Bilateral Maxillary Impacted Canines - A Challenge for the Lingual Orthodontic Technique.

Dror Aizenbud, Israel

www.lingualnews.com Volume 1, Number 2, March 2003

Abstract
This case report discusses the management of bilaterally impacted maxillary canines by the lingual orthodontic technique, in a 23-year-old woman with Class I malocclusion. The problems associated with impacted maxillary canines, and the specific biomechanical considerations of the lingual technique intervention, for this patient are discussed.

Introduction
The impaction of maxillary permanent canines is a delicate problem for both its functional and aesthetic implications. It requires the collaboration of the oral surgeon and the orthodontist. The orthodontist should have the primary responsibility of coordinating these efforts to provide the patient with the optimal treatment options and the most stable and favorable outcome(1).
Maxillary canines have the longest period of development, the deepest area of development, and the most difficult path of eruption of all the teeth(2). Their normal age of emergence is between 11 and 12 years (3). Other than the third molars, the maxillary canines are the most likely to remain unerupted or impacted. They are also the teeth that most commonly require surgical exposure and orthodontic guidance during eruption(2). Maxillary canine impactions are more common in females (1.17%) than in males (0.51%)(4). The frequency of maxillary canine impaction is significantly higher than that of mandibular canines(5). Impacted maxillary canines are also situated palatally more frequently than labially(6-7). Eight percent of patients with impacted maxillary canines have bilateral impactions(4). The incidence of impacted canines in patients over 20 years of age has been documented as 0.9%(8).
The treatment of adult patients with unilateral or bilateral impacted canine requires an aesthetic treatment approach, which meet their expectations. The placement of orthodontic brackets on the lingual aspect of the teeth offers an alternative to the conventional, i.e., buccal, placement of fixed orthodontic appliances. The lingual technique is prefered to avoid the unattractive appearance of conventional orthodontic appliances (9), and it is more successful in meeting esthetic requirements because the appliance is invisible. The therapeutic outcomes are similar with both techniques, although the lingual requires special biomechanic consideration especially in the case of impacted canine (10-12).

Diagnosis and etiology
A 23-year-old woman arrived to my office, for orthodontic treatment with the chief complaint of impaired facial esthetics due to spaces in the upper frontal teeth, over extruded central incisors and retained upper deciduous canines.

She had a grossly symmetric, mesencephalic face with a well balanced skeletal as well as soft tissue profile and competent lips (Fig 1).

Fig 1: Pretreatment facial photographs

Intraoral examination (Fig 2) showed spaced upper and lower arches, with unerupted permanent maxillary canines and bilateral retained primary maxillary canines. The absence of canines' buccal bulges and the presence of a bilateral palatal bulge were noted upon intraoral palpation.

Fig 2: Pretreatment intraoral photographs

In occlusion, she had a 40% overbite and a 3-mm overjet. The molar relationship was class II in the right side and class I on the left side. The dental midlines were concordant with each other and with the face, and no mandibular shift was detected on closure. There were no signs or symptoms suggesting temporomandibular joint disorders, and the maximum incisal opening and jaw movements were in the normal range. There was no relevant history of any medical problem.

Radiographic examination (Fig 3) showed that all teeth, including the third molars, were present.
Both maxillary canines had well developed roots. The right maxillary impacted canine were mesially angulated near the roots of the maxillary lateral incisors. It had a mesial angle to the midline exceeding 40°.
The maxillary left canine was positioned occlusally and was less severely mesioangulated than the right.

Fig. 3: Pretreatment panoramic, cephalometric, upper occlusal and periapical radiograph of bilateral maxillary impacted canines

Treatment Objectives
The objectives of orthodontic treatment for the patient were to erupt the paltally impacted maxillary canines, level and align the arches, obtain normal overjet and overbite, and achieve a well-intercuspated bilateral Class I canine and molar occlusion.

Based on the patient's overall analysis and soft tissue profile, it was determined that a nonextraction orthodontic treatment plan would be the best approach. In the interdisciplinary treatment plan formulated to meet these objectives, it was decided to expose the canines surgically and bond attachments to aid their eruption with light forces. The lower arch would not be bonded.

