Tooth transposition is an uncommon disorder related to ectopic eruption; it can be classified as complete or incomplete on the basis of the position of the crowns and roots of transposed teeth. Aligning the transposed teeth to a normal sequence is always complex and challenging, especially in patients with complete transposition. The segmented archwire technique with cantilever or loops has been used in many transposition patients; however, it requires considerable laboratory work and is sometimes uncomfortable for the patient. In this case report, we present a novel orthodontic treatment for an 8-year-old boy with unilateral complete transposition of the maxillary central incisor and lateral incisor (Mx.I2.I1). During the alignment stage, the lateral incisor was moved palatally to bypass the central incisor, using a 0.012-in nickel-titanium wire continuously. Active orthodontic treatment was conducted for 44 months, and the final outcome was esthetically and functionally effective. Stable and satisfactory results were achieved within 4 years of follow-up.
Highlights
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The novel treatment for transposed maxillary central and lateral incisors is reported.
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Transposed teeth were fully erupted, and the anterior alveolar bone was collapsed.
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Continuous archwire technique was used to bypass the transposed teeth.
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No fabricated loops or absolute anchorage as miniscrews were used.
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Treatment results were satisfactory and stable at the 4-year follow-up.
Tooth transposition is the positional interchange of 2 adjacent permanent teeth or the development or eruption of one tooth into a position occupied by a nonadjacent tooth. , It is a rare condition occurring in approximately 0.3%-0.4% of the general population and is more frequently seen unilaterally in the maxilla. , According to Peck, the distribution of lateral incisor-central incisor (Mx.I2.I1) transposition is 3% of the maxillary transpositions. Despite its low prevalence, treating this condition presents a major challenge to orthodontists.
To obtain the best esthetic and optimal function, teeth should be orthodontically aligned back into their normal sequence. Segmented archwire technique with cantilever or loops in rectangular wires is commonly used to achieve these results. , Using this technique, the moving and anchor parts are clearly divided, and the force system is well controlled. However, this approach requires precise laboratory work and sometimes creates discomfort for the patient. Herein, we introduce a novel method that demonstrated the successful correction of a complete maxillary central incisor-lateral incisor transposition using continuous archwire orthodontic treatment to bypass the transposed teeth. At the end of the treatment, the patient’s dental esthetic and function were successfully restored. This technique is significantly easier and faster. Its biomechanics and detailed orthodontic procedures, and 4-year follow-up records are demonstrated and discussed in this case report.
Diagnosis and etiology
An 8-year-old boy (8 years and 10 months) presented at our orthodontic clinic, mainly complaining of “space and tipping front teeth.” He was in good general health, and his medical and dental histories indicated no contraindications to dental treatment. According to his parents, he had no childhood trauma or other reasons for the delayed eruption.
The patient had a well-balanced face with good facial symmetry and a straight facial profile ( Fig 1 ). A mixed dentition with bilateral Class I molar relationship was also observed. His maxillary left central incisor was transposed with the maxillary lateral incisor, and both of their crowns were mesially tipped. The maxillary right primary molars had dental caries. Both maxillary and mandibular dental arches had ovoid shapes with normal overbite and overjet. His maxillary dental midline deviated 2.0 mm to the left. The mandibular dental midline was centered with the facial midline. His oral hygiene was fair, but the maxillary alveolar bone in the anterior segment collapsed ( Figs 1 and 2 ).
The panoramic radiograph revealed that the maxillary left central and maxillary lateral incisors were completely transposed. All permanent teeth germs (except the third molars) were present in all 4 quadrants ( Fig 3 ). The cephalometric analysis was consistent, with a Class I skeletal relationship and a good vertical growth pattern. The maxillary and mandibular incisors were normally inclined. According to the cephalometric measurements, the skeletal and dental patterns were not notably deviated ( Fig 3 ; Table ). Overall, the boy was diagnosed with Angle Class I malocclusion with complete transposition of the maxillary left central incisor and lateral incisor.
