JADA Continuing Education
Transmigrant impacted mandibular canines
A retrospective study of 15 cases
Miguel Angel González-Sánchez, DDS,
Leonardo Berini-Aytés, MD, DDS, PhD and
Cosme Gay-Escoda, MD, DDS, PhD
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ABSTRACT
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Background. Transmigration of mandibular canines across the midline is rare. The authors describe the clinical and radiologic characteristics of patients with transmigrant impacted mandibular canines.
Methods. The authors conducted a retrospective observational study of 14 patients with transmigrant canines. They diagnosed transmigrant canines in all of the patients on the basis of the clinical and radiological findings, and they obtained the data from the patients’ case histories and panoramic radiographs. They considered a canine to be transmigrant when one-half or more of its length crossed the mandibular midline.
Results. There were 15 transmigrated canines in 14 patients aged 16 to 60 years. Primary canines were present in 10 cases. One case involved a pericoronal infection, two involved supernumerary teeth, one was associated with an odontoma, and in two a pericoronal radiolucency was seen that was compatible with a follicular cyst. Treatment consisted of surgical extraction for eight patients, and periodic clinical and radiologic follow-up visits for six patients.
Conclusions. Radiographic examination is necessary to diagnose impacted transmigrant canines, among other anomalies. Surgical extraction is the treatment of choice for patients with transmigrant canines involving associated pathology. In some cases, the management of asymptomatic impaction can be limited to periodic clinical and follow-up visits.
Clinical Implications. The absence of the permanent canine within the arch beyond the normal time of eruption suggests the presence of an impacted canine. A transmigrant canine may develop an associated pathology.
Key Words: Transmigrated canine; tooth migration; impacted canine
Impacted permanent canines are relatively common and have been documented extensively in the literature. Mandibular canine impaction occurs approximately 20 times less frequently than maxillary canine impaction.1 In the general population, the incidence of mandibular canine impaction ranges from 0.35 to 0.44 percent.1,2 An even less common finding is the migration of a mandibular canine from its normal position to the contralateral hemiarch, crossing the midline. This phenomenon is known as transmigration, and it occurs almost exclusively with mandibular canines; only two published reports have described maxillary canine migration to the contralateral side.1,3
In 1971, Tarsitano and colleagues4 defined transmigration as a phenomenon in which an unerupted mandibular canine migrates, crossing the mandibular midline. In 1985, Javid5 modified Tarsitano and colleagues’ definition, adding that one-half or more of the length of the tooth was required to cross the midline. In 2006, Auluck and colleagues6 suggested that the actual distance of canine migration across the mandibular midline is less important than the tendency of the canine to cross the midline.
In this article, we describe the clinical and radiologic characteristics of patients with transmigrant impacted mandibular canines seen in an oral surgery service. We also conducted a literature review.
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SUBJECTS AND METHODS
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We conducted a retrospective study of 14 patients (eight male and six female) with a mean age of 31.9 years (range, 16–60 years). All 14 patients had transmigrant mandibular canines that we diagnosed by using panoramic radiograph (12 patients by using conventional panoramic radiography and two patients by using digital panoramic radiography) and were referred to our oral surgery and implantology clinic at the University of Barcelona Dental School in Spain between 1991 and 2005. We obtained demographic data from the patients’ case histories at the time their transmigrant impacted canines were diagnosed.
We considered a canine to be transmigrant when one-half or more of its length was seen to have crossed the mandibular midline. We based the diagnosis on the clinical findings, particularly on the panoramic radiographs. After diagnosing a transmigrant canine, we documented the patient’s age and sex, the transmigrant tooth, the presence of the primary canine, symptoms, the presence of associated pathology, the radiographically identified position of the tooth and the treatment provided.
We performed a literature review by searching for the phrases "transmigrant mandibular canines," "migration impacted teeth" and "impacted mandibular canines" in the National Library of Medicine’s PubMed database. We also reviewed some articles published by the Department of Pathology of Oral and Maxillofacial Surgery, University of Barcelona Dental School, Spain, on this subject.
