Incidence of canine impaction and transmigration in a patient population

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1 (2004) 33, q 2004 The British Institute of Radiology RESEARCH Incidence of canine impaction and transmigration in a patient population U Aydin*, HH Yilmaz and D Yildirim Department of Oral Diagnosis and Radiology, School of Dentistry, Süleyman Demirel University, Isparta, Turkey Introduction In this study, 4500 consecutive panoramic radiographs were prospectively reviewed. The incidence of canine impaction was found to be 3.58% and the incidence of canine transmigration was 0.31%. There were six maxillary and eight mandibular transmigrant canines. The incidence of impacted canine teeth and transmigration of maxillary and mandibular canines may be more frequent than was previously thought, at least in some populations. (2004) 33, doi: /dmfr/ Keywords: tooth, migration; cuspid; tooth, impacted; radiography, panoramic Maxillary canine impaction is a well known dental anomaly and the incidence is in the range %. 1 3 Mandibular canine impaction is less frequent and the incidence was reported to be 20 times lower than that for maxillary canines. 4 Migration of a tooth across the midline is an even rarer anomaly; however, at least 157 cases of mandibular canine transmigration have been published Although the vast majority of the cases were impacted, erupted cases were also presented. 5,11 13 Most of the cases were unilateral, but transmigration may also be bilateral. 6,11,14 17 Previously this condition had been described only in mandibular canine teeth. 5,11 In a recent publication, however, one case of an impacted maxillary canine was reported. 6 There are few reports on the incidence of transmigration. 14,18 In addition, owing to the lack of published reports on maxillary cases, little is known about their transmigration patterns. In this study, we attempted to determine the incidence of transmigrant maxillary and mandibular canine teeth in a Turkish subpopulation. Another purpose of the study was to evaluate transmigrant maxillary and mandibular canine teeth with regard to their transmigration patterns. The incidence of impacted maxillary and mandibular canines was also determined. Materials and methods In this study, 4500 consecutive panoramic radiographs made in our Department of Oral Diagnosis and Radiology *Correspondance to: Ulkem Aydin, Süleyman Demirel Universitesi, Dishekimligi Fakultesi, Oral Diagnoz ve Radyoloji Bolumu, Dogu Kampusu, Çunur, Isparta, Turkey; ulkem_aydin@yahoo.com Received 12 January 2004; accepted 2 March 2004 were prospectively reviewed. Intraoral examination was also performed for all patients. A tooth was accepted as impacted if the tooth was not exposed to the oral cavity and the age of the patient was above 16 years. The incidence of canine impaction and transmigration was determined, and the features of the transmigration cases were evaluated, including demographic information. Tracings of the radiographs showing transmigrated canine teeth were made on acetate paper using a 0.5 mm lead pencil, in a room with subdued lighting on a standard viewbox, which was masked to cover all but the radiograph. The impacted teeth and all the anterior teeth (if present) were traced. The inferior orbital margin was used as a horizontal reference plane. A vertical line was drawn from the midpoint of this horizontal line, to demonstrate the midline. Transmigration was defined as migration of a tooth across the midline regardless of the distance. The case was excluded if transmigration could not be confirmed by occlusal radiography. The mesial angle formed between the long axis of the transmigrant canine teeth and the mid sagittal plane was also recorded. Figures 1a and 1b show a tracing superimposed on the panoramic radiograph, and the occlusal radiograph, respectively. The transmigrant mandibular canines were classified according to Mupparapu. 5 The classification can be summarized as: Type 1, canine positioned mesio-angularly across the midline, labial or lingual to the anterior teeth; Type 2, canine horizontally impacted near the inferior border of the mandible inferior to the apices of the incisor teeth; Type 3, canine erupting on the contralateral side; Type 4, canine horizontally impacted near the inferior border of the mandible below the apices of posterior teeth

