INTRODUCTION

Transposition of teeth is a rare condition, with a prevalence of about 0.3–0.4% in the general population.1–4 It is an eruption anomaly characterized by a change in position of two adjacent teeth.15 Usually, transposition involves the canine and the first premolar46–8 or lateral incisor,1249–11 but transposition of the central incisors has also been reported.12–14 Five different types of transposition have been described in the upper arch45 and only two in the lower arch.15 Transposition can occur on both sides or only one,6716–18 with the left side more commonly affected in both sexes.

Transposition is considered real or complete when the teeth have totally exchanged their position in the arch and their roots are parallel to each other.239 It is called partial or incomplete when the tooth positions are not completely exchanged.239 The diagnosis of transposition should not be confused with simple ectopic eruption. All transpositions are ectopic eruptions, but only a few ectopic eruptions may be considered transpositions.1 In canine–lateral incisor transposition cases, the position of the canine root apex should be mesial to the lateral incisor, and in canine–first premolar cases, it should be distal to the first premolar.12 Other dental abnormalities, frequently associated with the transposition phenomenon, are missing or peg-shaped upper lateral incisors, retention of deciduous canines, tooth rotation, and malposition of adjacent teeth.238–10

Pathopaleontological findings have shown the presence of tooth transposition in prehistoric man in Southern Asia and North America,151920 so it cannot be considered a disharmony of modern times.

Although the causes of transposition have not yet been completely established, many theories have been suggested to explain this process. Trauma,221 retention or early loss of primary teeth,22 transposition of the anlage of the teeth during odontogenesis,223 and intraosseous migration of teeth away from their normal path of eruption2324 have all been considered to be causative factors. Peck and Peck4 reported that in canine–first premolar transposition, retention, trauma, and early loss of primary teeth were not considered relevant factors. Some authors16172325 described nearly identical bilateral transpositions in siblings and have considered genetic factors responsible for tooth transposition. Recent evidence has shown a genetic influence within a multifactorial inheritance model, and the high frequency of associated dental anomalies plus family and bilateral occurrences support the case for polygenic causes.4

The upper permanent canine develops under the orbit in a superior and palatal relation to the first premolar and lateral incisor. During its long path of eruption, the canine moves labially and mesially and can be palpated high in the labial sulcus.26 For some reason, it can turn away from its path either mesially or distally, creating the possibility for transposition.13

The most common type of tooth transposition is that of the upper canine–first premolar. Usually the canine is rotated in a mesiobuccal direction, and the first premolar is tipped distally and rotated mesiopalatally. The upper deciduous canine is often present, creating an arch length discrepancy problem.4 The canine is usually blocked out to the buccal between the first and second premolars, but in some cases it can be seen in a palatal position, especially in cases of canine and lateral incisor transposition.10

Although several reports on maxillary canine and first premolar transposition can be found in the literature, very few include treatment procedures.51011 Several authors showed orthodontically treated cases that maintained the transposed teeth in their original positions.67142728 Only one article presented a case of bilateral canine and first premolar transposition, with missing lateral incisors, that was treated by reversing the transposed teeth. This was done only on the right side, and the primary canine was maintained in the lateral incisor position.18

In this article, a case of maxillary bilateral canine–first premolar transposition with missing lateral incisors was treated orthodontically by reversing the transposed teeth on both sides of the arch and closing the lateral incisor spaces. This approach was justified by the undesirability of having the first premolar in contact with the central incisors.

Case presentation

A nine-year, five-month-old female patient presented with parents who were worried about the delayed eruption of the permanent lateral incisors. The patient was in the mixed dentition and presented a Class I molar and canine malocclusion with slight lower anterior crowding. She also presented regular oral hygiene and healthy periodontal tissues. The facial profile was convex, showing no muscle strain or pressure, and lip closure was normal with a pleasant smile (Figure 1).

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Panoramic and periapical radiographs showed the bilateral absence of the upper lateral incisors and the transposition of both upper canines with the first premolars (Figure 2). Both canines were located between the first and second premolars. The cephalometric measurements showed a vertical growth tendency (Figure 3; Tables 1 and 2). No cephalometric or dental discrepancy was present (Table 2). Facial convexity was greater than normal, which was favorable in missing lateral incisor cases when planning to close the spaces of the missing teeth.

