Transposed Teeth

Tooth transposition is a positional interchange of two adjacent teeth.

Definition: it is defined as an interchange in the position of two permanent adjacent teeth located in the same quadrant in the dental arch.

Tooth transposition is considered a rare condition and is usually related to eruption disturbances of the teeth and to the subsequent abnormal occlusal relationships.

Also defined as the positional interchange of two neighbouring teeth and especially of their roots, or the development or eruption of a tooth in a position normally occupied by a non-neighboring tooth. It is a peculiar type of ectopic eruption in which each ectopic tooth changes the normal order of the tooth sequence in the dental arch.

1. Aetiology

The fundamental aetiology for dental transposition is genetic, within a model of multifactorial inheritance (Peck et al,1993&1998)

2. Prevalence

Transposition most often occurs at maxillary canine.

Peck and Peck (AJO 1995), reviewed maxillary tooth transpositions, and classified according to the most prevalent as

• 71% of the cases as maxillary canine – first premolar transposition

• 20% as canine – lateral incisor

• 4% as canine – first molar 

• 3% as central incisor and lateral incisor

• 2% as canine and central incisor transposition

According to Abu-Hussein and Watted (2015), prevalence in syndromic patients is significantly higher. Tooth transpositions are observed at a rate of 14.29% in patients with Down’s syndrome and at a rate of 4.1% in cleft palate patients. Also more frequent in women, in the maxilla, as a unilateral condition and in the left facial half.

According to Papadopoulos et al (AJO 2009), tooth transposition occurs more often unilaterally than bilaterally, with maxillary prevalence, and no sex preference. Tooth transposition is significantly unrelated to dental anomalies, such as congenitally missing teeth, peg-shaped or hypoplastic teeth, and impacted teeth. Although it may be associated with over-retained deciduous teeth, it is an isolated phenomenon rather than a syndrome.

Tooth transposition is often accompanied by several congenital dental disturbances such as severely rotated teeth and dilacerated teeth hypodontia (Peck et al., 1993 &1998; Plunkett et al., 1998; Shapira and Kuftinec, 2001) peg-shaped maxillary lateral incisor teeth (Peck et al., 1993 &1998; Plunkett et al., 1998; Shapira and Kuftinec, 2001 ) retained primary teeth (Shapira and Kuftinec, 2001) Down syndrome (Shapira et al, 2000) 

Maxillary occurrence of tooth transposition was found to be higher than the mandibular. The high bone density of the mandible might be responsible for a prohibition of the phenomenon of tooth transposition, and thus the higher incidence of maxillary occurrence. 

The most common type of tooth transposition in the mandible takes place between the canines and lateral incisors, also rarely with mandibular canine which is a transposition caused by the ectopic eruption of an impacted mandibular canine after transosseous transmission across the symphyseal midline. 

In mandible it is more common in the anterior where the bone is more porous than in the posterior area. In contrast, the lower density of bone in the maxilla may enhance the incidence of tooth transposition as well as the variety of types of transposition.

3. Classification

Three-part coding (Favot et al,1986) 

[For example, Mx C P1 means transposition of maxillary canine to first premolar position]
Transposition in permanent dentition, according to Peck et al, classified as:

Mx.C.P1

Mx.C.I2

Mx.I2.I1

Types of Transposition

• Complete: When the position of affected teeth is totally transposed i.e. when the crowns and the roots of the involved teeth exchange places in the dental arch.

• Incomplete (or pseudo or partial transposition): – When only the crowns are transposed, while the roots remain in normal position. 

Peck and Peck designated Mx for maxillary arch, and Papadopoulos et al used Mn for mandibular arch.

They denominated I1 for central incisor, I2 for lateral incisor, C for canine, P1 for the first premolar, P2 for the second premolar, and M1 for the first molar. This notation was deficient in defining the unilateral or bilateral nature of transposition, tooth location (facial/palatal), eruption status (impacted/partially erupted/fully erupted), and the quadrant of the transposed teeth.

To overcome this deficiency in classification system, a new Classification- notation system was proposed by Rai, et al. (JIOS 2016).

