Mechanotherapy

There are multiple ways to proceed with the traction of an impacted canine after its ligation and all impacted teeth cannot be pulled in the same way. Often, one, two, even three traction techniques are combined. Therefore, here I present three of my favorite methods among several others that I was able to use in my career to bring an impacted canine in occlusion.

Traction with fixed appliances and auxiliary wire

The series of occlusal view pictures of the maxillary arch shows the evolution of the traction of 2 impacted canines.

On picture A, taken 7 days after the exposure and surgical ligation, you observe that an auxiliary wire is inserted in the auxiliary tube located on the SPEED™ brackets. This auxiliary wire (blue arrow) is engaged into loops of the ligature wire which comes out of transmucosal openings.

The bend in the auxiliary wire indicates the amount of activation required to initiate the eruption movement of the impacted tooth. The wire used is a nickel-titanium shape-memory alloy. When it is activated in that manner, the nickel-titanium wire tries to go back to its original shape, which corresponds to the main arch. Since this auxiliary wire is attached to the ligature of the canine, it thus drags the canine with it while going back to its original shape. The wire is reactivated every 6 to 8 weeks by shortening the twisted wire of the canine ligature.

On picture B, 14.4 weeks after the traction was initiated, we observe that the left canine is visible. During the surgery, the cleat had been bonded to the lingual surface, because this is often the surface that is accessible surgically. Traction from the lingual surface makes the tooth rotate. A cleat was bonded to the buccal surface and a ligature wire is attached to it and connects the tooth to the auxiliary wire. Traction from the buccal cleat will make the tooth rotate on the opposite side and will allow the bonding of a bracket on the buccal surface.

The right canine was more deeply and mesially impacted. The white arrows indicate that the tip of the canine goes beyond half of the root of the right central incisor while the left canine is barely aligned with the root of the left central incisor. The right canine will require 13 more weeks before it is visible in the mouth.

It was possible to bond brackets on the buccal surface of the upper canines (13 and 23) thirty-four (34) weeks after the traction of the canines was initiated. Picture C shows the evolution at 41 weeks. The left canine is engaged in the main arch while the right canine is engaged in an auxiliary arch. The treatment continued and other problems not related to impacted canines were corrected. Picture D shows the final result.

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Traction with removable appliance followed by fixed appliances

A removable appliance has more benefits during the traction of an impacted canine. It offers an excellent anchorage and an excellent resistance to reciprocal effects of forces necessary to move the canines.

Picture B: The palatal arch of the removable appliance is rigid. Double helix springs make it possible to apply a relatively constant force for the deflection necessary to the engagement in the twisted ligature wire. The cantilever armspring is pre-activated based on the direction indicated by the dotted blue line. The cantilever is activated by engaging it into the loop of the twisted wire. The impacted tooth is thus subjected to the force of the cantilever which tends to return to its original position.

Picture C: The loop of the twisted wire is shortened, which reactivates the force of the spring.

Picture D: Eleven weeks after the installation of the removable appliance, brackets are bonded to the canines and an alignment wire is inserted.

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Traction of an impacted canine in vestibular position with removable appliance followed by fixed appliances

The following example shows the treatment of a patient having three (3) impacted canines.

•1: upper right canine over the lateral incisor (transposition).

•2: upper left canine in horizontal position right under the left nostril.

•3: lower right canine over the root of the left lateral incisor.

The canines were ligated following a surgical closed flap exposure. We saw that Dr Vanarsdall recommends an open exposure instead, but let’s say that this closed eruption approach is frequently used in Quebec City.

On picture A, we can see by transparency in the red circle of the image on the left the ligature cleat bonded to the canine. Elastics are positioned on the removable appliances and in the loops of the twisted wire to bring the force vector backward to straighten up and push back the impacted teeth.

On picture B, the cleat of the canine is exposed through the gingiva. The loops are engaged into the cantilevers for a more vertical traction. The right canine erupted in the mouth 2 months into the treatment. The mandibular traction is made possible by the elastic.

On picture C (D), the cantilever is bonded directly to the cleat of the right canine. On the left, traction continues with an elastic and the cantilever.

On picture D (E), the left canine erupted through the gingiva. We notice a band of keratinized gingiva at the back of the cleat. On the left, a large pad of keratinized gingiva is visible at the neck of the canine.

The evolution of the eruption of the canines during the subsequent major treatment shows a wide band of keratinized gingiva at the neck of the permanent canines (green arrows). The lower canine which we can see the cleat by transparency through the gingiva presents an adequate gingival festoon once the eruption is completed.

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Traction with fixed appliances and cantilever arch

Here is the evolution of the traction treatment of the 2 palatal canines for which the surgical approach was described on the page on the surgical exposure technique of palatally impacted canine.

At 2 weeks post surgery (picture A), the twisted ligatures are activated by NiTi cantilever springs (shape-memory alloy: Sentalloy Uprighting Springs GAC # 02-000-00 and 02-000-01). Another example of use of cantilever is shown on the page on treated case/Classe II division 2.

At 12 weeks (picture B), the left canine is already visible in the mouth. The right canine (black arrow) is submerged by the keratinized palatal tissue. The forward traction of the cantilever drags the crown of the impacted tooth toward the root of the lateral incisor on one side and the thickness of the very firm keratinized tissue can slow down the movement. A wider opening in the flap would have been preferable and would have allowed a less blindly traction.

At 24 weeks (picture C), an elastic chain is engaged in the loop of the ligature to pull the tooth laterally and backward. The cleat bonded to the buccal surface of the left canine is now exposed in the mouth and an elastic chain is attached to it. This chain allows a posterior traction on an anchor point located on the buccal surface of the canine. Yet, the buccal surface is turned too much forward. The force will rotate the tooth outward and will move it away from the lateral incisor.

At 31 weeks (picture D), a bracket is bonded to the buccal surface of the left canine and an auxiliary wire is engaged. On the right, the loop of the twisted wire is engaged in the main arch. The impacted tooth is now palpable under the labial mucosa.

At 38 weeks (picture E), the left canine is well aligned and the bracket is engaged in the main archwire. A new ligature connects the canine to the main archwire to pull the tooth closer to the buccal side and make the tooth accessible to bond a bracket.

At 41 weeks (picture F), it is finally possible to bond a bracket and engage an auxiliary wire.

At 47 weeks post surgery, the bracket of the right canine is repositioned. We notice the same type of rotation toward the mesial (front) surface of the crown. We will need to rebond the bracket at least once more to obtain an optimal position of the bracket on the tooth. The left canine presents an adequate position in the arch.

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