Tooth transposition is a relatively rare dental abnormality in which two adjacent teeth develop and erupt in altered positions. Transposition is classified into two categories: complete and incomplete. In complete transposition, the entire crown and root of the affected tooth are observed in an altered position. In contrast, in incomplete transposition, the crown is displaced, whereas the root apex remains in a relatively normal position [1].

Tooth transposition has a relatively low prevalence. It can occur in both genders but tends to be more common in females [2]. It most commonly occurs in the maxilla, is more often unilateral than bilateral, and affects the left side more frequently than the right [3,4]. In the maxilla, transposition of the canine and first premolar is most common, whereas transposition between the lateral incisor and canine occurs with relatively lower frequency. Cases involving the central incisor, second premolar, or first molar are typically rarely reported [1].

Although the etiology of tooth transposition remains unclear, several hypotheses have been proposed, including a change in the position of the developing tooth germ, genetic influences, dental developmental abnormalities, premature loss or prolonged retention of primary teeth, trauma to primary teeth, and the presence of lesions such as cysts [5]. The transposition is frequently observed in conjunction with other dental developmental anomalies in the same patient, among which, tooth agenesis, small or peg-shaped maxillary lateral incisors, severe rotation or malposition of adjacent teeth, retained primary teeth, dilaceration, and tooth morphological anomalies are the most frequently reported [4,6]. In this regard, a study of dental anomalies associated with transposition found that 14.3% of diagnosed patients showed a peg-shaped tooth, 33% had at least one congenitally missing tooth, and other findings included supernumerary teeth, impacted teeth, and dilacerated teeth [7].

In planning treatment, several factors must be considered, including the patient’s clinical symptoms, aesthetic and functional aspects, the potential for damage to the teeth and surrounding tissues, and the duration of treatment. Available treatment options include restoration of the transposed teeth to their original position, alignment in their transposed position, or extraction of one of the transposed teeth. In general, the optimal treatment is to reposition the transposed teeth to their original positions. However, in the case of complete transposition where both the crown and root positions have been altered, returning the transposed teeth to their normal positions requires a complex treatment process and significant tooth movement, which can lead to complications such as root resorption [1,8]. Therefore, it may be preferable to align the teeth in their transposed positions.

This report presents 3 patients referred to Chosun University Dental Hospital diagnosed with complete transposition of maxillary canines and peg-shaped lateral incisors. We report here a relatively good outcome with no major complications resulting from the decision to maintain the teeth in the transposed position.

Informed consent for the publication of this case report, along with the associated clinical photographs and radiographs, was obtained from the patients’ legal guardians.

Tooth transposition is most prevalent in the maxillary canines, with the highest frequency of transposition occurring with the first premolars and to a lesser extent with the lateral incisors [3]. The cases described in this study represent a rare clinical problem, namely transposition between the maxillary canines and lateral incisors. In all 3 cases, a complete unilateral transposition of the left canine was observed. This finding is consistent with the results reported by Peck and Peck [4], who have demonstrated that tooth transposition is more often unilateral than bilateral, with the left side being more frequently affected.

The maxillary canines develop infraorbitally and superiorly to the palatal side of the first premolars and lateral incisors. During the long eruption process, the canine is transported to the mesiolabial side and can be palpated high in the labial vestibule. When deviating from the normal eruption path, the canine can be impacted or erupt ectopically from the position of another tooth. This long eruption path is one of the main factors contributing to the greater likelihood that maxillary canines will become impacted or transposed [9]. It is firmly proposed that transposition may be caused by abnormal positioning of tooth germs during early development, or by deviation of the tooth germs from their normal eruption path [10]. Alternatively, some researchers have suggested that prolonged retention or premature loss of primary teeth is the cause. It is unclear whether prolonged retention of primary canines causes canine transposition or whether the impedance of normal root resorption by canine transposition causes prolonged retention of primary canines. However, instances of retained primary canines have been reported in cases of transposed or impacted canines, which suggests that retained primary canines may be the primary cause of deviation from the eruption path of permanent teeth [11].

