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Treatment Planning a Case of Bilateral Canine Impaction

Published: March 2014

Bulletin #31- March 2014

Treatment Planning a Case of Bilateral Canine Impaction

 Under construction

This month, I received a request for advice on the Clinical Consultation page of this website from a colleague and former student of mine, for one of his patients. The problem concerned was interesting from several points of view and I considered it well worth sharing with my readers for the lessons that it has for all of us, but particularly those who have not yet recognized the information that becomes available with the use of cone beam CT for cases with impacted teeth.

I received facial photographs of the patient in profile and en face which in the present context do not contribute to the discussion and will not be presented here. In contrast, the intra-oral views of the dentition were relevant and enlightening.

CCC.Fig.1a

Fig. 1. Intra-oral clinical photographs of the pre-treatment dentition .

The teeth were in the mixed dentition stage (Fig. 1), with deciduous maxillary canine and second molar retained on each side and a deciduous first molar on the left side of the maxilla. The maxillary second permanent molars were not erupted. The mandible displayed a full and ideally aligned permanent dentition including erupted second molars. The occlusion of the posterior teeth was normal and the incisor overjet and overbite were also normal with the exception of the left lateral incisor which was mildly crowded into a lingual crossbite relation. Assessing dental age according to erupted teeth, therefore, was a problem. In view of the presence of 5 maxillary deciduous teeth and the non-eruption of the second molars, dental age would appear to be around 10 years of age. On the other hand, the full eruption of the entire mandibular dentition would suggest 12-13 years.

DDD.Fig._2

Fig. 2. The original and poor-quality panoramic film shows full eruption of all permanent teeth and, judging by the almost completed root formation of the premolars and canines, a dental age approximating to 12 years. Note the over-retention of the deciduous molars and canines in the maxilla.

The panoramic film of the teeth is of poor quality and lacks clarity (Fig. 2). Nevertheless there is much to be learned from it:-

1. Third molars appear to be congenitally absent, although there early signs of a developing follicle on the mandibular right side and possibly on the left side of the maxilla. Aside from these, all permanent teeth are present and in fairly advanced stages of development.

2. As far as can be seen, first permanent molars and incisors have complete root formation with apexification.

3. The premolars and canines appear to be in the final stages of root closure and the second permanent molars still have about one third of their roots to be completed.

a. The second molars have erupted in the mandible in due time and appear to be close to eruption in the maxilla.

b. The eruption of the maxillary premolars and canines is delayed well beyond normal, defining their unexfoliated deciduous predecessors as over-retained.

c. The maxillary deciduous molars, although largely resorbed, are over-retained due to the minor displacement of the path of eruption of the premolar teeth.

d. The roots of the deciduous canines are almost complete with little or no resorption.

e. The unerupted permanent canines are displaced and angulated mesially and their radiographic images are enlarged.

f. The left canine is superimposed on the middle section of the root of the lateral incisor. Together with the degree of its radiographic enlargement, this suggests palatal displacement.

g. The right canine is more horizontally oriented and overlaps the apical section of the root of the lateral incisor. The fact of its radiographic enlargement might also suggest palatal displacement, but at this height in the alveolus, labial displacement is also possible.1

h. The dental age of the patient, based on root calcification, is approximately 12 years of age. 2

It is not that long ago that most of us would have treated this patient on this radiographic evidence alone or with perhaps one or two additional intra-oral views. Indeed there are still a good number of us who undertake treatment of this sort with, what we now must consider to be, inadequate records. Failure of treatment under such circumstances must generate the highest rate of litigation against orthodontists - law suits that are difficult to defend in a court of law, given the imaging techniques that are available to us today.

My colleague considered the location, interdental relations and 3-D orientation of both canines to be inadequately conclusive, justifying referral of the patient for a CBCT scan, at an institute specializing in computerized imaging. 3

For the most part, orthodontists are not very savvy at interpreting the material presented by the CBCT technician and, at least here in Israel, where few of us appreciate the scope of imaging that it is capable to provide, we are prepared to accept whatever the imaging institute presents to us. With cost being a major factor in the equation, we have seen that Israeli orthodontists will usually be happy to settle for a series of radial transaxial cuts around the dental arch and a half dozen 3-D screen shots of a case with an impacted tooth. To my knowledge and in contrast to the trend in the US, no Israeli orthodontists have brought CBCT equipment into their offices for “in house” imaging.

I do not believe this to be a negative development, since it has resulted in the proliferation of purpose-built centers with trained staff. Today, with a population of about 1 million residents, Jerusalem is adequately served by about 8 specialist radiographic and CBCT imaging centers, competing with each other over price, advanced equipment, quality and expertise.