New Transposition Notation System

Numbers from 1 to 8 represent the tooth number from central incisor to third molars, respectively.

↑ Symbol will denote maxillary arch, like T↑

↓ Symbol will denote mandibular arch, like T↓.

Unilateral or bilateral transposition will be mentioned on the left or right or both sides of “T” in subscript. For example:

• Unilateral maxillary canine‑first premolar transposition of the right side, a notation will be ↑3F‑4P T
• Unilateral maxillary canine‑first premolar transposition of the left side, a notation will be T↑3F‑4P
• Bilateral maxillary canine‑first premolar transposition, a notation will be ↑3F‑4P T↑3F‑4P

If a tooth fully erupts, nothing is added in the superscript, with F or P. 

However, if a tooth is impacted or partially erupted, I or E is added in the superscript, respectively.

[Example: a case with bilateral maxillary canine‑first premolar transposition, in which left canine partially erupts and right canine is impacted palatally, a notation will be ↑3P, I‑4F T↑3F, E‑4P].

New Transposition Classification System

This new classification embraces two classes, i.e. Class I and II. 

Class I and Class II are further divided into three subtypes. 

These classes are organized according to the severity of transposition, and this aims to help in clinical diagnosis and treatment planning.

Class I/incomplete

Only one of the transposed teeth changes its position.
Seen only in cases with transposition of adjacent teeth

Canine-first premolar

Canine-lateral incisor

Class II/complete

Both the transposed teeth interchange their positions
Seen in cases with transposition of adjacent and non-adjacent teeth

Canine-first premolar

Canine-lateral incisor

4. Treatment Methods

The aims of orthodontic treatment are to restore the correct occlusion and provide favourable facial aesthetics, thus maintaining periodontal health, as well as health of tooth support structures.

Treatment options for these transposed teeth include;

• alignment of teeth in their transposed positions,
• correction of the teeth to their normal position, and
• extraction of one or both transposed teeth.
  
  

These options need to be evaluated as part of the overall treatment plan for each individual malocclusion by thorough intraoral examination followed by complete radiographic analysis and will often require fixed appliances.

Peck and Peck suggested that teeth with pseudo-transposition could be corrected into their normal positions.

 Moving complete transposed teeth to their normal positions is challenging because this requires bodily movement and translation of one tooth to pass another. This procedure may cause damage to the teeth and the supporting structures. Hence, in the case of complete transposition, alignment of the teeth in their transposed positions is often suggested; however, reshaping the crowns should be performed in order to achieve an acceptable aesthetic result.

Factors to be considered when making treatment plans for a transposed tooth include: 

• Dental morphology – Extraction is indicated when reshaping is difficult for a transposed tooth with strange crown morphology. 

• Occlusal considerations – The underlying malocclusion, both morphological and functional, and the possibility of obtaining canine-guided or group function occlusion influence the choice of treatment.

• Facial aesthetics – Facial profile is also important whenever extraction is taken as an alternative.

• Stage of root development and position of the root apices – The sufficiency of the buccolingual width of the supporting alveolar bone is an important aspect when moving two adjacent teeth in different directions. Compression and friction during correction can cause iatrogenic damage
  to the teeth (such as root resorption) and periodontal tissues (such as clefting and recession of gingival tissue).

• Shape of the root – The root shape of the tooth and the degree of root completion should also be examined to avoid fenestration especially in cases with root dilacerations. When replacing the canine with the first premolar, the roots of the maxillary first premolar must have proper morphology to allow for the necessary rotation without generating buccal root fenestrations.

• Treatment time – Treatment time necessary for correction or maintenance of transposition must be taken into account from the best cost-benefit standpoint.

The transposition can be unchanged for a few reasons, namely: potential for root resorption and gingival recession, as well as difficulty in controlling orthodontic mechanics. The root resorption is sometimes present before the treatment of the patients with impaction or transposition.

