Treatment and Long Term Follow-Up of a Patient with an Impacted Transmigrant Canine

Impacted teeth are those with a delayed eruption time or those which are not expected to erupt completely based on clinical and radiographic assessment (Richardson & Russell, 2000). All teeth can be impacted. However, third molars, maxillary canines, maxillary and mandibular premolars, and maxillary central incisors are the teeth most frequently involved (Rajic et al., 1996). Impactions are twice as common in females (1.17 %) as in males (0.51 %). The prevalence of impacted maxillary canines is 0.9–2.2%, but mandibular canine impaction occurs 20 times less frequently than maxillary canines (Alaejos-Algarra et al., 1998; Aydin et al., 2004; D’Amico et al., 2003). 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 (Joshi, 2001). Shah et al. (1978) found 8 unerupted mandibular canines in 7886 individuals. Grover and Lorton (1985) found 11 impacted mandibular canines in 5000 individuals. Ericson and Kural (1986) estimated the incidance of mandibular canine impaction to be 0.35 %. The etiology of impacted teeth is unknown, though several mechanisms have been proposed. Tumors, cysts, and odontomes may cause malposition of teeth if they lie in the path of eruption of teeth. Other possible etiologic factors suggested by some authors are premature loss of deciduous teeth, prolonged retention or early loss of the deciduous canine, crowding, spacing, supernumerary teeth, abnormal position of the tooth bud, excessive length of the crown of the mandibular canines, dilaceration of the root, iatrogenic origin and idiopathic condition with no apparent cause cystic lesions, an abnormally strong eruption force and heredity (Bishara, 1992; Javid, 1985; Joshi & Shetye, 1994). The treatment options for impacted canines are no treatment, surgical intervention, removal, transplantation, prosthetic or restorative treatment or surgical exposure with or without orthodontic traction to align the malpositioned tooth. The preferred option is surgical exposure and alignment (Blair et al.,1998). Successful treatment of impacted canines is dependent on the position of the tooth in both the sagittal and transversal planes, ankylosis and dilaceration of the tooth. It has generally been accepted that the more a canine is horizontally impacted, the less successfull the tooth will be brought into its correct position (Odegaard, 1997). Since prevention of impacted canines provides the best long-term results, intervention with surgical attachment of an orthodontic button or bracket should be implemented only as a second alternative (Crawford, 2000).


