|Year : 2016 | Volume
| Issue : 3 | Page : 177-183
Management of impacted maxillary canines using the Kilroy spring: A case series
Anil Sharma1, Upendra Jain2, Amitabh Kallury3, Ritesh Chhajed4
1 Professor, Department of Orthodontics, People's College of Dental Sciences and Research, Bhopal, Madhya Pradesh, India
2 Prof. and Head, Department of Orthodontics, People's College of Dental Sciences and Research, Bhopal, Madhya Pradesh, India
3 Prof. and Head, Department of Orthodontics, PDA, Bhopal, Madhya Pradesh, India
4 PG Student, Department of Orthodontics, People's College of Dental Sciences and Research, Bhopal, Madhya Pradesh, India
|Date of Submission||03-Feb-2016|
|Date of Acceptance||11-Apr-2016|
|Date of Web Publication||14-Jul-2016|
Department of Orthodontics, People's College of Dental Sciences and Research, Bhanpur, Bhopal, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Kilroy Springs are cantilever spring auxiliaries that have been added to orthodontic armamentarium to provide forces to maxillary impacted teeth so as to direct their eruption downward and toward the dental arch. Dr. Bowman had designed and developed these orthodontic auxiliaries to assist in the correction of impacted maxillary canines, one of the most problematic dilemmas in our specialty. The key to dealing with impacted maxillary canines is to provide specific directional forces to insure that these teeth are moved down into the dental arch from the point where they are "stuck" in the jaw. These auxiliaries provide a versatile and predictable biomechanics for the correction of a very complex problem of canine impaction. This article describes three cases to highlight the efficacy of these springs.
Keywords: Cantilever springs, Kilroy springs, maxillary canine impaction
|How to cite this article:|
Sharma A, Jain U, Kallury A, Chhajed R. Management of impacted maxillary canines using the Kilroy spring: A case series. J Indian Orthod Soc 2016;50:177-83
|How to cite this URL:|
Sharma A, Jain U, Kallury A, Chhajed R. Management of impacted maxillary canines using the Kilroy spring: A case series. J Indian Orthod Soc [serial online] 2016 [cited 2019 May 19];50:177-83. Available from: http://www.jios.in/text.asp?2016/50/3/177/186380
| Introduction|| |
Disturbances in the eruption of canine are a frequently encountered clinical problem in orthodontics. The maxillary permanent canine by virtue of its long path of eruption from its initial developmental position to its final position of occlusion is subjected to greater displacement or degree of ectopia that might result in impaction.  A number of theories have been proposed to explain the etiology of palatally displaced permanent maxillary canines. Genetic influences have been attributed to the prevalence of ectopic and impacted maxillary canines. Peck et al. concluded that palatally displaced canines appear to be a product of polygenic multifactorial inheritance.  Furthermore, Pirinen et al. found that palatal canine impactions are genetic and related to incisor premolar hypodontia and peg-shaped lateral incisors.  Some others have favored a "guidance" influence that might be associated with missing, displaced, or peg-shaped maxillary lateral incisors, thereby depriving the developing maxillary canines of sufficient lateral incisor root surface to help guide them into proper position.  An increase of 2.4 times in the incidence of palatally impacted canines adjacent to missing lateral incisors as compared with the general population has been noted. 
Other than the third molars, the maxillary canine is the most frequently impacted teeth in the dental arch. Although the incidence of canine impaction is 1 in 100 in the general population,  the ratio is much higher in orthodontic patients (23.5%).  The Incidence of maxillary canine impactions varies from 0.92% to 1.7%. , Impactions are twice as common in females (1.17%) than males (0.51%). Impacted canines are found palatally in 85% of the cases, with labial position in 15% of cases. ,
Most impacted maxillary canines are asymptomatic and since most often the deciduous canines are over-retained in such cases, the patient may not be aware of the canine ectopia or impaction unless such a condition is diagnosed accidentally by a general dentist on a panoramic radiograph and brought to the notice of the patient. Internal or external root resorption of teeth adjacent to canine is the most common sequelae. It is estimated that 0.7% of the children in the 10-13-year-old age group have permanent incisors resorbed, as a result of canine ectopia. Resorption of lateral incisor root is more common than the central incisor. Lateral incisors are more commonly resorbed palatally and at the mid-root level than at the cervical or apical regions.  Root resorption is not only the most common sequelae of canine impaction but also the most difficult to treat. Although the maxillary lateral incisor root is the most commonly affected by the ectopic eruption of canine, ,, the impacted canine may also cause root resorption of the central incisors. In a study by Bjerklin and Ericson of cases with impacted canines, 38% of the lateral incisors showed root resorption, compared to 9% of the central incisors, but every case of central incisor root resorption also showed root resorption of the adjacent lateral incisor.  Ericson and Kurol found that the more mesially the crown of an impacted canine is located, the lower are the likelihood of its spontaneous correction after the extraction of the deciduous predecessor.  Power and short found that if a canine is angled more than 31° to the midline, its chances of eruption after the extraction of the deciduous canine are reduced  [Figure 1].