2 Impaction and transmigration UAydinet al 165 Figure 1 Patient 1 (maxillary). (a) Panoramic radiograph and superimposed tracing demonstrating canine transmigration. (b) Occlusal radiograph showing right canine transmigration on the contralateral side; Type 5, canine positioned vertically in the midline with the long axis of the tooth crossing the midline. Results In the present study, the incidence of canine impaction was found to be 3.58%. Thirty-three (20.49%) patients had more than one impacted maxillary or mandibular canine. The number, incidence, age and gender ratio for impacted canines are shown in Table 1. Among the 4500 patients who had panoramic radiographs, 14 had transmigrant canines. The incidence of canine transmigration was 0.31%. The number, incidence, age and gender ratio for transmigrated canine teeth are given in Table 2. Among the six transmigrant maxillary canine teeth, three canines migrated from the left side and three from the right, and only their crowns were crossing the midline up to half of their length. Figure 2 shows a case of a transmigrated maxillary canine. Three patients had retained deciduous canines at the time of diagnosis. Three patients had dental developmental anomalies, but none of the patients had associated pathologies. Figure 3 shows a transmigrated maxillary canine and microdont lateral incisors. The clinical and radiographic features of the cases are shown in Table 3. Five of the patients were not aware of the condition and there were no complaints related to the transmigrant canine teeth. The patients attended because of orthodontic or prosthetic purposes or other dental problems. One patient was complaining of trauma to the soft tissues, as the tooth was partially erupted (Figures 4a and 4b). In four of the patients, the decision was to keep the patient under observation with periodic panoramic examinations as they denied surgical treatment. Two patients were operated for extraction and there were no intraoperative or postoperative complications. There were eight transmigrant mandibular canines. Five canines migrated from the left side and three from the right. Two patients had retained deciduous canines and six had exfoliated deciduous canines. All of the patients had dental developmental anomalies and/or associated pathologies. Classification of transmigrant mandibular canines, and clinical and radiographic presentations of the cases are shown in Table 4. Figure 5 demonstrates a case classified as Type 1. There were no related complaints and seven of the patients were not aware of the condition. One patient was aware of her impacted tooth because of a previous radiographic examination made in another centre, and she attended for a follow-up radiographic evaluation (Figure 6). In five of the patients, the decision was observation with regular panoramic examinations as they denied surgery. Three of the patients were operated through intraoral approaches and there were no intraoperative or postoperative complications. Axial inclinations of the transmigrant maxillary canine teeth varied from 438 to 828 (mean 62.58) and the mandibular cases varied from 408 to 938 (mean ). The mean axial inclination for all transmigration cases was Discussion The incidence of maxillary canine impaction varies between 0.8% and 2.8%, depending on the population studied. 1 3 Mandibular canine impaction is regarded as a much rarer phenomenon and there are limited number of Table 1 Incidence, age and gender ratio for canine impaction Cases Incidence (%) No. of teeth Males Females Gender ratio Mean age (years) Age range (years) Canine impaction M1:F Maxillary canine impaction M1:F Mandibular canine impaction M1:F Table 2 Incidence, age and gender ratio for transmigrant canines Cases Incidence (%) Males Females Gender ratio Mean age (years) Age range (years) Canine transmigration M1:F Maxillary canine transmigration M1:F Mandibular canine transmigration M1:F

3 166 Impaction and transmigration UAydinet al Figure 2 Patient 5 (maxillary). Cropped panoramic radiograph revealing transmigrated left maxillary canine, absence of left incisor, retained left deciduous canine and microdont right lateral Figure 3 Patient 4 (maxillary). Occlusal radiograph showing transmigrated right maxillary canine studies revealing its frequency of occurence. In one study, eight unerupted mandibular canines were found in 7886 individuals, and in another study 11 impacted mandibular canines were found in 5000 individuals, resulting in an incidence of 0.10%. 1,19 In our patient population, the incidence of maxillary canine impaction was 3.29% and the incidence of impacted mandibular canines was 0.44%. In another study made on 1000 Turkish patients, the incidence of maxillary canine impaction was 2.9% and mandibular canine impaction was 0.3%. 