Introduction
Impacted teeth are those with a delayed eruption time or those which are not expected to erupt completely based on clinical and radiographic assessment (Richardson & Russell, 2000).All teeth can be impacted.However, third molars, maxillary canines, maxillary and mandibular premolars, and maxillary central incisors are the teeth most frequently involved (Rajic et al., 1996).Impactions are twice as common in females (1.17 %) as in males (0.51 %).The prevalence of impacted maxillary canines is 0.9-2.2%,but mandibular canine impaction occurs 20 times less frequently than maxillary canines (Alaejos-Algarra et al., 1998;Aydin et al., 2004;D'Amico et al., 2003).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 (Joshi, 2001).Shah et al. (1978) found 8 unerupted mandibular canines in 7886 individuals.Grover and Lorton (1985) found 11 impacted mandibular canines in 5000 individuals.Ericson and Kural (1986) estimated the incidance of mandibular canine impaction to be 0.35 %.The etiology of impacted teeth is unknown, though several mechanisms have been proposed.Tumors, cysts, and odontomes may cause malposition of teeth if they lie in the path of eruption of teeth.Other possible etiologic factors suggested by some authors are premature loss of deciduous teeth, prolonged retention or early loss of the deciduous canine, crowding, spacing, supernumerary teeth, abnormal position of the tooth bud, excessive length of the crown of the mandibular canines, dilaceration of the root, iatrogenic origin and idiopathic condition with no apparent cause cystic lesions, an abnormally strong eruption force and heredity (Bishara, 1992;Javid, 1985;Joshi & Shetye, 1994).The treatment options for impacted canines are no treatment, surgical intervention, removal, transplantation, prosthetic or restorative treatment or surgical exposure with or without orthodontic traction to align the malpositioned tooth.The preferred option is surgical exposure and alignment (Blair et al.,1998).Successful treatment of impacted canines is dependent on the position of the tooth in both the sagittal and transversal planes, ankylosis and dilaceration of the tooth.It has generally been accepted that the more a canine is horizontally impacted, the less successfull the tooth will be brought into its correct position (Odegaard, 1997).Since prevention of impacted canines provides the best long-term results, intervention with surgical attachment of an orthodontic button or bracket should be implemented only as a second alternative (Crawford, 2000).
Transmigration was defined as a phenomenon of an unerupted mandibular canine crossing the mandibular midline (Tarsitino et al., 1971).Later Javid (1985) stated that the midline was required to be crossed by one-half or more of the length of the tooth.However in 2006, Auluck et al., suggested that 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.Until recently most studies have reported that the mandibular canine is the only tooth in the dental arch that migrated across the midline.Yet recently, Kara et al. (2011) have encountered two transmigrant laterals and three transmigrant premolars in 90 transmigrant teeth.In other studies, transmigration of a lateral incisor (Camilleri, 2007), a premolar (Alves et al., 2008) and maxillary canines (Aydin & Yilmaz, 2003;Shapira & Kuftinec, 2005) have been detected.Different incidences have been reported in the rate of transmigrant teeth.Zvolanek (1986) failed to find any cases in a sample of 4,000 patient series.Javid (1985) reported that a radiographic survey of 1000 students revealed only 1 transmigrated impacted mandibular canine.In the studies considering the Turkish population, Aydın et al. ( 2004) observed 0.31%; Aktan et al. (2010) found 0.34%; Büyükkurt et al. reported (2007) 0.33 ratio of transmigration and recently Kara et al. (2011) found 0.075 percentages of transmigrant teeth.Joshi (2001) stated that 89 % of the transmigratory mandibular canines were impacted and 91 % were unilateral.The left canine is more involved than the right canine, and women tend to have this condition more frequently than do men (Joshi, 2001;Kara et al., 2011).Although unilateral migration is more common, bilateral transmigration of mandibular canines has also been reported (Kuftinec et al., 1995).Transmigrant teeth may erupt ectopically at the midline or on the opposite side of the arch (Camilleri & Scerri, 2003).The transmigrated teeth maintain their nerve supply from the original side (Fiedler & Alling, 1968).Stafne (1963) reported that a transmigrated mandibular canine always moves in the direction of the cusp tip and deviates mesially.The transmigrant canine usually travels along the labial side of the incisor roots and migrates as far as the roots of the first molar on the opposite side (Camilleri & Scerri, 2003;Javid, 1985). .Ando et al. (1964) and Stafne (1963) stated that movement of transmigratory canine is more rapid before the formation of its root, yet Dhooria et al. (1986) observed a fairly rapid movement even after completion of the root formation.The exact mechanism of transmigration is not yet known although numerous theories exist in the literature to explain their occurrence.One of the theory is that the transmigrant teeth could be the result of a malpositioning of the dental lamina during the embryonic stage of tooth development (Joshi, 2001).Heredity has been hinted as a causative factor.Most of the time, the canine just migrates without any pathological entity, but rarely a cyst or odontoma accompanies such a tooth (Kara et al., 2011).Clinical and radiographic examination is usually required to diagnose transmigrant teeth for they are usually detected within the symphysis of the mandible.In the existence of overretention of the primary canine, a radiographic examination should have be done to check the permanent mandibular canines.(Joshi & Bhatt, 1971).When a transmigrant mandibular canine reaches a horizontal position where there is no obstruction by the roots of the incisors, it may travel forward toward the midline, cross the symphysis and assume a position where the entire tooth may be situated on the opposite side of the mandible (Stafne, 1963).Thoma (1963) states that horizontally impacted transmigrated canine "almost always have to be removed".The aim of this case report is to demonstrate that a horizontally transmigrated mandibular canine can be treated by using surgical exposure and orthodontic treatment mechanics and to show the long-term results.

Case report
The patient was a 10 year 1 month-old white female when she first applied for an orthodontic consultation.The medical history revealed no medical problems.There was no history of trauma to the craniofacial complex.She was in the early mixed dentition and complete orthodontic records were obtained.In clinical investigation, a crossbite in upper left region and Angle Class III malocclusion were observed.Panoramic and cephalometric radiograph analysis revealed a horizontally impacted mandibular right canine with its crown located slightly distal to the right central incisor root apex (Figure 1,2,3,4).A maxillary Schwarz appliance was used to correct the posterior crossbite.In the retention period of the Schwarz appliance, a panaromic radiograph of the patient was taken.According to the panaromic radiograph, it was observed that the horizontally right impacted canine migrated mesially, crossed the midline and became a transmigrant tooth (Figure 5).