According to patient demand, an esthetic lingual fixed orthodontic appliance will be utilized.

Treatment Alternatives
Considering all aspects of the case in detail, during the treatment-planning interview, the patient was told that the canines might not respond to orthodontic eruption; then, they would need to be extracted, and prosthetic rehabilitation with implants or bridgework would be required. She chose orthodontic eruption, and informed consent was taken to this effect.

Treatment progress
Lingual appliance attachments (Ormco 0.018 inch slot) were placed on the maxillary incisors premolars and first and second molars. 0.014 inch NiTi and 0.016 inch NiTi round arch wires were used to start aligning the anterior and posterior segments. (Fig 4). Spaces for the eruption process of the impacted canine were created by gathering up existing space in the arch, particularly in the incisor region. 0.016 inch SS round arch wire, and NiTi open coils springs were used. (Fig 5).

Fig. 4. Alignment of anterior and posterior segments by lingual technique

Fig. 5. Periapical radiographs of spaces created for maxillary permanent canines eruption

Later on consolidation of the entire arch into a composite anchor unit, achived using a heavy 0.016x0.022 inch rectangular SS arch wire. Bilateral maxillary deciduous canines were extracted in the beginning of the surgical exposure intervention.

A mucoperiosteal full thickness palatal flap was elevated between the upper first premolars of both sides. The surgical exposure was very conservative. Minimal bony tissue over permanent canines crown was excised
Then the dental follicle was gently excised and a small area of the upper canine crown was exposed. (Fig 6). After the application of orthophosphoric acid (37 %) for 40 second, the primer was applied immediately. Then a lingual buttons were attached by a self-curing orthobonding (Rely-a-bond, Relaience Co.) to the palatal side of both permanent canines' crown. A soft 0.012 inch ligature wire was twisted around the lingual buttons prior their bonding to canines.
The twisted ligature strands from the maxillary canines were rolled up into a small pigtail loop, close to the palatal mucosa.
The surgical flap closure was carefully done to avoid a poor periodontal mucosal attachment.
This one-step approach is preferable to assure good bonding to the enamel. In this way orthodontist can be directly impressed by the exact position of the impacted canine and planes the best successful way of its eruption into dental arch.
We consider this light and least traumatic surgical exposure to be beneficial to the future periodontal health.

After a week the suture and the surgical dressing were removed, bilateral artificial acrylic canines teeth were applied to the area of the exposure.

The artificial acrylic canine was connected to 1.1 inch bar soldered to first upper molar band on each side separately (Fig 7). The bar was designed to follow the palatal cervical line of the premolar crowns, gingivally to the lingual brackets but not touching the palatal mucosa.

Fig. 6. A conservative surgical exposure and attached lingual
button with a 0.012 inch twisted ligature wire.

Fig. 7. Palatal and buccal views of artificial acrylic canine soldered to first upper molar band on each side separately.

This design is superior to the Transpalatal or Nance appliances, which may touch the fresh palatal flap.
This separated artificial tooth could be easily removed if required during treatment steps or canine eruption process by removing upper molar band.
The pigtail twisted ligature strand loops from the maxillary canines were lightly tied with elastic threads to a continuous auxiliary spring placed on the lingual side of the arch to produce the vertical and palatal traction needed.
The auxiliary incorporates a double vertical loops with a small helix sited at its extremities, which is located opposite the prepared bilateral canines space in the arch and pointing downward and at right angles to the plane of the occlusion (13).

 The spring auxiliary (Fig 8) is tied into all the brackets in, "piggy-back" fashion, alongside the heavy base SS arch wire 0.016 x 0.022 inch already present in the same bracket. The maximum force level of the traction on the maxillary canines was kept below 60 grams/2 ounces per side. After repeated activation with light forces, periapical radiographs were taken to monitor progress.

Within the next 6 weeks, it was noted that the gingiva covering the maxillary left canine was becoming blanched and it was the first to erupt Right canine was erupted 6 weeks later. The maxillary left canine which was in a reasonably good position had moved closer to the occlusal plane than the right one (Fig 9).

Fig. 8. Auxiliary spring for bilaterally canine traction tied in "piggy-back" fashion. Note also the artificial soldered canines.

