This case report describes the successful orthodontic treatment for a healthy woman with maxillary canine-premolar transposition associated with rare hypodontia of the contralateral canine. The treatment included extraction of the transposed maxillary right and deciduous maxillary left canines and 2 mandibular second premolars. The objectives of the treatment were to (1) correct the upper midline deviation and the occlusal plane cant, (2) move the maxillary first premolars into the canine position, (3) retract the mandibular incisors to improve the facial profile, and (4) reduce the labial protrusion. Orthodontic treatment was carried out with the lingual technique in the maxillary arch and esthetic ceramic brackets in the mandibular arch. The segmented mechanics were effective, fast, and consistently promoted the necessary movement without side effects. The smile line was improved, resulting in an ideal and esthetic gingival exposition, with the borders of the maxillary teeth following the lower lip smile curvature. The patient achieved ideal dentofacial esthetics, achieved better dental and functional occlusion, was pleased with her improved facial contour, and as a result, showed an improved self-image.
Highlights
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Maxillary canine-premolar transposition and canine hypodontia represent a significant clinical challenge.
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The article discusses aspects of these conditions, including treatment planning and biomechanics, both involving a multidisciplinary approach.
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This clinical case of transposition was successfully treated.
Dental transposition is a rare condition that involves positional interchange of 2 teeth. Maxillary canine–first premolar transposition affects approximately 0.3% of the population , , and constitutes the most common dental transposition, with an incidence of about 58%-70%. , , Genetic and multifactorial factors have an important etiologic role in this type of transposition. Environmental factors such as space discrepancy, deciduous alterations (cavities, periodontal problems, or abnormal root resorption), and dental trauma can also contribute to the ectopic eruptions of the canines. Females show a greater prevalence of transposition, and this condition can be associated with other dental alterations such as agenesis or alterations in the shape of the lateral incisors. , , The left side seems to be the more frequent location of unilateral transpositions, although the bilateral occurrence is most prevalent (11%-27% of dental anomalies). , , Another rare condition is the congenital absence of canines. The teeth that most commonly exhibit hypodontia are the most distal teeth of each dental morphologic class, namely the third molars, the lateral incisors, and the second premolars. Previous studies have shown that the prevalence of permanent maxillary canine agenesis varies between 0.07% and 0.13%. This condition has negative functional and esthetic repercussions. , From a functional point of view, the lack of a canine guide can interfere with obtaining a mutually protected occlusion in the masticatory movements and with a proper function of the temporomandibular joint. In addition, dentofacial esthetics are impaired by the lack of one of the most important components in the upper anterior region for the definition of the harmony and beauty of the smile.
Treatment alternatives for maxillary canine–first premolar transposition are dependent on the dental arch space condition, the stage of dental development, the root position of the involved teeth, periodontal conditions, and the type of malocclusion. The objective of this case report is to describe the successful treatment for a patient with maxillary canine-premolar transposition associated with rare hypodontia of the contralateral canine.
Diagnosis and etiology
A 16-year-old female sought orthodontic treatment in order to correct her anesthetic canine position and mandibular dental crowding. The patient exhibited a Class I malocclusion, with the maxillary right canine transposed in the labial position and located the distal position of the second premolar. In addition, the maxillary first premolar was mesially located in a distal position to the right lateral incisor. Absence of the permanent maxillary left canine with prolonged presence of the corresponding deciduous canine was also noticeable ( Figs 1 and 2 ). The permanent right canine showed a gingival recession and a thin osseous alveolar covering. The deciduous maxillary left canine was well positioned but had a high degree of tooth wear. The maxillary midline deviated to the right. The etiology of this transposition has a significant genetic influence because it is associated with a rare absence of contralateral left canine. , ,
Complementary observation showed that the mandibular second premolars were in a lingual position with other minor tooth irregularities resulting in a negative lower arch discrepancy.
The panoramic radiograph showed a rare absence of the maxillary left canine and an unusual position of the right canine with an extremely distal root position ( Fig 3 ). The root of the deciduous left canine was short because of physiological resorption. All third molars were present with compatible age development. Cephalometric and facial analyses indicated that the patient had a hyperdivergent growth pattern associated with a convex profile and a shallow mentolabial fold, small labial protrusion, normal nasolabial angle, and a favorable sagittal maxillomandibular relationship ( Table ).
| Variable | Pretreatment | Posttreatment | Average |
|---|---|---|---|
| SNA | 81.7 | 81.7 | 82 |
| SNB | 76.4 | 77.5 | 80 |
| ANB | 5.3 | 4.1 | 2 |
| IMPA | 100.5 | 99.9 | 87 |
| FMA | 24.4 | 23.4 | 25 |
| S-N.Gn | 71.5 | 70.9 | 76 |
| S-N.Ocl | 15.4 | 17 | 14 |
| (S-N).(Go-Me) | 36.4 | 34.8 | 32 |
| (Go-Me).Ocl | 19 | 15.1 | 18 |
| 1/.1/ | 120 | 127 | 131 |
| 1/.NS° | 103.5 | 98.3 | 103 |
| 1/.NA° | 21.8 | 18 | 22 |
| 1/-NA mm | 4.5 | 3.3 | 4 |
| 1/.NB° | 33.3 | 32 | 25 |
| 1/-NB mm | 7.4 | 6 | 4 |
Treatment objectives
Treatment options included the extraction of the transposed maxillary right canine, deciduous maxillary left canine, and 2 mandibular second premolars. The objectives of the treatment were to (1) correct the upper midline deviation and occlusal plane caused by the canine transposition, (2) place the maxillary first premolars in the canine position, (3) retract the mandibular incisors to improve the facial profile (specifically the mentolabial angle), and (4) reduce the labial protrusion. Mandibular second premolars were indicated for extractions to facilitate the alignment of the mandibular teeth and a slight retraction of the incisors to reduce the lower labial protrusion, and to improve the facial contour.
Because of esthetic concerns and wishes of the patient, we proposed an orthodontic treatment with the lingual technique in the upper arch and the use of esthetic ceramic brackets in the lower arch.
Treatment alternatives
Treatment alternatives for maxillary first premolar transposition are based on the dental arch space condition, stage of dental development, root position of the involved teeth, and type of malocclusion. The dental arch discrepancy is usually present, and to correct the arch space deficiency, extractions are recommended. Furthermore, the extraction of the 4 first premolars is the usual treatment choice for patients with Class I malocclusion. The extraction of the transposed teeth represents a good option in some instances, reducing the treatment time and complexity of the dental movements required. When the dental arch discrepancy is null or positive, and the roots are incomplete transposition, it is seldom preferred to leave the teeth in their original position. This solution has a minor esthetic disadvantage, but is significantly easier and faster, preventing root resorption and gingival recession, and it is associated with low risk of failure compared with correction of the order of the teeth. However, if the roots are partially transposed, the correction of the transposition will depend upon the gingival condition (ie, the presence of a sufficient amount of mucous tissue and on the osseous thickness [large dentoalveolar process] when attempting to move the teeth to their correct positions). In Class II malocclusion, extraction of the 2 maxillary first premolars is often required, a situation that is favorable toward correcting the transposition.
After discussing the treatment alternatives with the patient and explaining the benefits and expected outcomes, it was decided to follow the course of treatment involving the extraction of the transposed maxillary right canine, deciduous maxillary left canine, and 2 mandibular second premolars.
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