failure of the tooth to erupt into the dental arch , usually due to either space deficiency or presence of an entity blocking its path of eruption results in impaction . an impacted tooth occasionally migrates to a location some distance away from the site in which it develops but usually remains within the same side of the arch . when such a tooth crosses the midline , this rare phenomenon is known as dental transmigration . the term transmigration was first used by ando et al . as it appears to be the most appropriate of all terms since canine migrates from one side of the jaw to the other side crossing the midline . according to javid : an impacted mandibular canine that has crossed the midline more than half of the length should be considered as transmigrated . it is believed that transmigration is unique to the mandibular permanent canine , and even more rarely reported for others . migration may occur as a result of localized pathological process , such as cystic lesion or an odontoma . the path of least resistance probably determines the direction of movement of the migrating tooth . it follows the direction of its long axis , with the crown leading the migration . we are presenting a case of 22-year - old female patient who reported to the department of oral and maxillofacial surgery which was referred from the department of orthodontia with the impacted right mandibular canine in an aberrant position [ figures 1 ] . the type of this canine according to the classification is type 2 with the angulation of 90 which was detected accidently on a panoramic radiograph . the tooth was lying horizontally at the inferior border of the mandible below the apices of the lower incisors . orthopantomogram of patient showing transmigrated mandibular canine under strict aseptic conditions patient was painted with povidone iodine and draped . incision was extended from right premolar to left premolar and two releasing incisions were given in the vestibule bilaterally . bone cutting was done using a number 8 stainless steel round bur ; a window was made which was more widened by cutting the buccal cortical plate . impacted teeth are very important in oral and maxillofacial surgery and are particularly significant in case of canine as the impaction of mandibular canine is 20 times rarer than that of maxillary canine and it is even more rare when such an impacted canine migrates to other side of the mandible crossing the midline . failure of eruption of mandibular canine is an unusual event and is worthy of investigation . in the classic transmigratory pattern , mupparapu proposed classification for transmigrated teeth and he classified these teeth into five types based on their migratory pattern and their position in jaw . mandibular left canine was found to be affected more than the right one and in our case we have right side canine involvement . the reported ratio is 1.6:1 and in our case we also have a female patient . although a number of factors have been suggested with regard to transmigration , the etiology and exact mechanism is still unclear . nodine reported that it is not possible to put forward a definite etiological factor responsible for this anomaly . some other factors are : retention or premature loss of primary teeth , crowding , spacing , supernumerary teeth and an excessive crown length of mandibular canine . nodine reported that impacted and migrated mandibular canines often do not produce any apparent symptoms and ando et al . , did not observe symptoms such as oppression of the mandibular nerve due to transmigration of canine . in our case we also did not observe any kind of symptoms which could reveal the presence of a migrated canine . those impacted canines that were between 30 and 95 are a group that tends to cross the midline . an overlap appears to exist between 30 and 50. when this angle exceeds 50 , crossing the midline becomes a rule . considering this rule , the migratory canine in the present paper is at 90. shapira and kuftinec stated that this abnormality was usually accompanied by a cyst or odontoma . joshi stated that it was difficult to differentiate whether these pathological conditions were responsible for transmigratory process or vice - versa , happened . in the case treatment of choice , can be orthodontic repositioning , surgical extraction of the aberrantly placed canine , transplantation and surgical exposure with orthodontic alignment . we chose surgical extraction of the transmigratory canine as the best treatment of choice . in conclusion , further documentation of this anomaly may lead to its inclusion as one of the developmental anomalies of teeth .
pre - eruptive migration of a tooth across the midline is termed as transmigration . 
 it is believed that transmigration is rare and unique to the mandibular permanent canines , and even more rarely reported for others . 
 transmigration is a phenomenon of yet unknown etiology . 
 it follows the direction of its long axis , with the crown leading the migration . 
 the tendency of a canine to cross the barrier of mandibular midline suture is a more important consideration than the distance of migration after crossing the midline . here 
 we present one new case of aberrantly positioned right mandibular canine which has undergone migration and was accidently found on radiological examination before orthodontic treatment . 
 once diagnosed an aberrantly positioned impacted canine requires surgical removal .