Dental transposition is an anomaly involving the positional interchange of two adjacent teeth. It is not a common anomaly, with a prevalence under 1%, but can represent a clinical challenge in our practice.
It commonly affects the maxillary arch, but can be observed also in the mandible.
Rarely it can be bilateral, and in such cases the transposition is symmetrical (same teeth affected in both sides).
In addition, some authors reported a higher frequency in female patients.
The etiology of this condition is multifactorial, involving both genetic and environmental factors.
Regarding maxillary canine – first premolar transposition, an important role of genetic factors has been documented.
Sheldon and Leena Peck provided an interesting classification of maxillary dental transposition, ordered by incidence:
- Canine–first premolar (Mx.C.P1);
- Canine–lateral incisor (Mx.C.I2);
- Canine to first molar site (Mx.C to M1);
- Lateral incisor–central incisor (Mx.I2.I1);
- Canine to central incisor site (Mx.C to I1).
In addition, a transposition can be complete or true, when both the crown and the root apex of the involved teeth are transposed, or incomplete, when only the crown is transposed but the root apex remains in its normal position.
The latter is usually a more favorable condition: since the root apex of the two involved teeth is in a normal position, is easy to move the transposed crowns to their right places with a fixed orthodontic appliance.
On the other hand, when the transposition is complete and we should interchange the position of the two adjacent teeth by moving them bodily, the decision to try to resolve the transposition is not always the best one.
Indeed, moving two teeth in opposite directions into the alveolar process to interchange their position is difficult, time-consuming, and carries a high risk of root resorption and periodontal recession.
The remaining two treatment options are the extraction of one of the two teeth, or the alignment of the arch keeping the transposition in place.
The latter option is, in most of the cases, the most viable one: it is conservative, predictable, and easier to manage.
However, achieving a satisfactory result from a functional and aesthetic point of view requires a lot of work during the finishing and refinement phase of our orthodontic treatment.
A canine and a first premolar usually show noticeable difference in color, and this should be a key-point in our treatment planning.
Furthermore, a proper torque control is needed: giving negative torque to the first premolar will remove occlusal interferences from the palatal cusp and give more buccal prominence to the root, simulating the canine bulge, while making the canine’s torque more positive will “hide” the root and provide a better gingival contour. Crown restorations and gingival recontouring can further improve the aesthetic result.
To have some treatment examples, you can read these two articles from my colleagues and me:
- Peck L, Peck S, Attia Y. Maxillary canine-first premolartransposition, associated dental anomalies and geneticbasis. Angle Orthod. 1993;63:99–109.
- Peck S, Peck L. Classification of maxillary tooth transpositions.Am J OrthodDentofacialOrthop. 1995;107:505–517.
- Ciarlantini R, Melsen B. Maxillary tooth transposition: correct oraccept? Am J OrthodDentofacialOrthop. 2007;132:385–394.