Enigma of canine impaction.
Impaction of the canine is a condition in which the tooth is embedded in the alveolus so that its eruption is prevented. Canines are considered the corner stone's of the dentition which not only has esthetic benefit but also has important function in the lateral excursive canine guided occlusion which is important to achieve good functional occlusion. The ectopic eruption and impaction of permanent cuspid is a frequently encountered clinical problem. The diagnosis and treatment of this problem usually require the expertise and cooperation of the general practitioner, the pediatric dentist, the oral surgeon and the periodontist, as well as the orthodontist. It is important orthodontically to align impacted canines for various reasons. Impacted cuspids can cause unsightly malocclusion and resorption of lateral incisor roots. Long standing impacted cuspids are associated with resorbtion of their own crowns and can be associated with dentigerous cyst formation (1,2).
THE INCIDENCES & PREVALENCE
The incidences of buccally impacted canines are low, as compared to palatally impacted canines, but shows variable distribution with regard to ethnic origin. The lowest frequency of impacted canines reported in literature relates to the Japanese sample population 0.27%. (Takahama & Aiyarna 1982). In Americans it was 1.4%[Cramer (1929) & 1.57% [Mead 1930), Dachi & Howell (1961) studies revealed 0. 92. of impacted canine among dental radiographs. Ericson and Kurol estimated the incidence at 1.7% impaction are twice as common in female (1-17%) as in male (0.51%) of all patients with maxillary cuspid, it is estimated that 8% have bilateral impactions. The incidence of mandibular cuspid impaction is 0.35% (1-4).
Bishara and associates (1976) Summarized Moyers theory that impaction is caused by
1. Primary causes:
a. Rate of root resorption of deciduous teeth.
b. Trauma of the tooth bud
c. Disturbances in tooth eruption sequence
d. Availability of space in arch
e. Rotation of tooth buds
f. Premature root closure.
g. Canine eruption in to the cleft area in person with cleft palate.
2. Secondary causes
a. Abnormal muscle pressure
b. Febrile disease
c. Endocrine disturbances
d. Vitamin D deficiency.
SEQUELAE OF IMPACTION (2,6)
Shafter et al suggested the following sequelae for canine impaction
a. labial or lingual mal positioning of impacted tooth.
b. Migration of the neighboring teeth and loss of arch length
c. Internal resorption
d. Dentigerous cyst formation
e. External root resorption of the impacted teeth, as well as the neighboring teeth.
f. Referred pain
h. Combination of the above sequelae.
DIAGNOSIS OF IMPACTION (6-11)
The diagnosis canine impaction is based on both clinical and radiographic examinations. Under normal conditions of development the tooth is palpable buccally above the deciduous canine 2 to 3 years prior to in eruption. Ericson and Kurol (1986) evaluate SOS school children between 10 to 12 years of age and they found that 29% of children had non palpable canines at l0 yrs, but only 5% at 11 years, whereas at later stages only 3% had non palpable canine so he suggested the absence of the 'canine buldge' should not be considered as indicative of canine impaction. Therefore for an accurate diagnosis, the clinical examination should be supplemented with a radiographic evaluation.
Although various radiographic exposures, including periapical radiograph, occlusal films, panoramic view, and lateral cephalograms, can help in evaluating the position of the canines.
Periapical films : A single periapical film provides the clinician with a two dimensional representation of the dentition. In other word, it would relate the canine to the neighboring teeth both mesiodistally and superioinferiorly. The preferred means of radiographic localization is the parallax method introduced by Clark in 1910. He used two periapical radiographs and shifted the tube in the horizontal plane. In 1952, Richards appreciated that a vertical tube shift could also be carried out. No major changes then occurred in this techniques until Keyr, in Australia, in 1986 replaced the periapical radiographs with occlusal radiographs. This modification enables a greater tube movement and therefore a greater shift of the image of the image of the impacted tooth. It also ensure that the whole of the tooth is captured on the radiograph with an occlusal radiograph. In 1989 Southall and Gravely discussed the vertical tube shift combination. In the English dental literature and it is now the performed combination of radiographs for localizing impacted maxillary cuspid. In 1999 Jacobs recommended, when using this combination, to routinely increase the vertical angulations for the occlusal radiographs by 100 to achieve a greater image shift.
Extraoral films: Frontal and lateral cephalograms can sometimes aid in the determination of the position of the impacted canine, particularly its relationship to other facial structures (e.g. the maxillary sinus and the floor of the nose. Panoramic films are also used to localize impacted teeth in all three planes of space, much the same as with two periapical films in the tube-shift method, with the understanding that the source of radiation comes from behind the patient; thus the movements are reversed for position.
Kurol (1988) suggested C.T. scan particularly when resorption of the lateral incisor roots were suspected. With C.T. scan clear radiographs may be taken at graduated depths in any part of the human body. This technique allows the elimination of super imposition of structures and obscure image.