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TABLE 1.  Initial and Final Ricketts 10 Factors Analysis Data^a

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TABLE 2.  Initial and Final Facial Descriptions (Facial Pattern—Dolicho, Meso, or Brachi), Discrepancies, and SNA and SNB angles^a,b

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The radiographic and clinical evaluation indicated a very early stage of development to start treatment. However, treatment planning for correction of the transposed teeth and closure of the missing lateral incisor spaces was possible (Figures 4–8). The upper deciduous second molars (55, 65) and deciduous lateral incisors (52, 62) were removed, allowing closure of the missing lateral incisor spaces and mesial movement of the permanent upper first molars to a Class II relationship (Figures 6b,c). The upper deciduous canines and deciduous first molars (53, 63, 54, 64) were removed three months later to correct the transposition (Figures 6d).

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A straight-wire 0.018 × 0.025–inch fixed appliance was placed when the patient was 10 years, two months old and the upper premolars were erupting (Figures 4 and 6e). The treatment plan consisted of reversing the transposed teeth, moving the upper first premolars palatally (Figure 6f) to allow the canines to move mesially through the alveolar bone, avoiding contact with the maxillary labial cortical bone. The upper canines were moved mesially as far as possible inside the alveolar bone toward the lateral incisor spaces (Figures 5 and 6g), whereas leveling and alignment were done with round 0.014 to 0.018 inch stainless steel archwires.

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Considering the limitations presented by the case, the follow-up records show a very good result because all treatment goals were fulfilled. Only a small amount of alveolar crest bone height was lost, and only a clinically insignificant amount of root resorption could be seen on the final panoramic and periapical radiographs (Figure 9). Final cephalometrics measurements (Figure 10; Tables 1 and 2) showed the same facial balance as that at the beginning of treatment, demonstrating that space closure produced no negative influence on the middle third of the face.

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The patient's records taken seven years and seven months after treatment show the excellent stability of the occlusion and facial balance. No spaces are present in the upper arch, the posterior occlusion presents an acceptable intercuspation (Figures 11 and 12), and there is correct root angulation of the teeth (Figure 13).

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Figure 5 shows the risk in reversing transposed teeth. The alveolar bone width is always too narrow to allow both teeth to move inside it. The first premolar has to be moved palatally to avoid any damage to the labial cortical bone or root interference or resorption (Figure 6f). After the canine was moved mesially, the fist premolars were brought back to the alveolar bone, and leveling and alignment were completed. During the leveling phase, Class III elastics or a face mask were used to bring the upper teeth forward to a Class II relationship (Figure 6g,h). Ideal 0.018 × 0.025–inch arches were placed with individual lingual root torque on the upper canines and with labial root torque on the first premolars (Figure 7). The fixed appliance was removed after four years and nine months of treatment (Figure 8), and the patient received an upper removable and a lower canine-to-canine fixed retainer.

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DISCUSSION

When teeth are transposed, their natural sequence in the arch is changed, leading to functional and esthetic problems, especially if the transposed teeth are grossly out of arch alignment. If transposition is associated with a malocclusion, the case becomes even more difficult to treat and the prognosis worsens.

It is surprising that publications on this matter are sporadic and limited to case reports with no treatment.13–512 The case presented here is difficult to treat because of bilateral teeth transposition and lateral incisor agenesis. The common procedure has been to maintain the teeth in their original positions, with the first premolars coming in contact with the lateral incisor.6729 In a similar case, Laptook and Silling18 reversed only the right side and kept both upper lateral incisor spaces for implants or prostheses.

During treatment planning, one has to define if it is possible to correct the tooth order in the arch and if there is an advantage in closing the congenitally missing lateral incisor space. Aspects that have to be considered include difficulty, time, risks, esthetics, function, stability, biological sacrifice or damage, mechanic device, professional preference, and experience.