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RESULTS
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In eight of the 14 patients, the transmigrant tooth was the left canine, and in five patients, the transmigrant tooth was the right canine. One patient had bilateral transmigration, which resulted in there being 15 transmigrant canines (Table
). None of the canines had erupted, and a primary canine was present with 10 of the 15 impacted canines. The dental follicle was visible on the radiograph in 10 of the cases (66.7 percent), meaning that the potential for follicular cyst formation was present. In two cases, we associated the canine with a radiolucency suggestive of a follicular cyst, and, in one case, we associated the canine with pericoronal infection (Figure 1, page 1453). One of the panoramic radiographs (Figure 2, page 1453) showed transmigration of the mandibular left canine associated with a radiopacity compatible with an odontoma, and, in two cases, we identified two supernumerary teeth that may have been the cause of the canines’ change in orientation.
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TABLE Clinical and radiologic characteristics of the transmigrant impacted lower canines and associated treatment.
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Figure 2. Panoramic radiograph showing transmigration of the mandibular left canine associated with a radiopacity compatible with an odontoma.
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In the panoramic radiographs, we noted that most canines were below the mandibular incisors and contralateral canine and were parallel to the basilar of the mandible. In five patients, we found the transmigrate canines in a more distal position than the one we described previously; in three patients, the transmigrated canines were below the mandibular premolars, and, in two patients, the transmigrated canines were under the mandibular first molar. Owing to an inadequate radiographic follow-up, we could not access either the movement or the tilt of the canine in the transmigration process. Treatment consisted of surgical extraction of the transmigrant canine for eight patients, and periodic clinical and radiologic follow-up visits for six patients. We decided to manage the treatment of two of these latter patients conservatively because they refused to undergo surgical removal of the transmigrated canine. As a result, we could not confirm histologically the lesion compatible with an odontoma that we had identified in one of these patients.
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DISCUSSION
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Dental transmigration is an infrequent eruptive disorder that happens almost exclusively to mandibular canines. The rarity of transmigrant canines makes it difficult to establish their incidence, and most cases documented in the literature correspond to isolated cases.8,9 Nevertheless, some authors have attempted to define the incidence of mandibular canine transmigration. Javid5 identified a single transmigrant canine after examining the panoramic radiographs of 1,000 students. Zvolanek10 was not able to establish a statistical frequency after reviewing the dental records and radiographs of 4,000 patients, among whom no new cases were identified. In a review of 4,500 panoramic radiographs, Aydin and colleagues1 identified 14 transmigrant canines (0.31 percent) (eight mandibular canines and six maxillary canines). According to a 2002 article by Mupparapu,7 127 transmigrant canines had been reported until that time in the literature. All of the transmigrated canines described were located in the mandible.
Aydin and Yilmaz3 were the first to publish a case report of a maxillary transmigrant canine. Transmigration of an impacted maxillary canine is rare. This may be due to the negligible distance between the apexes of the maxillary canines and the floor of the nasal fossae, and to the presence of the midpalatal suture, which is a considerable barrier against maxillary canine migration.11
In our literature review, we found that transmigrant canines occur more frequently in female patients than in male patients.3,8,10 The reported patient age at presentation of the transmigrant canine varies from 8 years7 to 69 years.10 This age range coincides with that of our study (16–60 years).
While migration of a canine to the contralateral side generally is a unilateral phenomenon, mandibular canine transmigration involves a left-side tooth more often than it does a right canine.1,9,12 In the 28 cases documented by Joshi,9 53.6 percent were left-side teeth, and 32.1 percent were right-side teeth. The remaining cases involved bilateral transmigration. Migration of both mandibular canines is infrequent and occurs in only 9 to 14 percent of all transmigrant canine cases.7–9
The absence of the permanent canine within the arch beyond the normal time of eruption in a patient with no history of extraction or the abnormal retention of the primary canine suggests the presence of an impacted canine or transmigration. In these cases, it is essential for clinicians to conduct a radiologic evaluation that includes a panoramic radiograph, an occlusal radiograph, a periapical radiograph and a lateral teleradiograph of the skull.6,12
Owing to the change in orientation of the transmigrant permanent canine, exfoliation of the primary canine will fail to occur. In this context, resorption of the root of the primary canine is slow, and, as a result, the primary canine is retained in 40 to 70 percent of cases.7,9 In one-third of the cases in our study, we noted that the primary canine was retained, suggesting that the permanent canine was impacted, since agenesis of the permanent canine is infrequent.