|Figure 1: The angular relationship of the ectopic canine long axis to the midline used to predict the severity of ectopia|
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Lindauer et al. developed a method for predicting the spontaneous eruption of the ectopically erupting permanent maxillary canine after extraction of the deciduous canine, based on the location of the impacted canine cusp tip and its relationship to the adjacent lateral incisor.  They divided the canine impaction into four groups: Sector I-IV, with Sector IV representing the most severe impaction. They determined that as many as 78% of the canines with their cusp tips in Sector II through IV were destined to become impacted [Figure 2].
|Figure 2: Sector analysis used to determine the degree of severity of the ectopia|
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Cantilever springs have proven their efficacy in the management of impacted and ectopically erupted canines. Single force systems using cantilever mechanics can be effective in achieving controlled three-dimensional tooth movements.
This article highlights the successful treatment of ectopically erupted and impacted canines using cantilever mechanics.
Management of the impacted canines
Once a frank canine ectopia has been identified, and a comprehensive assessment carried out to localize the canine position, decision on its prognosis for alignment should be made. Factors affecting prognosis include patient cooperation, age, general oral health, position of the canine in three planes of space, angulation of the canine to midline, distance from midline, and relation of canine to adjacent lateral incisors. If these factors are unfavorable, attempting to align such a tooth may prove futile and frustrating and hence should be avoided. Even when the prognosis is favorable, the treatment of these impacted and ectopically erupted maxillary canines can be difficult and time-consuming, depending on the degree of ectopia. Once the orthodontic attachment has been placed on impacted canine, orthodontic traction is applied to move the canine into proper alignment. Various methods have been described for applying traction to the impacted canine. These include:
In addition, Bishara  recommends:
- Application of force in the form of elastic or wire traction
- Cantilever mechanics for the treatment of impacted canines described by Fischer et al
- The Ballista spring for impacted teeth described by Jacoby 
- K-9 spring for alignment of impacted canines described by Kalra 
- Kilroy spring for guiding the eruption of impacted tooth designed and described by Bowman and Carano. 
Cantilever springs with a single direction and point of force application are commonly used for the management of impacted and ectopically erupted canines. These cantilever springs produce forces on the impacted teeth in all three planes of space, but the main forces are vertical (extrusive) and labiolingual, thus pulling the teeth into the dental arch into occlusion. These Cantilever springs are designed to produce a low load deflection rate and a consistent optimal magnitude of force, thus avoiding deleterious effects on the surrounding periodontium and the need for frequent reactivation. 
- Use of light force (<60 g) to move the impacted tooth
- Creation and maintenance of sufficient space within the arch
- The use of base arch wire of sufficient stiffness (0.018" × 0.022") to resist deformation by the tractional forces applied.
This article describes the use of Kilroy springs for the correction of the ectopically erupted and impacted maxillary canines. Bowman has described two variants of the Kilroy spring.
This variant of the Kilroy spring is a constant force module that is slid onto a rectangular arch wire over the site of an impacted tooth. In the passive state, the vertical loop of the Kilroy spring extends perpendicularly downward from the occlusal plane. To activate the spring, a stainless steel ligature is guided through the helix at the apex of the vertical loop, and the loop is directed toward the impacted tooth. The ligature is then tied to an attachment that has been direct-bonded to the surgically exposed tooth [Figure 3]. The Kilroy I spring is commonly used for correcting palatally impacted maxillary canines.
|Figure 3: Kilroy I Spring in its passive state as well as actively tied to the attachment on the palatally impacted maxillary left canine|
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This spring was designed to produce a more vertical than lateral eruptive forces for eruption of the buccally impacted tooth [Figure 4]. Its multiple helices not only increase its flexibility but also increase the likelihood of impingement on the adjacent soft tissue. Consequently, more frequent progress checks are recommended when using the Kilroy II spring.
