Transmigration of Mandibular Canines: A Report of Six Cases and a Review of the Literature
Background: The transmigration of a mandibular canine is a rare phenomenon, the etiology of which is not clear. The literature on this rare condition is reviewed, and six cases of transmigrated mandibular canines are presented.
Report: Panoramic radiographic examination of six patients revealed each patient had one impacted transmigrated mandibular canine. Of the six impacted teeth, the left mandibular canine was involved in four instances and the right in two. In one case the transmigrated canine was associated with a dentigerous cyst.
Summary: Transmigration of the mandibular canine is a rare event, and early radiographic examination of the patient is important for treatment. In addition, future studies may lead to a better understanding of this rare anomaly and improvement of the classification criteria.
Keywords: Canines, transmigration, tooth impaction, tooth migration
Citation: Sumer A, Sumer M, Ozden B, Otan F. Transmigration of Mandibular Canines: A Report of Six Cases and a Review of the Literature. J Contemp Dent Pract 2007 March;(8)3:104-110.
Transmigration is the movement of an impacted tooth through the midline. The movement of an unerupted tooth across the dental midline is unusual and worthy of investigation. Mandibular canines are rarely found in a horizontal position in the mandible, and their transmigration is a very rare phenomenon.1-2 According to Javid,3 an impacted mandibular canine that has crossed the midline more than half of its length should be considered as transmigrated. However, Joshi1 felt the tendency of a canine to cross the barrier of the mandibular midline suture is a more important consideration than the distance of migration after crossing the midline.
Impacted teeth are important in dentistry and are particularly significant in orthodontics, especially if the impacted tooth is a canine. The occurrence of impacted mandibular canines is more rare than maxillary canines, and it is an even more rare phenomenon when such an impacted mandibular canine migrates to the other side of the mandible, crossing the mandibular midline.1 The purpose of this article is to report six cases of transmigrated mandibular canines and to review the literature.
A 28-year-old man complained about the
appeareance of his retained mandibular right and left primary canines. Radiographic examination
revealed both mandibular permanent canines to be impacted. Although the right mandibular canine was unerupted it was in a favorable position. The unerupted left mandibular canine crossed the midline and transmigrated to the right side (Figure1).
A 22-year-old woman was referred to the oral surgeon for removal of impacted maxillary third molars. The panoramic radiograph revealed the left mandibular canine was impacted horizontally and its root crossed the midline (Figure 2).
A 54-year-old man was referred for construction of prosthesis. The panoramic radiograph indicated the mandibular right canine was impacted mesioangularly with part of the crown crossing the midline. The crown of this canine was surrounded by a dentigerous cyst (Figure 3).
A 14-year-old boy was referred for his retained mandibular left primary canine. The panoramic radiograph indicated the mandibular left canine was impacted between the central and lateral incisors. The mandibular central incisor was forced mesially with the midline shifted to the right side of the mandible. In addition, a dilaceration of the lateral incisor root was observed as a result of the left impacted canine (Figure 4).
Figure 1. Case 1: The mandibular right canine is in a favorable position and the left canine has crossed the midline.
Figure 2. Case 2: The mandibular left canine is lying horizontally and its root has crossed the midline.
Figure 3. Case 3: The mandibular right canine is in a mesioangular position with part of the crown crossing the midline and surrounded by a dentigerous cyst.
Figure 4. Case 4: The mandibular left canine is impacted between the central and lateral incisors forcing the central incisor mesially and shifting the midline to the right side of the mandible.
A 23-year-old woman was referred for periodontal treatment. Radiographic examination revealed a horizontally impacted right canine tooth migrated across the midline located below the apices of premolar teeth within the mandible (Figure 5).
A 13-year-old boy was referred for evaluation of his retained mandibular left primary canine.
Panoramic examination revealed a horizontally impacted left mandibular canine tooth had migrated across the midline located below the apices of the incisors (Figure 6).
Migration of mandibular canines across the midline is referred to as ‘transmigration.’ This is a rare phenomenon as described in a review of the literature1-54 which reported only 154 cases (Table1). Most of the subsequent reports have described single cases. Transmigration of an unerupted tooth is generally a unilateral phenomenon, although 16 cases of bilateral transmigration have been reported.1,52 Joshi1 observed four cases of bilateral transmigration among a collection of 28 cases. The left canine is more involved than the right canine.1,51In four of six patients in the present report the left canines
Figure 5. Case 5: A horizontally impacted mandibular right canine located below the apices of left premolar teeth that crossed the midline.
Figure 6. Case 6: Horizontally impacted mandibular left canine crossing the midline located below the apices of the incisors.
Table 1. Chronological listing of transmigratory mandibular canines observed by different authors.
were involved. The incidence of transmigrated canines is much higher in females than in males. In the literature, transmigrated canines have been reported in 87 females and 57 males.
Gender was not mentioned in ten of the cases.
A specific etiology of this anomaly is not known, but traumatic factors, heredity, the long erruption path of canine tooth germs, premature loss of primary teeth, filling of this space by an adjacent tooth, disharmony of tooth-size, unfavorable alveolar arch length, and over length of crowns can be the causative factors.1,51,53 Odontomas are also suggested as a possible etiological factor.30 A permanent canine within a dentigerous cyst may transmigrate due to the cystic pressure. In one of the present patients, the transmigrated canine was associated with a dentigerous cyst.
However, it may not be possible to determine whether the tooth was transmigrated before the pathological process developed or not.
Mupparapu52 used five criteria to classify the transmigrated canines. These are summarized as follows:
• Type 1: The canine is impacted
mesioangulary across the midline, labial, or lingual to the anterior teeth with the crown portion of the tooth crossing the midline.
• Type 2: The canine is horizontally impacted near the inferior border of the mandible below the apices of the incisors.
• Type 3: The canine has erupted either mesial or distal to the opposite canine.
• Type 4: The canine is horizontally impacted near the inferior border of the mandible
below the apices of either premolars or molars on the opposite side.
• Type 5: The canine is positioned vertically in the midline with the long axis of the tooth crossing the midline.
Most of the cases reported in the literature are Type 1.52 Of the six cases in the present report, two canines exhibited a Type 1 transmigratory pattern, two canines exhibited Type 2, and one each of Types 4 and 5. In the present study, one canine was impacted horizontally below the apices of the insisors with the root portion of the tooth crossing the midline (Type 2) which was contrary to the majority of Type 2 transmigrated canines that have the crown portion of the tooth crossing the midline.
Howard1expected the older patient would show a greater distance of travel because a longer time had been available for the migratory canine to travel. Ando and coworkers9 observed transmigration in their patient for six years.
During this time, the canine moved from its original position to a place near the mental foramen on the opposite side. Out of five cases according to Al-Waheidi,50one case exhibited mandibular canines in a favorable position while two and half years later these teeth were found to be mesially inclined, and the unerupted mandibular left canine had crossed the midline.
These cases emphasized the importance of early radiographic examination of these patients.
In the present study the average patient age was 32 except for cases four and six. In these patients obtaining a panoramic radiograph before F: Females; M: Males; NA: Not Available
Table 1. Continued
treatment may reveal impacted mandibular canines in a favorable position and make the treatment more effective and less complicated.
Once the transmigration process is definitely established, the only treatment possible is surgical extraction.1
Transmigration of the mandibular canine is a rare event, and early radiographic examination of a patient is important for treatment planning.
Future studies may lead to a better understanding of this rare anomaly and improvement of the classification criteria.
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