Transmigrant canines usually are asymptomatic. Most of those we found described in the literature were diagnosed by using routine panoramic radiography. In some cases, however, pain from inflammation or infection may occur or sensory alterations may be noted in relation to the impaction of the canine.6 In other cases, the transmigrant canine may be associated with pathological conditions such as follicular cysts, odontomas or supernumerary teeth, which may be the cause of the transmigration.2,3,9,11–14 Like all impacted teeth, a transmigrant canine may develop a cystic lesion, particularly when the dental follicle is present, as we noted often in the patients in our study.
According to Mupparapu,7 45 percent of transmigrant canines found in the literature are in the mesioangular position (Figure 3), followed by 20 percent in the horizontal position (Figure 4). Few cases have been reported in which the transmigrated canine was positioned vertically in the midline.6,7 In our study, 12 of the 15 transmigrated canines (80 percent) were in the horizontal position.
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Figure 3. Transmigrant impacted mandibular canines. A. The transmigrant permanent canine is impacted in the mesioangular position. B. The transmigrant permanent canine is impacted in the horizontal position. In both cases, the primary canine is present in the dental arch.
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Figure 4. A. Panoramic radiograph showing the transmigrant mandibular right canine in the horizontal position. B. Panoramic radiograph showing the transmigrant mandibular left canine in the horizontal position.
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The causes underlying canine migration remain unclear, although a number of theories have been proposed. It generally is accepted that the impacted tooth follows the trajectory of least resistance. The tooth moves in the direction of the crown, and the mesial inclination of the follicle makes it possible for the tooth to adopt a horizontal position, migrating toward the contralateral side.12 A number of factors favoring dental transmigration have been described in the literature (Box).12–16
Although the most frequent position of the transmigrant canines is mesioangular, the inclination of the canines must exceed 30 degrees to show this tendency to cross the midline. Specifically, canines inclined between 30 and 95 degrees with respect to the sagittal plane tend to cross the midline, while transmigration takes place in the cases of angles in excess of 50 degrees.17 In this sense, the early diagnosis of mandibular canine transmigration in patients 8 to 9 years old allows for treatment in the form of surgical repositioning, autotransplantation or surgical or orthodontic management. In the cases of young patients such as these, there are increased chances for success in placing the canine within the arch, where it plays an important functional and esthetic role.6,18
The literature describes different options for managing transmigrant mandibular canines. Treatment, in part, depends on the canine’s radiographic position and clinical manifestations. Surgical extraction is indicated when malpositioning of the tooth precludes its replacement within the arch, in cases of resorption of the roots of the adjacent teeth, in the presence of infections or cyst formation, in cases in which adjacent teeth are malpositioned or in cases in which the patient has a neurological impairment.19 When patients choose extraction, clinicians need to take the innervation of the tooth into account, since the innervation originates from the original side. Consequently, anesthesia of the nerve on the original side is indicated.6,14,19
If the mandibular incisors are in the correct position and sufficient space is available to place a canine, clinicians may contemplate transplantation of the canine. Howard17 transplanted a transmigrant canine into its normal position in the arch since the required amount of space was preserved.
Another treatment option is placing the impacted canine in the dental arch through surgical or orthodontic treatment. Wertz20 was able to reposition a vestibularly impacted transmigrant canine in this way. Nevertheless, if the position of the transmigrant canine is unfavorable, repositioning in its physiological position may prove mechanically impossible.
Some clinicians prefer not to treat an impacted canine if symptoms are absent or when there is a serious risk of damaging important anatomical structures. In these cases, clinicians must perform periodic clinical and radiologic follow-up visits to ensure early detection of potential pathology associated with an impacted canine.3,6,8,9
In the cases in our study, we chose surgical extraction for eight patients, and clinical and radiologic follow-up visits for the remaining six patients. We did not consider surgical or orthodontic management or transplantation of the impacted canine to be options in any of the cases.
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CONCLUSIONS
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Migration of the mandibular canine through the mandibular midline is infrequent and normally asymptomatic. The diagnosis of transmigrant canines is based on the absence of the permanent canine in the arch and on the radiologic findings in both intraoral and panoramic radiographs. Surgical extraction is the treatment of choice in patients with transmigrant canines and associated pathology. However, in view of the risk of damaging important anatomical structures when surgery is performed, the management of asymptomatic impaction may be limited to periodic clinical and radiological follow-up visits.