Following are the methods of correcting a transposed tooth:

• Interceptive treatment:When the condition is found at early stages, with patients being from six to eight years old, it is recommended that deciduous teeth be extracted. This procedure is aimed to guide transposed tooth eruption back to its normal position, while the space is kept with a lingual arch or a transpalatal arch. The approach is only possible with tipped teeth, with roots near the desired position. This is also known as pseudo transposition.
  
  The best time for intervention in maxillary canine transposition is when the cup tip of the maxillary canine tooth germ is positioned superior to the root of the first premolar, so that the first premolar can be tipped distally, thus correcting the transposition, and the permanent canine can be guided into its correct position.

• Alignment of teeth at transposed position:Recontouring of incisal or occlusal surfaces is necessary, thus reshaping affected teeth.
  

• Extraction of one or both transposed teeth followed by orthodontic correction: The procedure is recommended when transposed teeth present severe caries, have been subjected to trauma, present little periodontal support and insufficient arch length.

• Orthodontic correction of transposed teeth: This option is not clinically feasible for all cases. This is because factors such as age, occlusion, patient’s compliance, tooth inclination, initial root positioning and alveolar bone quality must be taken into account in order to move transposed teeth. This approach demands meticulous torque and direction of force control, so as to move the transposed teeth while preserving buccal bone cortex. It requires longer treatment time, increases the risk of root resorption and bone loss. 
  

In cases of canine transposed with premolar (Mx.C.P1) and canine with lateral incisor (Mx.C.I2), the treatment of choice has often been alignment of teeth in transposed position or extraction of one or both transposed teeth.
In cases of canine transposed with lateral incisor (Mx.C.I2), there are two major problems to be overcome:

• the ability the lateral incisor has to function as canine and 

• the ability to disguise the canine in the position of lateral incisor. 
  
  

The maxillary lateral incisor is not as favorable for canine guidance, since its root is usually thin and short.  Thus, group disocclusion might be recommended for non-extraction cases. Maxillary canine reshaping usually requires a combination of incisal tooth wear and composite resin or dental veneer placement.

Conclusion

Tooth transposition can be successfully corrected, provided that diagnosis and orthodontic planning be meticulously carried out and tooth movement be completely controlled. Biological limits should be respected, so as to prevent root resorption and periodontal support impairment. Tooth transposition treatment includes a multidisciplinary approach embracing Orthodontics, Periodontology and Cosmetic Dentistry which is necessary to achieve aesthetic results, function and stability.

References

REFERENCES

Mirian et al, Tooth transposition: a multidisciplinary approach, Dental Press J Orthod. 2018 Jan-Feb;23(1):97-107
Martyn T Cobourne, Handbook of ORTHODONTICS

N. J. ELY et al, Dental transposition as a disorder of genetic origin, European Journal of Orthodontics 28 (2006) 145–151

Nishat Kuttapa et al, Bilateral Maxillary canine-premolar transposition, J Ind Orthod Soc 2011;45(4):193-197

Nishimura et al, Orthodontic correction of a transposed maxillary canine and first premolar in the permanent dentition, Am J Orthod Dentofacial Orthop 2012;142:524-33

Pi-Huei Liu et al, Orthodontic treatment of a complete transposed impacted maxillary canine, Journal of Dental Sciences (2015) 10, 102-108

Peck et al, Mandibular lateral incisor –  canine transposition, concomitant dental anomalies, and genetic control, Angle Orthod 1998;68(5):455-466.

Peck et al, Maxillary canine – first premolar transposition, associated dental anomalies and genetic basis, Angle Orthod 1993, Vol 6, no 2.

Rai, et al.: Transposition revisited – New classification and notation system. J Indian Orthod Soc, 2016;50:228-33.

Shapira and Kuftlnec, Tooth transpositions – a review of the literature and treatment considerations, Angle Orthod 1998, Vol 59, No. 4

Sridhar Premkumar,Orthodontics – Prep Manual for Undergraduates,Third Edition

William. R. Profitt, Contemporary Orthodontics (6^th edition)

Watted N, Abu-Hussein M (2016) Dental Transposition of Mandibular Canine and Lateral Incisor. J Dent Probl Solut 3(1): 045-049.

Dr Geoff Hall