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Transmigration is a rare phenomenon seen almost exclusively in the mandibular canines. The aim of the present study is to review transmigration phenomenon.
Appropriate guidelines for a systematic review were followed. The time period selected for the present systematic review was 2001–2016. The studies were selected from various electronic databases on the basis of their title, study, design, keywords, and abstracts. A total of 150 citations were searched initially, and after proper screening, 59 relevant articles were included. Additional data was obtained by searching journals and reference lists.
The literature search shows that transmigration is more frequent in the mandible than maxilla. The etiology of the condition is obscure; however, multiple factors have been attributed to the condition. They are more readily recognized now with the advent of panoramic radiographs. Transmigration is a rare anomaly causing varied manifestations and requires an interdisciplinary approach for management.
Early diagnosis of impacted canines is mandatory for timely treatment to ensure facial harmony and improved function.
Intraosseous migration of unerupted teeth across the midline is a rare phenomenon known as dental transmigration. Ando et al. in 1964 coined the term transmigration. Transmigration was defined as a phenomenon of the movement of unerupted canine through the midline by Tarsitano et al. Impaction of maxillary canines is more prevalent, whereas transmigration is seen more commonly in the mandible.[3,4] Transmigrated canines may remain impacted and asymptomatic or they can cause pressure resorption of roots of adjacent teeth, pain and discomfort, and neuralgic symptoms to the patient. With the advent of panoramic radiographs, the transmigrated canines are more frequently detected than before.[5,6] Other methods such as lateral cephalograms, computed tomography (CT), and cone beam computed tomography (CBCT) can be used to accurately localize the impacted canines and to detect root resorption of the adjacent teeth.[7,8,9] Early diagnosis with timely orthodontic or surgical intervention can help the orthodontists preserve the canines, which play an important role, in both esthetics and function, in human dentition.
Maxillary canine impaction has an incidence in the range of 0.8–2.8%.[11,12,13,14] Mandibular canine impaction incidence is reported to be 20 times lower than that for maxillary canines. In general population, the incidence of mandibular canine impaction is 0.31%. Dental transmigration is almost exclusively reported in mandibular canines. The incidence for this phenomenon has been reported to be ranging from 0.8–3.6% to 0.1%.[3,16] Kara et al. studied the prevalence of transmigration of various mandibular teeth and reported an incidence of 0.079% for mandibular canines, 0.0017% transmigrant lateral teeth and 0.0026% transmigrant premolars.
Literature was searched from the MEDLINE database for relevant articles regarding transmigration published till 30 march 2016. Addditional data was obtained by searching journals and reference list as cited in Table 1. Transmigration has been described by Nodine in prehistoric skulls. Thoma was the first to describe the anomaly in living patients. Joshi and Shetty reported two cases of unilateral mandibular canine transmigration. Although unilateral transmigration is more common,[19,20,21,22,23,24,25,26,27,28,29] bilateral cases of transmigration have also been reported by many authors.[10,12,16,29,30,31] Peck reported transmigration in canines and second premolars. The cases reported showed a higher occurrence of transmigration in women with no difference in prevalence on both the sides.[32,33,34] Maxillary canine transmigration has also been reported which is even rare.[32,33,34] Tarsariya et al. reported transmigration of mandibular canines in four cases and highlighted the importance of panoramic radiographs. Gupta et al. reported cases showing varied clinicoradiological presentations of transmigrated canines. Díaz-Sánchez et al. and Anbiaee and Akbarian reported cases of unilateral and bilateral transmigrated canines. Idris Elhag and Idris Abdulghani reported a case of failure of eruption of multiple teeth with bilateral transmigration of mandibular canines. Other similar cases of transmigration of canines have been reported with varied manifestations.[40,41,42,43,44,45,46] This anomaly is most often asymptomatic and generally not recognized during routine intraoral clinical examination. Radiographic examination such as panoramic radiographs are essential for the detection of transmigrations.
Various theories describing the etiology of the process of transmigration have been proposed. Displacement of the dental lamina to an abnormal position in early life may result in abnormal eruptive path. Distant migration is possible in the developmental stage of the tooth apex due to rich blood circulation and active alveolar bone formation. In addition to these, other factors such as conical shape of the canine, congenitally missing lateral incisors, cystic lesions of the canine, prematurely lost or over retained deciduous teeth, tooth size arch length discrepancies, and pathological conditions can result in the diversion of canine from its line of eruption.
Mupparapu classified transmigrated mandibular canines into five types:
Type 1: Canine impacted mesioangularly across the midline, labial, or lingual to the anterior teeth with crown portion of tooth crossing the midline.
Type 2: Canine horizontally impacted near the inferior border of the mandible below the apices of the incisors.