Treatment plan
Treatment options were surgical removal, surgical exposure and orthodontic traction or autotransplantation of the impacted tooth.We didn't prefer the autotransplantation option since the root of the tooth was already completed.All of the treatment alternatives were explained to the patient and her parents.They accepted the surgical exposure and orthodontic traction option.If orthodontic traction had not been successful, the impacted tooth would have been extracted and implant or prothetic approaches could have been performed.

Treatment progress and results
First, the patient was referred to an oral surgeon for the elimination of follicule epithelium.Three weeks later, an open approach was performed and a window was opened on the mucosa through cauterization, then an orthodontic bracket with 0.30 mm.ligature wire extending into the oral cavity was surgically attached to the canine (Figure 6).Two weeks later, 50 gr orthodontic force was applied to transmigrated canine through elastics hanged between Schwartz appliance and the canine (Figure 7).This application continued for 9 months.At the end of 9 months, a new appliance was done and the traction force was increased to 90 grams.After one year, the crown of the transmigrant canine was seen intraorally (Figure 8,9,10).Comprehensive orthodontic records were secured, and it was decided to attempt a nonextraction mode of treatment, with 0.018'' x 0.022'' slot Roth appliances.In the aligning period of the mandibular arch, 0.014'' and 0.016'' NiTi was used with an open coil spring which was placed between 42 and 44 to create space for the transmigratory tooth.After providing adequate space, 0.016'' SS arch wire with stopper bends was applied to the mandibular arch.An intra-mandibular elastic applying 90 grams force was hanged between 43 and 46 for the distalization of 43.Then 44,45,46 and 41,42,31,32,33 were figurated to strengthen their anchorage.An extrusive force was applied to 43 by a chain elastic hanged between 44 and 42.Meanwhile 0.014'' and 0.016'' NiTi arch wires were applied for the alignment of the maxillary arch.Then 0.016'' x 0.022'' NiTi, 0.017''x 0.022'' Ni-Ti and SS arch wires were applied respectively to maxillary and mandibulary arches to maintain torque.The fixed orthodontic treatment elapsed 2 years.Class I molar and canine relationship bilaterally were achieved.The arches were successfully aligned and leveled, and ideal overbite and overjet were established.Comprehensive orthodontic records were obtained and Hawley appliances were prepared for retention (Figure 11,12,13).Superimposition and cephalometric analysis of the patient before and after orthodontic treatment are shown in Figure 14 and Table 1.The Hawley appliances were used for 8 months all day and the following 8 months only at night.

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Three years later from retention which is in fact four and a half years later from fixed orthodontic treatment, the patient was recalled to check the stability of the treatment and the position of third molars.Full orthodontic records were obtained (Figure 15,16).The patient was referred to oral surgeon for the removal of 18, 28 and 48 to provide the occlusion stability.The retention records demonstrated good results.