There are currently differing opinions regarding the relationship between tooth transposition and other dental anomalies. Although cases of dental anomalies such as microdontia, congenital missing, and impacted teeth accompanying tooth transposition have been reported, it has been argued that tooth transposition occurs independently and is unrelated to other dental anomalies. A meta-analysis evaluating dental anomalies associated with tooth transposition reported that congenital tooth agenesis was related in 20 ‒ 40% of cases, while peg-shaped teeth were associated in 10 ‒ 25% of cases. The study concluded that, while tooth transposition is frequently observed in conjunction with various dental anomalies, such as congenital tooth agenesis and peg-shaped teeth, a definitive causal relationship between these conditions has not been established [12]. In contrast, Shapira et al. [6] have suggested that transposition is primarily associated with other dental developmental disorders. Furthermore, Peck and Peck [4] have proposed that the transposition of the maxillary canines and first premolars is most probably determined by genetic influences, whereas the transposition of the maxillary canines and lateral incisors is mainly caused by displacement of the permanent tooth germs due to trauma in the primary dentition. Nevertheless, it has been suggested that genetic factors may not be entirely excluded in cases of maxillary canine-lateral incisor transposition, particularly in cases accompanied by dental anomalies such as congenitally missing or peg-shaped lateral incisors. In all our cases, there was no specific history of trauma to the primary dentition. In cases 1 and 3, the lateral incisors transposed with the left canines were observed to have a peg-shaped morphology, while the right canines exhibited malpositioning in their direction of eruption. In case 2, the patient presented with multiple congenitally missing teeth and bilateral peg-shaped lateral incisors. These findings accordingly highlight the importance of periodic radiographic assessments and a comprehensive oral examination during the late mixed dentition phase, when the maxillary canines are erupting.

In the initial decision to treat transposed teeth orthodontically without extraction, it is essential to determine whether to correct the transposed position or to align the teeth in their transposed position. From an aesthetic and functional perspective, it is generally considered ideal to align the teeth in the correct position within the dental arch. Given the early detection of tooth transposition, it may be possible to perform an interceptive treatment with minimal tissue damage. However, if the eruption of the transposed canine is significantly advanced, or in cases of complete transposition, treatment to correct the tooth to its normal position is complex and requires considerable care and time to minimize damage to the tooth and surrounding tissues. In these cases, it may be clinically advantageous to retain the tooth in the transposed position for alignment. In this case report, all patients exhibited transposed lateral incisors with peg-shaped morphology and short roots, and the affected canines had erupted significantly in a fully transposed position with the lateral incisors. It was anticipated that a significant amount of tooth movement would be required to reposition the displaced canine and lateral incisor into their original positions. However, potential complications, such as root resorption of the lateral incisors, were a cause for concern. Accordingly, maintaining the transposed position was prioritized over restoring the original position, and all cases resulted in optimal alignment without evidence of root resorption. When designing a treatment plan for orthodontic treatment of transposition, it is essential to consider multiple factors, including the patient’s occlusion, position of the root apex, esthetics, patient cooperation, stability and duration of treatment, and functional aspects.

Correcting transposition and repositioning teeth to their original positions generally requires a longer treatment duration and higher levels of patient cooperation. In contrast, maintaining the transposed position of teeth tends to involve a relatively shorter treatment period [1,8,13,14]. A review of the literature revealed that treatment durations ranged from 16 to 33 months when the teeth were maintained in their transposed positions, compared to 26 to 45 months when they were repositioned to their correct positions [8]. Kim et al. [15] compared a case in which the transposition of maxillary canines was corrected versus a case in which the transposed position was maintained, reporting average treatment durations of 24 months and 19 months, respectively. In Cases 1 and 3 of this study, the left transposed canine had significantly erupted into the oral cavity, and it was determined that repositioning it to its original location would increase the complexity of the treatment. Considering the patient’s level of cooperation and the desire for a shorter treatment period, it was decided to align the teeth while maintaining their transposed position. However, the final treatment durations for Cases 1 and 3 were relatively long, at 32 months and 26 months, respectively. Although the initial expectation was for a shorter treatment duration, the treatment period was extended due to the prioritization of careful and controlled tooth movement, which was necessary to ensure stable results. Moreover, the treatment duration was likely extended due to the concurrent orthodontic traction of the impacted right canine. Thus, planning treatment based solely on the advantage of a shorter duration when maintaining the transposed position may have limitations.

Functional and occlusal aspects of must be considered when attempting to maintain the positions of transposed canines and lateral incisors. Given that the roots of lateral incisors are thinner and shorter than those of the canines, they may be inadequate to support the occlusal function of the canines. This can lead to risks such as root resorption or compromised periodontal health if not carefully monitored. Therefore, care should be taken during or after orthodontic treatment to prevent excessive lateral forces and occlusal interferences. If the maxillary canines and lateral incisors are transposed, it is difficult to obtain an ideal canine guidance occlusion, which can affect occlusal stability. Canines play an important role in the distribution of excessive forces by inducing lateral movement; however, this function is difficult to perform in a transposed position. Consequently, in the case of transposed tooth alignment, alternative occlusal forms, such as a group function occlusion, may be considered, which requires careful occlusal adjustment to avoid occlusal disorder [5,16]. These strategies aim to reduce the potential for long-term complications, such as occlusal interference and instability.