I have treated many cases of transposed teeth of different types and five cases were treated orthodontically without correcting the tooth order. These showed a poor result as compared with cases treated by reversing the tooth order. Based on these experiences, my personal preference is always to reverse the tooth order when possible. The difficulties are great, but with good control of force direction, you will be successful.

Some literature refers to the reversal of tooth transposition as heroic orthodontics. Surely, it is not a treatment for a novice without good orientation. The torque control and movement of the transposed teeth while preserving the vestibular cortical bone plate and the gingival level are great orthodontic difficulties.

Obviously, this approach needs more treatment time, and treatment time is often the key in judging treatment results. However, the stability, esthetics, and function are benefited. When one has an upper canine between the upper premolars, the functional movements and stability are worse then when a canine is placed in the lateral site. Sometimes one has to make a premolar crown on the canine and give it a palatal cusp to stabilize the occlusion.

In this particular case, the treatment time was four years and nine months, but the patient missed five strategic visits and failed in elastic and facial mask use, which delayed the treatment and resulted in not totally closing all the spaces. The real treatment time took four years and four months, but the result can be considered very good, despite the risks involved and the patient cooperation problems. Negligence in oral hygiene favored decalcifications and cavities that esthetically compromised the result. This probably made the maxillary canines look “aged” and made necessary some posttreatment fillings, a root canal, and a crown on the left lower first molar (36). This outcome is not directly related to the transposition treatment, but to patient cooperation.

Maxillary canine–first premolar transposition is often associated with upper lateral agenesis. The treatment solution options for this situation are implant, prosthesis, or orthodontic space closure. The decision is based on advantages and disadvantages. In this case, the facial profile, the facial mild third convexity, the smile height, the cephalometric jaw relationship associated with the patient, and parent's opinion favored the decision to close the lateral agenesis space. The option whether to close the spaces or not in the cases of maxillary lateral agenesis is always a matter of great controversy mainly because the treatment becomes longer and more difficult, compared with an implant placement. Some authors prefer an implant or prosthetic solution because they believe some aspects of the space closure to be disadvantageous. When the option is to close the space of the upper lateral agenesis, one relies on some important variables such as the different color, shape, and size of the canine in the lateral site, the different root prominence, and the different height of the gingival scallops. Would not this be the price to pay? The root resorption level and the gingival contour are a little higher but are at acceptable levels without significant biological damage. The patient's opinion was reported as happy with her smile and appearance and happy because she is not using a prosthetic device.

Considering the patient's esthetics and age, it is difficult to understand the treatment approach that requires a 14-year-old to use a removable prosthesis until she is 18 and can receive a fixed prosthesis or implant. This is the only case report treated by reversing the bilateral transposition and orthodontically closing the upper lateral incisor spaces. This approach is a realistic treatment plan. It is easy to tell the patient that he will need to use prosthesis or implant when he is older and can pay for it. On the other hand, we have to consider that the use of a removable retainer with anterior teeth on it during adolescence is not a very easy situation for the patient. We choose this orthodontic approach because once it was decided to close the congenitally missing upper lateral incisor spaces, it was inappropriate to position the upper first premolars in contact with the central incisors.

In 20 years of treating various types of teeth transpositions in both jaws, I am convinced that orthodontically reversing transposed teeth is a viable possibility in the majority of cases. All treatment risks should be considered, and special attention should be given to esthetics, occlusion, canine apex position, root resorption, periodontal structures, and the patient's age. Although in some situations function and esthetics demand correction, the key to success is to develop well-controlled orthodontic procedures to decrease the potential risks and lessen the possibilities for unsuccessful treatment. The treatment time in this case was 57 months, but the results reinforced by the long-term records make this treatment very good despite the risks involved.

CONCLUSIONS

Many case reports of uncorrected dental transpositions have been published, but most of them report orthodontic treatment restricted to alignment and leveling of the transposed teeth in their original reversed positions. This case report is a new approach in orthodontics for the treatment of tooth transposition. We believe that it is possible to orthodontically treat this challenging anomaly in an efficient way.8101130–32 Although this treatment approach can and should be done, one must always consider the physiological limits and avoid procedures which could damage periodontal structures or cause root resorption.