Discussion
Transmigration of the mandibular canine across the mandibular midline is a rare and elusive phenomenon.Mupparapu (2002) described five patterns of canine transmigration: Type 1 for a canine impacted mesio-angularly across the midline, labial or lingual to the anterior teeth; Type 2 for a canine horizontally impacted near the inferior border of the mandible inferior to the apices of the incisors; Type 3 for a canine erupting on the opposite side of the jaw; Type 4 for a canine horizontally impacted near the inferior border of the contralateral side and Type 5 regardless of eruption status, canine positioned vertically in the midline with the long axis of the tooth crossing the midline.Type 2 corresponds to our case.According to Mupparapu (2002), the most frequently encountered type of transmigrant teeth was type 1, followed by type 2 and then type 4. Type 5 was the least frequently seen.
Impacted and transmigrated mandibular canines are often symptomless.Patients in deciduous dentition demonstrating the absence of the permanent canine from the mandibular arch, may be suspected to have an impacted or transmigrated canine (McDonald & Yap,1986).
Treatment considerations for transmigratory teeth depend on the stage of development, distance of migration and the symptoms.When the root apices are closed, extraction often is the only choice.Clinical clues can help to diagnose this problem at an early stage to avoid extraction.Axial inclination of the canines can help to predict the likelihood of canine impaction and transmigration (Joshi, 2001).Canines lying within 25 º to 30 º of the midsagittal plane have a tendency for impaction, but they do not migrate to the midline.If canines are within an angle of 30 º to 50 º, they tend to cross the midline yet those that are found at an angle greater than 50 º, transmigration is almost always the rule (Pratt, 1969).Stafne (1963) found that the greatest amount of tooth migration occurred before the root is completely formed.If these malpositioned teeth can be detected early, they may be surgically exposed and moved using orthodontic forces.The other treatment options proposed for impacted mandibular canines include observation, surgical removal and transplantation (McDonald & Yap, 1986).
If the impacted teeth is asymptomatic, it can be left in its place, but a series of radiographs should be taken periodically (Plumpton, 1966).Surgical extraction could be planned in the following situations (Camilleri & Scerri, 2003): 1. Progressive deterioration of the position of the mandibular canine during a one year follow-up period.2. If the patient has any associated abnormalities, such as a developing apical cyst, neuralgia, displacement of teeth or resorption of an adjacent tooth root.3. Severe mandibular crowding which requires therapeutic extractions to correct the incisor crowding.This would reduce the orthodontic treatment time and also the hazardous orthodontic tooth movement.Wertz (1994) advocated that, if a nonextraction method of orthodontic treatment is indicated, a surgical repositioning should probably be attempted just before extracting the transmigrated canine.However, if the diagnosis indicates an extraction mode of treatment in the lower arch, then the transmigrated canine should be extracted instead of the usual premolar, eliminating excessive treatment time.Howard (1976) expressed a similar viewpoint.If adequate space for alignment of an impacted mandibular canine exists and it is mechanically possible to reposition an impacted mandibular canine into proper position, then surgical exposure and orthodontic treatment is indicated (Ferguson, 1990;McDonald & Yap, 1986).In published reports, tranmigrant canines were treated mostly by surgical extraction (Gonzalez-Sanchez, 2007).Only Wertz (1994) reported three transmigrant canines corrected successfully by surgical exposure and orthodontic treatment.Wertz (1994) reported that, if the tip of the crown has migrated past the opposite incisor area or if the apex has migrated past the apex of the adjacent lateral incisor root apex, it might be mechanically impossible to bring the aberrant canine into its normal place.Autotransplantation is another approach to correct this problem.Camilleri and Scerri (2003) stated that when the mandibular incisors are in a normal position and space for transmigrated canine is sufficient, autotransplantation may be undertaken.However, an immature tooth is required for success, and the difficulty in removing the tooth in one piece complicates the procedure (Rebellato & Schabel, 2003).In this case, the root development of the transmigrated mandibular canine was already completed.Therefore, surgical exposure and orthodontic traction was preffered instead of autotransplantation.Some authors believe that the age of patient is an important factor in the success of proposed tooth movement (Machen, 1989).In patients under 14 years old, before extracting the tooth, other options should be considered and the case should be carefully assessed.In patients over 14 years old, significant changes are not expected and extraction should only be considered (Ando et al., 1964).In a recent retrospective study, Aras et al. (2011) reported that forced eruption in four teeth out of twenty mandibular impacted canine teeth applying a traction force resulted in failure.They claimed that high mean age could be the reason of failure.Orton et al. (1995) states that treatments starting after the end of a pubertal growth spurt are likely to be protracted.In this case, successful forced eruption of the transmigrated canine may also be due to the orthodontic treatment of the case at an early age.Experimental studies have shown that the loss of periodontal attachment does not occur during orthodontic tooth movement providing the periodontium is maintained in a healthy state (Ericsson & Thilander, 1978).However, in clinical studies, the variable loss of periodontal support is observed which may reflect the hygiene challenge associated with fixed orthodontic appliances (Alstad & Zachrisson, 1979;Zachrisson & Alnaes, 1973).Except this condition, various periodontal problems can occur due to the surgical approach.Either an open or a closed surgical approach can be used to uncover the crown of impacted tooth and to place an orthodontic attachment.Open approach may lead to gingival recession, bone loss, decreased width of keratinized gingiva, delayed periodontal healing and gingival inflammation.With close approach method, less complications and more esthetically pleasing results are obtained (Frank & Long, 2002).In this case, open approach was performed to uncover the crown of the impacted tooth because of the localization of the tooth and the direction of the orthodontic forces that would be applied.In the long term, no periodontal complications except mild gingival recession was detected.No root resorption or pulpal damage was observed in both the transmigrated canine and the adjacent teeth.An ideal Class I occlusion was maintained at the end of the treatment.The results were satisfying and stable 4.5 years after from the fixed orthodontic treatment.

Conclusion
This case demonstrated that a horizontally impacted transmigrant mandibular canine can be succesfully treated without the risk of root resorption, periodontal and pulpal damage by maintaining adequate plaque control, applying small and constant forces and preferring the appropriate surgical approach.

Fig. 5 .
Fig. 5. Panaromic radiograph of patient at the retention period of Schwarz appliance.

Fig. 6 .
Fig. 6.Panaromic radiograph of patient showing surgically attached of an orthodontic attachment to the canine.