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FOOTNOTES
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Dr. González-Sánchez is a resident, Master Degree Program in Oral Surgery and Implantology, University of Barcelona Dental School, Spain.
Dr. Berini-Aytés is a professor, Department of Oral and Maxillofacial Surgery, University of Barcelona Dental School, Spain, and the dean, University of Barcelona Dental School.
Dr. Gay-Escoda is the chairman and a professor, Department of Pathology of Oral and Maxillofacial Surgery, University of Barcelona Dental School, Spain, and the director, Master Degree Program in Oral Surgery and Implantology, University of Barcelona Dental School. Address reprint requests to Dr. Gay-Escoda at Centro Médico Teknon, c/Vilana 12, 08022, Barcelona, Spain, e-mail "cgay{at}ub.edu".
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REFERENCES
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- Aydin U, Yilmaz H, Yildirim D. Incidence of canine impaction and transmigration in a patient population. Dentomaxillofac Radiol 2004;33(3):164–9.[Abstract/Free Full Text]
- Gay-Escoda C, Forteza-González G, Herráez-Vilas J. Caninos incluidos: Patología, clínica y tratamiento. In: Gay-Escoda C, Berini-Aytés L, eds. Tratado de cirugía bucal. Tomo 1. Madrid, Spain: Ergon; 2004:459–96.
- Aydin U, Yilmaz H. Transmigration of impacted canines. Dentomaxillofac Radiol 2003;32(3):198–200.[Abstract/Free Full Text]
- Tarsitano J, Wooten J, Burditt J. Transmigration of nonerupted mandibular canines: report of cases. JADA 1971;82(6):1395–7.[Medline]
- Javid B. Transmigration of impacted mandibular cuspids. Int J Oral Surg 1985;14(6):547–9.[Medline]
- Auluck A, Nagpal A, Setty S, Pai K, Sunny J. Transmigration of impacted mandibular canines: report of four cases. J Can Dent Assoc 2006;72(3):249–52.[Medline]
- Mupparapu M. Patterns of intra-osseous transmigration and ectopic eruption of mandibular canines: review of literature and report of nine additional cases. Dentomaxillofac Radiol 2002;31(6):355–60.[Abstract]
- Camilleri S, Scerri E. Transmigration of mandibular canines: a review of the literature and a report of five cases. Angle Orthod 2003;73(6):753–62.[Medline]
- Joshi MR. Transmigrant mandibular canines: a record of 28 cases and a retrospective review of the literature. Angle Orthod 2001;71(1):12–22.[Medline]
- Zvolanek J. Transmigration of an impacted mandibular canine. Ill Dent J 1986;55(2):86–7.[Medline]
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- Al-Waheidi E. Transmigration of unerupted mandibular canines: a literature review and a report of five cases. Quintessence Int 1996;27(1):27–31.[Medline]
- Shapira Y, Kuftinec M. Intrabony migration of impacted teeth. Angle Orthod 2003;73(6):738–43.[Medline]
- Mitchell L. Displacement of a mandibular canine following fracture of the mandible. Br Dent J 1993;174(11):417–8.[Medline]
- Peck S. On the phenomenon of intraosseous migration of nonerupting teeth. Am J Orthod Dentofacial Orthop 1998;113(5):515–7.[Medline]
- Howard R. The anomalous mandibular canine. Br J Orthod 1976;3(2):117–21.[Medline]
- Torres-Lagares D, Flores-Ruiz R, Infante-Cossío P, García-Calderón M, Gutiérrez-Pérez J. Transmigration of impacted lower canine: case report and review of the literature [in English, Spanish]. Med Oral Patol Oral Cir Bucal 2006;11(2):E171–4.[Medline]
- Alaejos-Algarra C, Alaejos-Algarra E, Berini-Aytés L, Gay-Escoda C. Transmigración del canino mandibular: presentación de un caso clínico y revisión de la literatura. Rev Act Odontoestomat Esp 1996;56:67–71.
- Wertz R. Treatment of transmigrated mandibular canines. Am J Orthod Dentofacial Orthop 1994;106(4):419–27.[Medline]
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ABSTRACT
SUBJECTS AND METHODS