A good CT technician with an up-to-date cone beam unit has the ability to produce CT “slices” in any direction, namely horizontal (axial) cuts i.e. parallel to the occlusal plane, vertical (transaxial) cuts i.e. radially around the dental arch, and coronal cuts i.e. vertical cuts in the coronal plane. Additionally, he/she will be adept at performing 3-D imaging in the form of individual screen shots of the entire dental arch with all the soft tissue and alveolar bone stripped away, to leave just the teeth in place and will usually be able to produce a very instructive 3-D video clip of the jaw in question. 4

DDD.Fig._3

Fig. 3. Four 3-D screen shots offer an excellent way to see the position and relations of the impacted canines and to plan orthodontic movement. The transaxial (vertical) slices show canine-driven root resorption on the distal and lingual side of the middle portion of the left lateral incisor.

My correspondent had referred his patient to an excellent dental imaging center in Israel, in a small town in the North of the country. He sent me two printed pages with transaxial cuts of the anterior maxilla and four 3-D screen shots (Fig. 3), together in a compact disk.


Fig. 4. A dynamic series of cuts in each of the three planes of space, axial (horizontal), transaxial (radial vertical) and coronal vertical and their exact location on the other two planes. (Reconstruction by Amnon Leitner, Panorama Imaging Center, Nahariya, Israel).

The imaging center then augmented this by providing two further items which they produced with superb quality imaging. The first was a video program that simultaneously showed the cuts in one plane and how they are described in the other two planes of space (Fig. 4).


Fig. 5. A beautifully prepared 3D reconstruction video clip of the location, orientation and relations of the impacted teeth to the adjacent teeth. Given the ease of interpretation and accessibility of accurate information in this three-dimensional rotating model, the planning of treatment to resolve the impaction becomes a straightforward and foolproof exercise. (Reconstruction by Amnon Leitner, Panorama Imaging Center, Nahariya, Israel).

The second was the 3-D video clip of the teeth in situ in a revolving mode (Fig. 5). While both are important, the second should sit well with orthodontists insofar as it is precisely the way that the orthodontist sees the erupted dentition in the patient’s mouth in the office, with the enormous added bonus of observing the root orientation of the impacted tooth and its proximity to other teeth. The graphics are very illustrative. They eliminate guesswork and make the diagnostic process virtually guaranteed. Treatment strategy and appliance design are thus greatly simplified, making mistakes less common and failure largely avoidable.

At the same time these views possess the capability for revealing otherwise hidden pathology of the hard and soft tissues, including such lesions as invasive cervical root resorption5 which is a potent factor for failure of response of the tooth to orthodontic traction6 and bucco-lingual root resorption of the incisors.7

Positional diagnosis and treatment strategy for the two impacted canines

On the left side, the unerupted maxillary canine is tipped lingually, but its apex is in a good location in the line of the arch, directly above the apices of the first premolar. At the apical level, there is adequate space between incisor and premolar, but at the level of the crowns of the teeth, there is insufficient space and the premolar is slightly rotated mesio-buccally. Simple space opening is required, which is easiest to achieve with a coil spring. Care should be taken to maintain the incisor and premolar in an upright orientation, so as not to close the inter-apical distance. There will be a tendency for the premolar to rotate further mesio-buccally with the space opening, which will bring the palatal root to the mesial and this may interfere with the canine.8 Accordingly one should deliberately aim to rotate the premolar mesio-lingually before exposing the canine, although the space opening itself may encourage the canine to erupt autonomously. The resolution of the impaction on this side is very straightforward.

On the right side, the problem is far more complex. The lateral incisor root apex is tipped excessively in a palatal direction and is almost certainly palpable under the palatal mucosa. The canine is clearly palatal to the general line of the dental arch and proceeding towards the palatal side of the root of the central incisor, yet it is labial to this lateral incisor root. 9

Theoretically, there is adequate space between first premolar and lateral incisor for the canine to find its place in the arch. The premolar is tipped distally, has 2 labial and one palatal root, is rotated slightly mesio-buccally and, once traction is applied to the canine, this palatal root of the premolar could quickly become an obstacle in the path of the canine. A further impediment is the more horizontal angulation of the canine, with its apex distal to its normal place above the second premolar, but more or less in its ideal bucco-lingual location. Because of its abnormal angulation, its direction of eruption is more and more mesial and it is presently in danger of progressing to the palatal side of the central incisor. This would then present us with the apparent paradox of a palatal canine which is labial to the lateral incisor and palatal to the central incisor! 9

Treatment recommendations were as follows:-

1. Place a full maxillary fixed appliance except for the right lateral incisor, which should be excluded.

2. On each side, the bracket on the first premolar should be placed slightly distal to the mid-buccal position and oriented with its mesial end slightly more coronally angulated. In this way, a straight wire will upright its root to the distal and rotate it mesio-palatally, to distance the palatal root from the path of the canine.