Type 3: Canine erupted either mesial or distal to the opposite canine.
Type 4: Canine horizontally impacted near the inferior border of the mandible below the apices of the premolar or molar on the opposite side.
Type 5: Canine positioned vertically in the middle with the long axis of the tooth crossing the midline.
The incidence of these types varies with Type 1 (45.6%) being the most common, followed by Type 2 (20%), Type 4 (17%), Type 3 (14%), and Type 5 (1.5%).
The treatment options for unerupted transmigrated mandibular canines vary depending upon their location and biological conditions. They may involve surgical, orthodontic, and cosmetic dental treatment.[1,51]
Surgical extraction of the transmigrated teeth may be required if it is not possible to bring the tooth into alignment. This is especially recommended if the mandibular arch is crowded and requires therapeutic extractions. Watted et al. and Mesquita and Salgado reported cases wherein surgical removal of transmigrated lower canine followed by space closure was recommended. Surgical extraction of transmigrated canines has been described as an option when the prognosis of such teeth is not good.
If the mandibular incisors are in a normal position and space for the transmigrated canine is sufficient, transplantation may be undertaken. Kulkarni and Lee and Verma reported cases of transmigrated mandibular canine managed with transplantation.
It may be possible to surgically expose and align the teeth in the dental arch when they are vertically aligned, as in the Type 5 cases, if the treatment planning dictates it. Watted et al. reported a case with mesioangular transmigration of 43 with odontoma in the region of 83. Treatment involved surgical removal of the odontoma followed by orthodontic alignment of 43 in the arch.
An unerupted impacted tooth may be removed as soon as convenient. However, if the tooth is symptomless, it can be left in place. In these patients, a series of successive radiographs should be obtained periodically.
Sinko et al. described a decision-making flowchart with surgical strategies for the management of impacted lower canines depending on some key aspects such as associated pathology, patient age, compliance, and root tip position.
A 16-year-old male patient presented to the outpatient department (OPD) with a chief complaint of irregularly placed upper front teeth. Intraoral examination showed all the permanent teeth till 2nd molars erupted in the oral cavity except 33 (lower left permanent canine) and retained 73 (lower left deciduous canine). Both upper and lower arches were crowded with discordant faciomandibular midline and discordant maxillomandibular midlines. Molar relation on both the right and left side was end on, and there was increased overjet and ovebite. Orthopantomogram of the patient showed Type 1 transmigration of impacted 33 [Figure 1]. Patient was informed about the condition and advised fixed orthodontic treatment. Treatment plan included orthodontic extractions of 14 and 24 in the upper arch and removal of the transmigrated canine and 73 in the lower arch to achieve the basic objectives of alignment and the correction of overjet, overbite, and molar relation.
A 19-year-old female patient presented to the OPD with a chief complaint of irregularly placed upper and lower front teeth. Intraoral examination showed retained 53 and 83 and missing 13 and 43. Faciomaxillary and faciomandibular and maxillomandibular midlines were discordant. Molar relationship on both sides was Class II with increased overjet and ovebite. Orthopantomogram of the patient showed impacted 13 and Type 2 transmigration of 43 [Figure 2]. Patient was informed about the condition and advised fixed orthodontic treatment. The treatment plan included the removal of the transmigrated canine and 83 in the lower arch and removal of 53 in the upper arch. It was planned to surgically expose 13 and bring it into alignment orthodontically. The case can be reviewed after this stage.
A 17-year-old male patient presented to the OPD with a chief complaint of irregularly placed upper and lower front teeth. Intraoral examination showed retained 71, 81, and 83 and missing 22, 31, 41, and 43. Faciomaxillary and faciomandibular and maxillomandibular midlines were discordant. Molar relationship on both sides was Class I with increased overbite. Orthopantomogram of the patient showed missing 31 and 41 and Type 5 transmigration of 43 [Figure 3]. Patient was informed about the condition and advised fixed orthodontic treatment. The treatment plan was to start with nonextraction fixed orthodontic treatment to achieve levelling and alignment in the upper arch followed by creating space for the replacement of 22. In the lower arch, extraction of 71 and 81 was planned followed by the eruption of 43 in place of 71 and 81 facilitated by orthodontic treatment. This can be followed by reshaping of 43.
Canines are considered to be the cornerstones of the dental arch. They play an essential role in maintaining the facial harmony and functional efficiency. The unerupted or transmigratory canines are generally asymptomatic. Radiographic examination is essential to diagnose impacted canines and panoramic radiographs are generally required to diagnose transmigrated canines. Timely detection and treatment can help to preserve these canines, surrounding tissues and dentition, resulting in better esthetic and function.
There are no conflicts of interest.