|Figure 4: Kilroy II spring in its passive state as well as engaged into the buccally impacted maxillary left canine|
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| Case Reports|| |
A 15-year-old postpubertal female patient presented to the clinic for the correction of the palatally erupting right maxillary permanent canine. Clinical examination revealed that the patient had a dolichofacial facial pattern with a straight profile, a prominent nose, and a well-developed chin button. The patient had a bilateral Class-I malocclusion with over-retained maxillary canines in both the quadrants. The upper right permanent canine had erupted ectopically into the palate behind the lateral incisor and was in a crossbite with the lower lateral incisor and canine. The lower arch had an over-retained deciduous second molar in the right quadrant. Radiographic examination with an orthopantomography (OPG) revealed that both the maxillary permanent canines were erupting ectopically. The right canine had erupted into the oral cavity, whereas the left canine was impacted palatally behind the upper left permanent lateral incisor. The impacted canine crown tip was situated apical to the cementoenamel junction of the lateral incisor between Sector III and IV and hence had a poor prognosis for spontaneous eruption after removal of the over-retained deciduous canine. On palpation, the canine bulge could be felt deep in the palate behind the lateral incisor root. Since the crown of the impacted canine was obscuring the lateral incisor root, the extent of damage to the lateral incisor root could not be verified on the OPG at this point, but clinically, the patient was asymptomatic and did not report any pain or hypersensitivity in the left maxillary lateral incisor. The OPG also revealed that the patient had a missing lower right second premolar, no tooth bud or the developing crown was seen below the over-retained deciduous second molar. Since this over-retained second deciduous molar was firm and did not show any sign of root resorption, it was decided to leave it in place without disturbing it. The patient was informed that she will have to eventually go in for a prosthesis when this tooth exfoliates [Figure 5].
Since the patient's profile did not indicate an extraction treatment plan, it was decided to extract the over-retained maxillary deciduous canines and open up spaces in the maxillary arch for the impacted/ectopically erupted permanent maxillary canines by slightly proclining the maxillary anterior teeth. After leveling and alignment, a 19 × 25 SS base arch wire was inserted which carried the Kilroy springs as an auxiliary for aligning the palatally impacted permanent canines [Figure 6].
|Figure 5: Case 1: A 15-year-old female patient with Class-I malocclusion and bilateral maxillary canine ectopia|
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|Figure 6: After adequate space was opened up in the maxillary arch for the alignment of the palatally impacted left permanent canine, it was surgically exposed and a lingual button bonded to the exposed crown. Kilroy spring was then inserted on a 19 × 25 ss base archwire to apply traction to the impacted canine|
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After about 15 months of cantilever mechanics, the maxillary left impacted canine had erupted sufficiently into the oral cavity and had been drawn quite close to the dental arch as the Kilroy spring was exerting an extrusive as well as a bucally directed traction force onto the impacted tooth. At this time, the canines were engaged into the main archwire, and finishing and detailing were carried out with 17 × 25 TMA wire for about 3 months. A good Class-I canine and molar relation were achieved at the end of the treatment. Although the upper incisors had been proclined slightly to gain space for the impacted canines, the proclination was not evident on the face, and the incisors were providing a good lip support. An esthetically pleasing and functionally well-balanced occlusion had been achieved at the end of the treatment. Total treatment time was about 24 months [Figure 7] and [Figure 8].
|Figure 7: Case 1: Patient at the end of the treatment after about 24 months of treatment|
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|Figure 8: Case 1: Pre- and post-treatment lateral cephalogram and orthopantomography showing the treatment progress|
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A 14-year-old female patient presented to the clinic with a Class-II division 1 malocclusion with palatally impacted maxillary right canine and also an impacted mandibular left canine and over retained maxillary right and mandibular left deciduous canines. The patient also had a severe deep bite and a horizontal growth pattern [Figure 9]. Since the patient had a Class-II division 1 malocclusion, it was decided to treat the patient with the extraction or maxillary first premolars. However, initially, only the right maxillary first premolar was extracted to create space for the alignment of the ectopically erupting maxillary right canine which was then exposed surgically and traction applied to it with a Kilroy spring to bring it into alignment. Once the maxillary right canine had been brought into the arch, the maxillary left first premolar was extracted, and the extraction spaces were utilized for retracting the maxillary anterior teeth to reduce the overjet [Figure 10]. At the end of 18 months of treatment, all the teeth had been well aligned in their respective arches, and the overjet has been reduced to achieve a Class-I canine and a Class-II molar relation [Figure 11] and [Figure 12]. The finishing is still in progress to open the bite further and settle the posterior occlusion.