| Measurement | Chinese norm | Pretreatment | Posttreatment | 4 years posttreatment |
|---|---|---|---|---|
| SNA (°) | 82.3 ± 3.5 | 80.0 | 80.7 | 81.6 |
| SNB (°) | 78.9 ± 3.5 | 76.9 | 78.3 | 79.0 |
| ANB (°) | 3.4 ± 1.8 | 3.1 | 2.4 | 2.6 |
| Wits (mm) | −1.0 ± 1.0 | −1.7 | −2.2 | 0.6 |
| SN-MP (°) | 32.8 ± 4.2 | 37.4 | 37.9 | 37.1 |
| FH-MP (°) | 31.3 ± 5.0 | 29.0 | 28.9 | 29.0 |
| LFH (ANS-Me/N-Me) (%) | 56.8 ± 3.4 | 56.7 | 55.0 | 56.0 |
| SN-U1 (°) | 104.6 ± 6.0 | 106.5 | 109.2 | 113.6 |
| U1-NA (°) | 24.7 ± 5.2 | 26.6 | 28.5 | 32.0 |
| IMPA (°) | 89.5 ± 4.4 | 88.7 | 85.8 | 85.8 |
| L1-NB (°) | 31.0 ± 6.6 | 23.0 | 21.9 | 21.9 |
| U1/L1 (°) | 120.3 ± 10.1 | 127.4 | 127.1 | 123.4 |
| Upper lip (mm) | −2.5 ± 1.5 | 0.8 | −1.0 | −2.4 |
| Lower lip (mm) | 2.6 ± 1.5 | 2.0 | 1.3 | −0.1 |
Treatment objectives
Considering the esthetic and functional issues, the treatment objectives for this case were as follows: (1) correct the transposed maxillary incisors, (2) close the space in the maxillary anterior segment, (3) correct the angulation of the maxillary incisors, (4) correct the dental midline, (5) maintain dental and skeletal Class I relationships and achieve normal overbite and overjet, and (6) maintain facial balance.
Treatment alternatives
The following treatment alternatives were considered for the transposed teeth: (1) nonextraction treatment and alignment of the teeth in the transposed order, (2) orthodontic treatment with autotransplantation of the maxillary central incisor, and (3) nonextraction treatment and correction of the transposition to a normal tooth sequence.
Considering these treatment alternatives, the following factors were taken into account. Given that both the crown and the root were transposed in the maxillary left central incisor and lateral incisor, aligning the teeth in the transposed order would probably require a shorter treatment time than correcting the transposition. However, future prosthetic restorations are necessary for better esthetic, arch form, mastication, and speech. Considering that the patient had not yet experienced a puberty growth spurt, this approach might also impair the patient’s anterior alveolar bone growth and facial profile in the future.
Autotransplantation combined with orthodontic treatment of the maxillary central incisor is relatively easy for orthodontists but risky for oral surgeons. The recipient site for the maxillary central incisor is prepared by distally moving the lateral incisor to regain the space and the necessary bone graft for adequate alveolar bone support. The autotransplantation prognosis and further complications cannot be neglected. Meanwhile, the patient’s family was burdened with extra costs for operation procedure and endodontic treatment.
Thus, correcting the transposition to a normal tooth sequence seemed to be the best alternative, and the patient strongly desired to have his teeth aligned in their correct positions. This plan might provide the maximum esthetic with functional occlusion while maintaining the patient’s facial profile. However, it poses a high risk, and bone grafting is highly suggested to restore the anterior alveolar bone volume. Moreover, accurate tooth movement and anchorage selection were carefully considered. This plan requires a longer treatment time and effort from both the patient and the clinician.
The boy and his parents were well informed about the advantages and disadvantages of all 3 treatment plans. They rejected any surgical treatment, including bone grafting. Meanwhile, they were informed that root resorption and gingival recession were inevitable regardless of which plan they chose. After a detailed discussion, we decided to attempt the treatment that corrects the transposition to achieve a functional Class I canine and molar relationship.
Treatment progress
We started the treatment by bonding the maxillary incisors using 0.022 × 0.028-in slot straight-wire appliances (Smartclip, 3M Unitek, Monrovia, Calif). For a maximum anchorage, we used the transpalatal arch (TPA) with molar bands. A 0.019 × 0.025-in stainless steel (SS) archwire with omega stop loop was applied to preserve the maxillary arch form, whereas a 0.012-in nickel-titanium (NiTi) archwire was placed through the brackets of transposed teeth in a continuous form to palatally bypass the lateral incisor. The central incisor was mesially pulled by the power chain and labially restricted by the SS archwire. The power chain was applied for approximately 50 g of pulling force and was replaced every month ( Figs 4 and 5 , B ). We noticed a slightly gingival submersion of the NiTi wire while distally moving the lateral incisor ( Fig 5 , C ). After 3 months, when the lateral incisor palatally moved, the SS archwire and TPA were removed. To initially level the maxillary teeth, we used another 0.012-in NiTi archwire ( Fig 5 , D ).