Owing to individual differences in the shape and shade of teeth, the alignment of teeth in a transposed position can be esthetically more disadvantageous than alignment by correcting the transposition. In comparison to the adjacent lateral incisors, the canines have a high gingival line and high chroma. Having retained the canines and lateral incisors in their transposed positions, the cusps of the canines can be removed to give an appearance similar to that of incisors. Alternatively, full coverage restorations or composite resin restorations can be used for enhanced esthetics [8,17]. In particular, in these 3 cases, the affected lateral incisors exhibited a peg-shaped form, making prosthetic restoration of the lateral incisors an important consideration in the final stage of treatment. However, prosthetic restorations may not be effective in patients who have yet reached complete growth. Moreover, in cases of composite resin restorations, the shade and size of the canines differ from those of the incisors, which limits the extent to which a comprehensive incisal shape can be attained. The orthodontic treatment for 3 pediatric cases in this report was completed with the transposed canines maintained in the position of the lateral incisors. Given that the patients were in a growth phase, active interventions such as prosthetic restoration were challenging. Although there were certain differences in the size and color of the transposed left canines in cases 1 and 3, these were not severe, and from an aesthetic perspective, both the patients and their parents were satisfied with the outcomes. Therefore, treatment was concluded without any particular alteration to the tooth morphology. In Case 2, there were additional limitations during treatment due to multiple congenital missings and the necessity for a comprehensive prosthetic restoration plan for the missing teeth and microdontia after the completion of growth. Consequently, it was decided to maintain the current status until the patient had completed growth rather than actively intervene with a view toward esthetic improvement. In adolescent patients with tooth transposition, immediate intervention to improve esthetics may not be possible, and in such cases, periodic observations are necessary to maintain the current condition until the completion of growth.

One of the most prevalent complications associated with orthodontic treatment is root resorption. It is an irreversible process with a high degree of unpredictability. A number of factors have been identified as potential contributors to root resorption, including those associated with orthodontic treatment. These include the type of appliance used, the nature of tooth movement, the characteristics and magnitude of the orthodontic force, and the duration of treatment. A previous study reported that patients treated with removable appliances exhibited significantly less root resorption compared to those treated exclusively with fixed appliances, suggesting that fixed appliances have a more detrimental impact on the roots [18]. This may be attributed to the intermittent and relatively lighter forces applied by removable appliances in comparison to fixed appliances [19]. In all cases in this report, removable appliances were used during the initial stages of treatment. In particular, for Case 2, where multiple congenital tooth agenesis and short roots of peg-shaped lateral incisors were present, removable appliances were employed as much as possible, rather than fixed appliances.

Maintaining lateral incisors and canines in transposed positions during fixed orthodontic treatment presents several challenges that require careful consideration to minimize complications such as root resorption. One of the primary challenges is controlling the angulation and torque of the transposed teeth, as their altered anatomical positions often make it difficult to achieve the desired movements with standard bracket placement alone. The selection of arch wire is also a critical factor in managing transposed teeth. Initially, flexible and light arch wires are used to gently align the teeth, minimizing unnecessary stress on the roots and surrounding tissues. As treatment progresses, stiffer wires may be introduced, but the use of rectangular stainless steel wires, which exert strong forces, should be minimized as possible [20]. In these cases, the final alignment of the teeth was completed with fixed orthodontic appliances. The teeth were aligned by sequential engagement of flexible nickel-titanium wires, starting with thinner wires and progressing to thicker wires. Especially during the alignment of the erupted canines, the adjacent lateral incisors, which had short roots, were excluded from the archwire to prevent them from being subjected to excessive forces. In cases 1 and 3, torque was applied to the rectangular stainless-steel wires to adjust the inclination of the transposed lateral incisors and canines. Precise adjustments were made during this process to ensure that excessive force was not applied to the teeth.

In all three cases, the progress of treatment and the condition of the roots were evaluated through periodic radiographic examinations conducted at 3- to 6-month intervals during orthodontic treatment. In particular, for Case 1, mild root resorption of the left lateral incisor was observed in the initial radiographic examination, prompting close monitoring for any progression of root resorption throughout the treatment. Regular radiographic evaluations are essential during the treatment process to assess the progress of tooth movement and detect early signs of complications, such as root resorption.

Tooth transposition is a relatively rare developmental disorder in which the position of two adjacent teeth is altered and is frequently associated with other dental abnormalities such as congenital missing and microdontia. When planning treatment for transposition, considerations such as esthetics, function, and the potential for damage to adjacent teeth and surrounding tissues should be considered. Notably, orthodontic treatment for complete transposition can be accomplished with satisfactory results by maintaining the transposed position of the teeth. In the cases reported in this study, orthodontic treatment was performed while maintaining the completely transposed maxillary canine and peg-shaped lateral incisor in their transposed positions, resulting in satisfactory tooth alignment.