|Figure 9: Case 2: A 14-year-old female patient with Class-II division 1 malocclusion and palatally impacted maxillary right canine and mandibular left canine|
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|Figure 10: Maxillary right first premolar was extracted to create space for the alignment of the palatally impacted maxillary right canine with was then exposed and traction applied to it with a Kilroy spring for erupting the canine and moving it bucally at the same time|
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|Figure 11: Case 2: Patient at the end of treatment with the impacted canines well aligned and finishing in progress|
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|Figure 12: Pre- and post-treatment lateral cephalogram and orthopantomography showing the treatment progress|
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An 18-year-old postpubertal adult male patient presented with a Class-I malocclusion with over-retained deciduous maxillary canines and bilaterally ectopically erupted maxillary permanent canines which had erupted palatally behind the over-retained deciduous maxillary canines and were in a crossbite with the mandibular dentition. The patient had a constricted maxilla with the left quadrant of the maxilla being in a complete crossbite with the mandibular dentition from the lateral incisor onward to the second premolar. The maxillary left and right second premolars were severely rotated [Figure 13].
|Figure 13: Case 3: An 18-year-old male patient having a Class-I malocclusion with ectopically erupted maxillary canines|
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The patient was treated with a nonextraction approach since the expansion of the constricted maxilla and derotation of the maxillary second premolars created adequate space for the alignment of the palatally placed maxillary canines. The over-retained deciduous teeth were extracted, the maxillary arch was expanded with a quad-helix and the maxillary second premolars were derotated to bring them into proper occlusion with the lower second premolars. An adequate space was thus created for alignment of the ectopically erupted maxillary canines into the dental arch. Kilroy springs were than used to provide a buccal traction to the palatally impacted canines. These springs also extruded the canines and brought them into occlusion with the opposing mandibular teeth [Figure 14].
|Figure 14: Case 3: Kilroy springs used bilaterally on a 19 × 25 ss base archwire to align the palatally erupted maxillary canines|
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About 5 months of traction with the Kilroy springs was required to drag the canines buccally into the dental arch after which the brackets were bonded on the canines, and they were precisely aligned into the dental arch. The occlusion was then settled on 17 × 25 TMA wires for about 2 months, and the appliance was debonded after a good Class-I occlusion had been established. The total treatment time of the patient was about 18 months. The patient was put on removable retainers after the treatment had been completed [Figure 15].
|Figure 15: Case 3: At the end of treatment, 18 months after the strap-up|
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| Discussion|| |
The maxillary canines are extremely important teeth. They have a very high esthetic value as they are the determinant of a pleasant smile. The canine eminence provides a unique characteristic to the smile, whereas their high gingival contour helps determine the smile line. ,, Their prominence provides a positive lip support at the corner of the mouth, thus preventing the nasolabial sulcus from becoming too deep.  Its unique shape and color cannot be restored when this tooth is replaced by a premolar thus making the situation quite a challenge. ,,
In addition to their esthetic value, these teeth are extremely important in establishing a functional occlusion. The importance of canine protected occlusion, which disoccludes the posterior teeth on lateral excursion cannot be under-estimated. By guiding the lateral disocclusion of the mandible, the canines protect the temporomandibular joint as well as the remaining teeth. ,, Hence, whenever a canine ectopia is detected, every attempt should be made to bring the canines into their proper position.
When an impacted permanent maxillary canine is detected, the situation will frequently require a coordinated multidisciplinary approach with a team of an orthodontist, oral surgeon, and a periodontist working in close coordination with each other to achieve the best possible result. Such routine procedures are not without occasional morbidity. Damage to adjacent teeth during the orthodontic traction process, compromised periodontal support, decreased alveolar bone support, and soft tissue architecture, and although rare, potential ankylosis or inability to successfully move the impacted canine tooth itself are potential adverse occurrences associated with managing impacted maxillary canines. Hence, before attempting to apply traction to the impacted teeth, a thorough evaluation of its position and its proximity to the surrounding vital structures should be made, and the prognosis of the impacted tooth should be evaluated. A cone beam computed tomography may provide a vital three-dimensional evaluation of the impacted tooth and a more accurate diagnosis of the impaction. Of the many factors affecting the success of interdisciplinary approach to the management of the impacted and ectopically erupted maxillary canines, the three-dimensional force system acting on the impacted teeth is the most important. The traction forces should be applied in such a way that they pull the impacted tooth away from other vital structures on their way down to occlusion thus avoiding damage to the surrounding structures. The cantilever springs are much superior in this respect as the direction of pull can easily be controlled by these springs.
| Conclusion|| |
An ectopically erupting or impacted maxillary canine poses a serious esthetic and functional handicap. Correcting such a situation could be both difficult and time consuming. Hence, a careful treatment planning and an application of a meticulous mechanics can help achieve the desired treatment outcome.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15]