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September's Tip: Treatment of Impacted Lower Permanent Cuspid: Clinical and Mechanical Considerations

 By: Dr. Pierre Pellan

By: Dr. Pierre Pellan

Mandibular canine impaction is way less frequent than is maxillary canine impaction.  (1, 2, 3). The best way to treat impaction of lower permanent cuspids is simply to prevent its occurrence. Each year, our office welcomes 15-year-old patients who are referred because their family dentist wondered why the permanent cuspids had not erupted still.

The best approach remains early detection and preventive measures that allow for spontaneous correction before actual impaction occurs. For cases where early detection did not happen or prevention failed, or for cases that slipped the dentist's attention, orthodontic treatment with deimpaction of the cuspids is one of the favorite option. Here is an example that describes a safe technique to decrease mechanical side effects when doing so.

A 15-year-old girl with excellent health and normal skeletal features presented for a second opinion in September 2009. A recent panogram showed delayed eruption of her upper cuspids and impaction of her lower right cuspid (Figure 1). Her family dentist had planned on placing a gold chain on teeth 13, 23 and 43 and start orthodontic traction on all three teeth. I recommended we extracted all three primary cuspids and monitor the natural eruption of teeth 13 and 23, since I was confident they would erupt by themselves. Tooth 43 was to be managed with orthodontic deimpaction procedures. Still a preventive panogram should have been taken around age 8 where appropriate extractions of the primary cuspids could have been performed in order to prevent such situations from occurring.

The inclination of an unerupted lower cuspid's crown from the median sagittal plane should be measured on the panogram:

September Tip 1.jpg
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if it is more than 30 degrees, orthodontic measures could be necessary in order to upright that tooth. Should it be more than 45 degrees, periodontal issues with bony dehiscence are more likely to happen with orthodontic treatment only. If the mandibular cuspid bud has a 50 to 90 degree inclination from the midsagittal plane in young children, it will drift toward the symphysis. The latter will usually cause labial tilting of the lower incisors and even force their root into the mandible's lingual cortical plate. (4)

Going back to the clinical case and after the extractions were performed, I waited a month and bonded brackets on all available teeth except second molars since they had not erupted enough (Figures 2 to 6). When dealing with high cuspids on the upper arch and low cuspids on the lower arch, it is very helpful to use

September Tip 3.jpg
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brackets with decreased values of torque on the incisors (more negative torque) that will counteract the secondary effects of moving teeth forward as we will guide these teeth toward their adequate vertical position. In this case I used +2 degrees for upper centrals, -5 for upper laterals and -11 for mandibular incisors.

September Tip 6.jpg

Also in the presence of impacted cuspids, 3D images will provide great amount of information and in this case, it confirmed the position of the lower cuspid crown. It was lying in front of the incisors apices, reassuring that a vertical upper traction would prove to be successful (Figures 7 and 8). It is well known that 3D images can alter the diagnosis and treatment plan of impacted teeth. (5)

Treatment of impacted lower cuspids can be a long and arduous work. Clinicians need to be careful when talking about treatment duration, since the portion allowed for actual deimpaction is difficult to precisely estimate.

Since it is very common that attached gingiva is very thin in the anterior region of the lower anteriors, treatment protocol should include mechanically bringing the cuspid tip to its proper location before it erupts too far forward, which could lead to a periodontal defect. Also the clinician performing the surgery for the bonding of the attachment on the crown will also ensure that she or he leaves appropriate amount of keratinized tissue in front of the impacted tooth.

I found the best way to proceed was to start with a regular wire sequence in both arches. In my practice, that would be for the lower arch:
0.014 CuNiTi
0.018 CuNiTi
0.014 x 0.025 CuNiTi
0.018 x 0.025 CuNTi
0.019 x 0.025 SS or TMA

When engaging the 0.018 x 0.025 CuNiTi, the patient is sent for surgery, with specific instructions to bond the attachment on the buccal side of the crown, as close to the incisal tip as possible. On the next appointment, the final base arch is engaged (0.019 x 0.025 SS or TMA), and a secondary wire of very small force and diameter (0.013 CuNiTi) is inserted into the auxiliary horizontal slot (Figure 9) of the next two brackets mesial and distal of the lower cuspid position (Figure 10a and 106). This small wire is linked and slightly activated in direction of the gold chain bonded to the impacted tooth (note on Figure 10c that the panogram taken after the visit to surgery showed a small piece of chain that was not attached to the main one, but these rings disappeared after some time). From there, only low forces and patience are permitted in order to decrease the risks of necrosis and the biomechanical side effects (Figure 11). Since the lower cuspid has a massive root, it offers significant reciprocal effects on any system that tries to displace it.

Also it is recommended that bracket on the lateral incisor be removed so it can act as a free body, since it is very likely that its root is in contact with the cuspid. This could prevent unwanted resorption of the incisor root.

Once the crown is near its good position, the wire sequence is started over with the very first wire but this time, the lower cuspid is included in the set-up (Figures 12a and 126). The bracket on the lateral incisor is put back and also included with the others.

Overall treatment time was 31 months and end results were very satisfying. After periodontal evaluation, I recommended that the patient received a gingival graft on tooth 43 to increase the keratinized tissue for that tooth (Figures 13 to 20).

Be it for upper or lower impacted teeth, I found this technique to consistently offer great results, but patients have to be instructed at the onset of treatment that more time is necessary for this delicate operation when compared to standard treatment duration.

References

1.      D'Amico RM, Bjerklin K, Kurol J, Falahat B. Long-term Results of Orthodontic Treatment of Impacted Maxillary Canines. Angle Orthod 2003: 73:231-238.

2.      Aydin U, Yilmaz HH, Yildirim D. Incidence of canine impaction and transmigration in a patient population. Dentomaxillofac Radiol2004: 33:164-9.

3.      Alaejos-Algarra C, Berini-Aytes L, Gay-Escoda C. Transmigration of mandibular canines: Report of six cases and review of the literature. Quintessence Int. 1998: 29:395-398.

4.      Korbendau J-M, Patti A. Clinical success in surgical and orthodontic treatment of impacted teeth, Quintessence, 2006, pp.125-128.

5.      Botticelli S, Verna C, et al: Two- versus Three-dimensional Imaging in Subjects With Unerupted Maxillary Canines. Eur J Orthod; 2011; 33 (August): 344-349.

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