20 The results of our study are in line with this report. In one study, 4898 Saudi patients aged 13 years and older were examined and the results indicated that 3.6% had at least one impacted cuspid. 21 Another study analysed year-old children presented for orthodontic treatment and the results revealed 101 cases of impacted cuspids (5.43%). 22 These results indicate that the incidence of canine impaction may be higher in some populations. Transmigration of canine teeth is regarded as a rare entity, but there are a limited number of studies on its incidence. Javid 14 reported a radiographic survey of 1000 students that revealed one transmigrant impacted mandibular canine, and Zvolanek 18 reviewed 4000 patient records but failed to find any cases. In our prospective study of 4500 patients panoramic radiographs, 14 cases of canine transmigration were found, revealing an incidence of 0.31%. Further studies are necessary to reveal the incidence of transmigration in other populations. In the present study, males tend to have this condition more frequently than females, possibly owing to the limited number of cases. When the results of the present study were added to the available data, the gender ratio for mandibular canine transmigration was found to be 1M: 1.30F in a total of 150 cases in which the gender of the patient was mentioned. Despite the differences reported in case series and reviews, an overall evaluation shows that canine transmigration is encountered more frequently in females than in 5,6,8 11 males. Transmigration was defined as movement of an unerupted mandibular canine across the midline without the influence of any pathological entity. 14 However, it was also noted that it may not be possible to decide whether pathological conditions were responsible for the transmigration of the teeth or not. 5,11 Therefore, teeth that were associated with dentigerous cysts and odontomas and crossing the midline were considered as transmigrant. Another definition for transmigration 6,9,11,14,23 26 was an impacted tooth that has crossed the midline more than half of its length. 14 On the other hand, it was also stated that the more important consideration should be the tendency of the tooth to cross the midline, not the distance of the migration, and the stage of transmigration will depend on the time of diagnosis. 11 Transmigration was also defined as pre-eruptive migration of a tooth across the midline. 27 Peck 28 states that intraosseous migration of unerupted, horizontally impacted mandibular canine has been called transmigration because of the mesial movement of the tooth across the mandibular symphysis to the opposite of the lower jaw. These descriptions present the need for a consensus definiton for transmigration and Table 3 Features of transmigrant maxillary canine cases Case No. Axial inclination Right/left Retained deciduous Dental anomalies Associated pathologies Age (years) Sex Right 2 (edentulous) 47 F Right 2 Impacted maxillary left canine (partially 52 F edentulous) Left þ 16 F Right þ Microdont maxillary lateral incisors 22 M Microdont right maxillary third molar Left þ Absence of left maxillary lateral incisor 21 M Microdont right lateral incisor Left 2 (edentulous) 74 M

4 Impaction and transmigration UAydinet al 167 Figure 4 Patient 3 (maxillary). (a) Intraoral photograph showing partially erupted maxillary canine tooth. (b) Occlusal radiograph revealing transmigrated canine tooth Table 4 Classification of transmigrant mandibular canines and features of the cases Case No. Type Axial inclination Right/left Retained deciduous canine Dental anomalies Associated pathologies Age (years) Sex Right 2 Pericoronal radiolucency 11 M Left 2 Pericoronal radiopacity 47 M (odontoma?) Right 2 (partially edentulous) 54 M Left 2 Partially impacted third molars Enlargement of the follicle 18 M Right þ Partially impacted mandibular third molars 22 F Retained maxillary right deciduous canine Absence of right maxillary lateral incisor Left þ Impacted right maxilary canine and retained 28 F right deciduous maxillary canine Impacted right mandibular canine and retained right deciduous mandibular canine Partially impacted right mandibular third molar Left 2 Partially impacted mandibular third molars 24 M Left (edentulous) Crown resorption 70 M Pericoronal radiolucency Figure 5 Patient 2 (mandibular). Cropped panoramic radiograph showing left canine positioned mesio-angularly across the midline (Type 1) elimination of terms limiting the definition with mandibular canine transmigration. Although a number of factors have been suggested, the aetiology and exact mechanism of transmigration is still unclear. 10 Rotation of tooth buds was proposed as an Figure 6 Patient 5 (mandibular). Cropped panoramic radiograph showing transmigrated canine tooth horizontally impacted near the inferior border of the mandible (Type 2) aetiologic factor for impaction. Therefore, in the presence of a strong eruptive force, mesioangular or horizontal rotation of the tooth bud may result in transmigration unless the tooth faces a resistance from tooth roots, neighbouring anatomic structures or dense bone. To date, only one case of maxillary canine transmigration had been reported and we encountered six cases of maxillary canine transmigration in

