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Ectopic Eruption of Permanent Canines

 

 

» By: Dr. Lama Hussam Jarrah

BDS.,MSC. JBO

 

The transition from the primary dentition to the permanent dentition is not always a smooth sailing process. Disturbances in the eruption of permanent canines are common. Maxillary canines are prone to ectopic eruption since they have the longest and most tortuous eruption route.

Ectopic eruption may lead to various complications like impaction, loss of bone induction, dentigerous cyst formation and resorption of adjacent teeth (1).Careful supervision of the developing dentition and early diagnosis of ectopic eruption may prevent such complications. Therefore, it is important to evaluate the canine position no later than 10 years of age (2).

Diagnosis of Ectopically Erupting Canines:

Diagnosis requires a thorough clinical and radiographic examination.

Clinical Examination:

Clinical examination include visual inspection and palpation of the buccal sulcus and palatal mucosa. The clinician should suspect Ectopic eruption if the following clinical signs are present;
1- Prolonged retention of the deciduous canine.
2- Absence of a normal labial canine bulge.
3- Difference in palpation between right and left canine bulges.
4- Presence of a palatal bulge instead of a buccal one.
5- Distal tipping or migration (splaying) of the lateral incisor (figure 1).

 

 

» (Fig. 1)

Distal tipping of the lateral incisor.

 

 

 

Radiographic Examination:

Variety of radiographs could be taken to help detect ectopic eruption and localize the position of the permanent canines. Periapical radiographs localize the position of the canines in the mesio-distal and superoinferior direction. The buccolingual position could be determined using tube shift technique (two periapical radiographs taken from two different angulations), Occlusal vertex and modified occiptomental views.

Panoramic radiographs give valuable information that should not be underestimated. Since they are taken routinely for orthodontic records, they are an excellent screening tool for detecting ectopically erupting canines. Sector location and angulation of the unerupted canine can be analyzed from the panoramic X-ray.

1.Angular Measurement:
A horizontal reference line is chosen, Warford et al (3) used a bicondylar line passing through the most superior point of the condyles (figure 2). The mesial angle formed by using the constructed horizontal line and the long axis of the unerupted canine is measured. The higher the angle the less tendency to ectopic eruption and therefore the less tendency to impaction. Warford et al, showed in their study angulation was higher for non-impacted teeth, with a mean of 75.12° compared with 63.20° for impacted teeth.

2. Sector Measurement:
Three lines are drawn; one that coincide with the mesial surface of the lateral incisor, the other line with the distal surface of the lateral incisors, and the last one bisect the lateral incisor into two halves. (4) These lines divide the area into four sectors; sector I, II, III, IV as shown in (figure 3). If canines are in sector I, they are not ectopically erupting. Therefore, there is no risk of impaction. The risk of impaction becomes higher in sector II, III, and IV.

 

(Fig. 2): Angular measurement.

(Fig. 3): Sector locations.

 

When angular measurement is compared to sector measurement, sector measurement is superior in predicting ectopic eruption. Warford et al (3) found that sector location of the cusp tip of the unerupted canine is the most important predictor of eventual impaction. Eighty two percent of impacted canines were found in sectors II, III, and IV. However, in border line cases where the canine is in sector II, angulation adds to the prediction of eventual impaction.

For Further radiographic investigations, Computed tomography and CT scan accurately localize the position of the canine and it's relation to neighboring structures. It reveals the presence of even a small root resorption, and locates it in all three planes. This gives the clinician a more complete picture of the situation. However, weight of information gained from them should always be evaluated against their high cost. In those cases where the canine images overlap the lateral incisor root excessively, their value increases.


Management of Ectopically Erupting Canines:
Once ectopic eruption of permanent canines is detected, deciduous canines expire and should be extracted. Their extraction should be done in a planned fashion.  Clinical studies (6, 7) showed that extraction of the maxillary deciduous canines before the age of 11, have favorably influenced the eruption path of the permanent canines. Ectopically erupting permanent canines will normalize it's path.  If the permanent canine crown is distal to the midline of the lateral incisor, the eruption path will normalize in 91% of the cases. However, If the canine crown is mesial to the midline of the lateral incisor this will drop to 64%. (6)

After extraction of the deciduous canines, the space should be maintained, by a proper space maintainer. Four to six months are given for the permanent canine to normalize it's eruption path. A new panoramic X-ray is then taken to re-evaluate the position.

Complications of Ectopically Erupting Canines:   
Lack of early detection and application of this preventive protocol could lead to impaction (figure 4, 5). The panoramic X-ray in figure 4, shows the permanent canines ectopically erupting and are located in sector III, the lateral incisors are congenitally missing. No interceptive treatment was applied. After two years a new panorama was taken. The panorama showed that the canines moved mesially, and are overlapping the central incisors (figure 5). Modified occipto-mental view revealed the palatal impaction of these canines (figure 6). Surgical exposure and orthodontic recovery of the canine was the solution (figure 7, 8).

 

(Fig. 4): Ectopic eruption. (Fig. 5): Canines moved mesially after 2 years.

(Fig. 6): Palatal impaction of the canines. (Fig. 7): After surgical exposure of the palataly
impacted canines.

 

 

 

» (Fig. 8)

The maxillary canine after orthodontic recovery.

 

 

 

Root resorption is another important complication of ectopic eruption. Root resorption of lateral incisors neighboring ectopically erupting maxillary canines can be expected in about 12% , indicating a prevalence of about 0.7% in the 10–13 year age group (5). Incisor resorption can be swift, silent, and devastating. Children seldom complain of pain or discomfort.  Most resorption is found in midroot, on the labial or lingual surfaces where it can not be detected on periapical radiographs (Figure 9, 10).

 

(Fig. 9): Ectopic eruption of the upper right canine. (Fig. 10): Resorption of lateral incisor.

 

 

Summary
Disturbances in the eruption of permanent maxillary canines are common. Careful supervision of the developing dentition and early diagnosis of ectopic eruption may prevent impaction of these teeth and resorption of the neighboring incisors. Protocol for management of ectopically erupting maxillary canines is; clinical and radiographic evaluation combined with primary canine removal followed by maintaining the space. This protocol is effective when the condition is detected early. Therefore, it is important to evaluate the canine position no later than 10 years of age.


Reference:
1. Juri Kurol: Early treatment of tooth-eruption disturbances. Am J Orthod Dentofacial Orthop. Volume 121, pages 588-591, June 2002.
2. Sune Ericson, Juri Kurol: Incisor Resorption caused by Maxillary Cuspids A Radiographic Study.  Angle Orthodontist, 1987 No. 4, 332 – 346.
3. John H Warford, Ram K Grandhi and Daniel E Tira: Prediction of maxillary canine impaction using sectors and angular measurement.  Am J Orthod Dentofacial Orthop. Volume 124, pages 651-655, Dec 2003.
4. Lindauer SJ, Rubenstein LK, Hang WM, Anderson WC, Isaacson RJ: Canine impaction identified early with panoramic radiographs. J Am Dent Assoc. 1992;123:91-97.
5. Ericson S, and Kurol J: Radiographic examination of ectopically eruption maxillary canines. Am. J. Orthod. 91:483–492.
6. Erikson S, Kurol J: Early treatment of palatally erupting maxillary canines by extraction of the primary canines. Eur J Orthod. 1988; 10: 283–295.
7. Power S, Short M:  An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption. Br J Orthod. 1993; 20:215–223.