depends upon the arch length tooth material discrepancies, the growth pattern, general profile, and arch asymmetries. Unique orthodontic problems may command special treatment lines to be taken. The present report describes a case with unilateral buccally blocked out canine and bilateral posterior crossbite, for which unilateral premolar extractions were performed achieve esthetic and functionally stable occlusion.

Introduction

Extraction is done primarily to gain space, retract, and correct sagittal interarch discrepancy. All other things are equal, it is better not to extract, but in some cases extraction provides the best treatment. The decision making regarding extraction of teeth depends upon the arch length tooth material discrepancy, facial profile, and skeletal pattern.[1] Certain patients with unique orthodontic problems such as jaw size/tooth size discrepancies, contra-lateral tooth size differences, and maxillary/mandibular tooth size disharmonies demand asymmetric extraction.[234] Ectopic canines which are buccally displaced usually result from space deficiencies; thus, the management often dictates extraction as the treatment protocol.[5]

The present article describes a case of a patient with Class II subdivision malocclusion with unilateral buccally blocked canine which was treated by unilateral first premolar extractions.

Case Report

A 15-year-old female patient had reported to the Department of Orthodontics with the chief complaint of a malpositioned upper left tooth. A clinical examination of the patient was done. It was observed that the patient had a symmetrical mesoprosopic face. The patient had a convex profile and a prominent nose. The smile arc of the patient was nonconsonant [Figure 1].

Figure 1

Pretreatment photographs

On intraoral examination, it was observed that the maxillary midline was shifted toward the left and the mandibular midline was shifted toward the right; canine relation was Class I on the right side and a buccally blocked canine was present on the left side. Anteriorly, the overbite was in an edge to edge relation. The patient had a Class I molar relation on the right side and Class II molar relation on the left side. The patient had bilateral posterior crossbite with respect to the first molars [Figure 1].

The maxillary arch was U-shaped and symmetric, and the mandibular arch was wide, symmetric, and U-shaped.

The cephalometric findings revealed a normodivergent growth pattern with a Class I skeletal base [Figure 2].

Figure 2

Pretreatment cephalogram

An orthopantomogram was also recorded which showed erupting third molars in all four quadrants [Figure 3].

Figure 3

Pretreatment orthopantomogram

Treatment plan

On considering the diagnostic criteria, a decision was made for unilateral first premolar extractions alignment of the dentition into the arches and correction of bilateral posterior crossbite.

Treatment progress

Preadjusted edgewise MBT.022 slot brackets were bonded in both arches, and initial alignment was done using 016 NiTi wire without involving the blocked out canine into the continuous wire. A NiTi expander was inserted for correction of posterior crossbite. An archwire sequence of 018 NiTi, 016 × 022 NiTi, and 017 × 025 NiTi was followed. Extraction of maxillary right first premolar was performed. An open coil spring was placed with respect to the blocked out canine for space creation and midline correction in the maxillary arch [Figure 4]. After sufficient space had been created, the left maxillary canine was bonded and aligned within the arch using active lacebacks. Mandibular right first premolar was extracted to maintain the canine relation and the overbite. Mandibular left canine was retracted into the extraction space using closed coil spring. Space created was used for midline correction and the correction of crowding of the mandibular incisors.

Figure 4

Unilateral extraction in maxillary arch and NiTi palatal expander for correction of crossbite

A 019 × 025 SS wire was placed in both arches for 6 weeks along with asymmetric elastics for achieving a canine guided occlusion [Figure 5].

Figure 5

Asymmetric elastics

Bracket repositioning was done and 014 NiTi wires were used for final finishing and detailing.

Treatment results

An ideal Class I occlusion was achieved in the patient with a positive overjet and overbite. The smile appearance improved and the esthetic profile of the patient was maintained [Figures 6 and 7 and Table 1]. Post treatment Orthopantomogram showed ideal mesiodistal angulations of the dentition [Figure 8].

Figure 6

Posttreatment photographs

Figure 7

Posttreatment cephalogram

Table 1

Cephalometric comparison

Figure 8

Posttreatment orthopantomogram

Discussion

The present case was of a nongrowing female patient with ectopic canine and bilateral posterior crossbite in the premolar-molar segment.

Malocclusions with ectopically erupted canines are often treated by all four first premolar extractions. The decision regarding extraction or nonextraction treatment plan is based on the amount of arch length tooth material discrepancy and the facial profile of the patient. According to Proffit and Fields, tooth size-arch length discrepancies below 4 mm tooth extraction is rarely required, whereas discrepancies between 5 mm and 9 mm allow treatment to be performed with or without extractions, depending on the characteristics of the patient.[6] In our patient, the tooth size-arch length discrepancy was 8 mm in the maxillary arch and 3.5 mm in the mandibular arch. Thus, it did not indicate extraction of all first premolars as is routinely followed in cases with ectopic canines. Further, the facial profile of the patient is an important factor in determining the need for extractions. According to Ramos et al., 1 mm of retraction of the upper incisors the upper lip retracts 0.75 mm.[7] Incisor retraction of 1 mm results in 0.64 mm of upper lip retraction.[8] For every 1 mm of lower incisor retraction, lower lip retracts 0.6 mm.[9] Thus, space closure performed by retracting anterior teeth tends to render the profile more concave. In our case, the patient had a pleasing profile. Thus, it did not indicate extraction of all four first premolars which would have resulted in a retrusive profile. A treatment plan was devised such that space could be created for the blocked out canine along with midline correction. Extraction of premolars was performed on the side opposite to the buccally displaced canine for space creation and maintenance of a canine guided occlusion. While correcting the position of a blocked out highly placed canine, it should not be engaged in the continuous wire so as to avoid the intrusive side effect on the adjacent dentition. Once the canine is brought close to the occlusal plane, it can be aligned into the arch using continuous mechanics.

Asymmetric elastics were required in this patient for final coordination of maxillary and mandibular midlines. Excessive midline shift can occur as a result of unilateral extractions; thus, coordination of midlines should be undertaken carefully in such cases.

Conclusion

Unilateral extractions can give excellent esthetic results with stable occlusion. Care must be taken to prevent midline shift and development of arch asymmetry during such treatment methods. An ideal Class I occlusion was achieved in the case with improved smile esthetics while maintaining the pleasing profile of the patient.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.