Fig. 9. Eruption of maxillary impacted canines

After eruption a Nance button appliance was inserted and artificial acrylic canines were removed . Right and left canine lingual brackets that were bonded in a temporary position transferred the lingual buttons.
Upper canines were ligated to an 0.014 inch NiTi round arch wire, because it was important to move the canine crown occlusally and labially. Therefore this arch wire did not include the typical lingual arch wire "mushroom shape" between canines. It was inserted in, "piggy back" fashion, alongside the heavy base arch wire 0.016x 0.022 inch SS already present in the same bracket with the typical "mushroom shape" (Fig 10).
Leveling and aligning of upper arch was progressed by 0.016 inch round SS arch wire and finishing achieved by 0.016x 0.022 inch SS arch wire.
A bilateral Class I well-intercuspated occlusion with ideal overjet and overbite was achieved 6 months later.
Retention was instituted with maxillary Essix retainer. Total active treatment time was 20 months.

Treatment results
There was a remarkable improvement in the occlusion with the eruption of the impacted canines. The mild deepbite Class II malocclusion was corrected and a solid Class I well-intercuspated occlusion with ideal overjet and overbite achieved (Fig 11).

Fig 11: Posttreatment intraoral photographs

Significant improvements in the patient's face and smile were noted. (Fig 12). 

Fig 12: Posttreatment facial photographs

A comparison of the pretreatment and the posttreatment cephalograms (Table 1) showed that the maxillary incisors were mildly proclined during treatment. Overall, the patient's skeletal pattern was not altered by mechanics.
The posttreatment panoramic view showed the roots of the teeth in both arches to be well angulated and aligned (Fig 13). No apical root resorption was detected on radiographic examination, and all anterior teeth, including the canines, registered a vital response to electric pulp testing. Periodontal health was not compromised.
Both the canines at the end of treatment had good periodontal conditions.
She has been in retention for more than 24 months, and the occlusion has been maintained very well during this time.

Table 1:. Pretreatment and postreatment cephalometric measurements

www.lingualnews.com 
Adult and Lingual Orthodontics
EDITORS:
Dr. Silvia Geron D.M.D., M.Sc
Dr. Rafi Romano D.M.D., M.Sc
Dr. Pablo Echarri D.M.D., M.Sc

References

1. Bishara SE Clinical management of impacted maxillary canines. Semin Orthod 1998;4:87-98.

2. Jacoby H. The etiology of maxillary canine impactions. Am J Orthod 1983;84;125-32.

3. Hurme VO. Ranges in normalcy of eruption of permanent teeth. J Dent Child 1949;16:11-5.

4. Bishara SE. Impacted maxillary canines: a review. Am J Orthod Dentofacial Orthop 1992;101:159-71.

5. Shroff B. Canine impaction: diagnosis, treatment planning and clinical management. In: Nanda R, editor. Biomechanics in clinical orthodontics. Philadelphia: WB Saunders; 1996. p. 99-108.

6. Bednar JR, Wise RJ. The management of unerupted maxillary cuspids. Orthod Dialogue 1992;4:1-4.

7. Fournier A, Turcotte J, Bernard C. Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982;81:236-9.

8. Dachi SF, Howell FV. A survey of 3874 routine full-mouth
radiographs. Oral Surg Oral Med Oral Path 1961;14:1165-9.

9. Gorman JC. Treatment with lingual appliances: the alternative for
adult patients. Int J Adult Orthodont Orthog Surg 1987;2:131-49.

10. Gorman JC. Treatment of adults with lingual orthodontic appliances. Dent Clin North Am 1988;32:589-620.

11. Fillion D, Leclerc JF. L'orthodontie linguale: pourquoi est elle en progr?s? (Lingual orthodontics: why is it progressing?) Orthod Fr 1991;62:793-801.

12. Gorman JC, Smith RJ. Comparison of treatment effects with labial and lingual fixed appliances. Am J Orthod Dentofacial Orthop 1991;99

13. Kornhauser S, Abed Y, Harari D, Becker A. The resolution of palatally impacted canines using palatal-occlusal force from a buccal auxiliary Am J Orthod Dentofac Orthop 1996;110:528-34