5 168 Impaction and transmigration UAydinet al a total of 4500 patients. 6 The rarity of maxillary canine transmigration may be attributed to the shorter distance between the roots of maxillary incisors and the floor of the nasal fossa as well as the larger roots of maxillary incisors, which may be a barrier for transmigration. In addition, the larger cross-sectional area of the mandibular anterior region in comparison with the anterior maxilla may be a reason for the higher frequency of mandibular canine transmigration. Mandibular canine transmigration was suggested to have genetic determinants, as there were other associated dental developmental anomalies suggesting genetic origins, such as hypodontia, palatally displaced canines and bilateral occurrence of this anomaly. 28 Palatally displaced canines, hypodontia and diminutive lateral incisors were suggested to have a genetic aetiology and are interrelated In the present study, four out of six patients with transmigrant maxillary canines had such dental developmental anomalies and two of the patients were edentulous. Two of the patients with transmigrant mandibular canines had dental anomalies and two of them were partially or totally edentulous. However, no common aetiology was found in our study and the genetic aetiology of transmigration needs further investigation. In the present study, the transmigrated maxillary canines did not show variations in their location; their crowns were crossing the midline up to half of their length, but their axial inclinations varied between 438 and 828. Although seven of the mandibular cases were classified as Type 1 (mesio-angularly impacted), their axial inclinations ranged between 408 and 768. Impacted canines that are between 308 and 958 of angulation have the tendency of crossing the midline. 11,32 In our study, axial inclinations of all the cases were greater than 308 (40 938), in accordance with previous findings. However, with regard to such great variations, it may be useful to refer to the axial inclinations of the cases for ease of classification. Seven of the mandibular cases in the present study fitted into Type 1. This result supports the finding that most of the transmigrant canines are positioned mesio-angularly across the midline, labial or lingual to the anterior teeth. 5 However, determining the transmigration patterns with regard to their relationship with other teeth is not possible when the patient is totally or even partially edentulous. In addition, dental midlines may not always be coincident with each other and with the mid sagittal plane. Therefore, although the relationship of the transmigrated teeth with other teeth is important, classifications should also be based on the relationship of the transmigrant teeth with the midline or with anatomic structures other than teeth, provided that there are no patient positioning errors during the radiographic examinations. In conclusion, the incidence of impacted canine teeth and transmigration of maxillary and mandibular canines may be more frequent than was previously thought, at least in some populations. Future studies may reveal other cases in varying stages of intraosseous migration and positioning in the maxilla and establishment of a classification system will be possible. References 1. Grover PS, Lorton L. The incidence of unerupted permanent teeth and related clinical cases. Oral Surg Oral Med Oral Pathol 1985; 59: Kramer RM, Williams AC. The incidence of impacted teeth. A survey at Harlem hospital. Oral Surg Oral Med Oral Pathol 1970; 29: Dachi SF, Howell FV. A survey of 3,874 routine full-mouth radiographs: II. A study of impacted teeth. Oral Surg Oral Med Oral Pathol 1961; 14: Rohrer A. Displaced and impacted canines. Orthod Oral Surg Int J 1929; 15: 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: Aydın Ü, Yılmaz HH. Transmigration of impacted canines. Dentomaxillofac Radiol 2003; 32: Dhawan P, Roychoudhury A, Prakash H, Duggal R. 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