3. Ignore the lateral incisor completely.

4. Create space for the canines on the left side between lateral incisor and premolar and on the right side between central incisor and premolar, leaving the lateral incisor unattached and free. Carefully control the orientation and rotations of the premolars as described above, on a heavy round base arch.

5. Prepare a 0.016” stainless steel labial auxiliary archwire of the design depicted in Fig. 6 and in two websites of this series10, 11, with a horizontal loop for the right canine only.

6. Surgically expose the canines on the labial side of the alveolar ridge. A closed eruption technique should be used. Particularly on the right side, an open exposure will leave the roots of the adjacent teeth bared and later corrective gingival coverage will require separate periodontal procedure and a poorer outcome.12

7. Bond eyelet attachments in vertical orientation, parallel to the long axis of the tooth– no sophisticated bracket, despite what attachment are present on the other teeth.

8. On the left side, you should be able to draw the canine direct to the labial archwire.

9. On the right side, make sure the loop of the auxiliary wire is not too high in the sulcus, because this will cause ulceration of the inner aspect of the lip. Its passive position is horizontal and it should be brought up to the fully replaced flap tissue and ligated by the wire ligature or gold chain that you will have threaded though the eyelet, to hold it against the flap.

10. The flaps should be sutured back to their former position and the teeth completely re-covered.

11. The right canine should start to bulge the soft tissue quite quickly and, when it is in danger of breaking through the oral mucosa, it will be necessary to perform an apically repositioned flap to place attached keratinized gingival tissue high on the crown of the tooth, for the remainder of the alignment.

12. The lateral incisor will then be free of its constricted relationship with the canine and can be bonded with a regular bracket.

13. The auxiliary archwire will be discarded once the canine has moved sufficiently in a buccal direction to be clear of the roots of the adjacent teeth and the tooth may then be drawn down directly to the labial archwire

14. The eyelets should not be removed until both canines and the lateral incisor are fully in the arch, and on a round stainless steel archwire. At this point the degree of torque needed for each of these teeth may be more readily assessed.

15. Substitute regular brackets for the eyelets and go through your leveling, aligning and torqueing archwires again, from round NiTi to rectangular steel, as indicated.

Given the initial class 1 relationships of the teeth and jaws, it is unlikely that much attention will need to be directed to other features of this child’s dentition.

Treatment of similar cases of a palatal canine which is “labial-to-the-lateral-incisor-and-palatal-to-the-central-incisor” have been presented earlier on this website9 and in my textbook. 13

References

1. Chaushu S, Chaushu G, Becker A. The use of panoramic radiographs to localize maxillary palatal canines. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endododontics 1999; 88:511-516.

2. Becker A. The orthodontic treatment of impacted teeth. 3rd edition. Oxford: Wiley-Blackwell Publishers. 2012. Pages 2-5.

3. Chaushu S, Chaushu G, Becker A. The role of digital volume tomography in the imaging of impacted teeth. World Journal of Orthodontics, 2004; 5:120-132.

4. Becker A, Chaushu S, Casap-Caspi N. CBCT and the Orthosurgical Management of Impacted Teeth. Journal of the American Dental Association 2010;141(10 suppl):14S-18S.

5. Becker A, Abramovitz I, Chaushu S. Failure of treatment of impacted canines associated with invasive cervical root resorption. Angle Orthodontist, 2013, 83:870-876.

6. Becker A, Chaushu G, Chaushu A. An analysis of failure in the treatment of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics 2010;137:743-54.

7. Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. American Journal of Orthodontics and Dentofacial Orthopedics 2005, 127: 650-654, quiz 754.

8. Opening space for the canine – it’s not so simple as it seems. Website Bulletin #7 January 2012 http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=211

9. The palatally impacted labial canine. Website Bulletin #16 November 2012 http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=400

10. The third dimension in directional traction of an impacted tooth. Website Bulletin #5 November 2011 - http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=199

11. Canines that resorb lateral incisors – can it be a Win-Win situation? Website Bulletin #18 January 2013 http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=433

12. Becker A, Chaushu S. Palatally impacted canines: The case for closed surgical exposure and immediate orthodontic traction. American Journal of Orthodontics and Dentofacial Orthopedics 2013;143:451-459.

13. Becker A. The orthodontic treatment of impacted teeth. 3rd edition. Oxford: Wiley-Blackwell Publishers. 2012. Pages 430-435.