Surgical method for exposing the impacted canine
There are numerous surgical methods for exposing the impacted canine and bring it to the line of occlusion, most commonly used methods are
1) Surgical exposure to allow natural eruption to occur (Diabase 1971)-This methods is most useful when the canine has a correct axial inclination and does not need to be up righted during its eruption.
2) Surgical exposure with the placement of an auxiliary. After the surgical exposure of the impacted tooth, an auxiliary is attached to the crown. Such an auxiliary can be directly bonded to enamel.
Three approaches are generally recommended
i. Circular incision (Ernest R sehwarty 1972) created a small window on the labial mucosa to expose the band to which a bracket was welded.
ii. Vanarsdall and Corn 1977 introduced "Apically repositioned flap" technique in this method, the mucogingival flap was raised from the crest of ridge that included the attached gingival. The canine was exposed and the flap then sutured to the labial side of the crown of the canine so as to cover the denuded periosteum and the overlying cervical portion of the crown, while the remaining portion of crown is exposed.
iii. M.C. Bride 1979 proposed full flap closure
procedure : A buccal surgical flap was raised as high as necessary to expose the unerupted canine. An attachment was than bonded to the tooth, and the flap was fully sutured back to its original place. A twisted stainless steel wire that had been threaded through the attachment. Is then drawn inferiorly and through the sutured edge of the reflected flap, at the crest of ridge or through the socket vacated by the extracted deciduous cuspid.
Removable versus fixed appliances: The use of fixed appliances to move the exposed tooth is advocated in most cases. This is because there are certain disadvantages to the use of removable appliances, including the need for patient cooperation, limited control of tooth movement, and the inability to treat complex malocclusions. McDonald et al and Fournier et al suggested the use of Hawley-type appliances designed to transfer anchorage demands to the palatal vault and the alveolar ridge. Such appliances might be useful in patients with multiple teeth missing when the use of fixed appliances is not recommended.
One-arch versus two-arch treatment: Most malocclusions, including those that involve impacted canines, require placement of the orthodontic appliance on both maxillary and mandibular arches. Such an appliance will enable the orthodontist to achieve the desired biomechanical control needed to obtain optimal results.
The mandibular arch is not frequently used as a source of anchorage to move the impacted maxillary canine. This is due to the difficulty encountered in controlling the magnitude and direction of the applied force from the mobile mandibular arch. Therefore such inter arch mechanics should be considered only when the desired forces cannot be applied from within the maxillary arch.
Methods of applying traction--Various methods have been used for moving the canine into proper alignment; these include the use of light wire springs soldered to a heavy labial or palatal base wire, mousetrap loopse bent in the arch wires and rubber bands but with introduction of new orthodontic material such as elastic threads and elastomeric chains, the orthodontist has greater control of force magnitude and direction.
Regardless of the material used, the direction of the applied force should initially move the impacted tooth away from the roots of the neighboring teeth. In addition the following considerations are recommended.
(a) The use of light forces to move the impacted tooth, not more than 2 ounces (60 grams) of force,
(b) Either availability or creation of sufficient space in the arch for the impacted tooth.
(c) Maintenance of the space by either continuous tying of the teeth mesial and distal to the canine or placement of close coiled spring on the arch wire.
(d) Provision by the arch wire of sufficient stiffness to resist deformation by the forces applied to it as the canine is extruded. The added stiffness will minimize the undesirable roller-coaster effect caused by intrusion of the anchor teeth as a reaction to the deflection of a lighter and hence-more flexible arch wire.
BONDING, ATTACHMENTS, EXTRUSION AUXILLARIES (1,2,12,13)
After the surgical exposure of the impacted canines the next step is to bond an attachment to the impacted tooth and connect the attachment to an extrusion auxilliary so that the canine can be extruded.
I. Bonding Materials :
Robert A Miller (1996) uses light cured hybrid compomers for bonding to impacted canines. He says that the use of this reduces the failure rates of conventional composites, which thrive on etching and mechanical retention. The bonding procedure is simple (1) Pumice the exposed tooth (2) Bond according to instructions (3) Apply direct to the base of the attachment, press firmly to remove excess. (4) Light cure the prime and bond direct system. The advantages are it can be used under moisture contamination and in horizontally impacted canines.
Andrian Becker (1998) used Rely-a-bond (Reliance Orthodontic products Inc., Itasca, IC) or Right on (TP Laboratories). A small quantity of bonding paste is placed on the attachment after application of a thin coat of catalyst liquid. The enamel was etched using 37% orthophosphoric acid, dried and liquid catalyst was painted over the tooth surface, then the attachment was pressed firmly against the tooth. After few minutes the bonded attachment was tested for strength, so that a pig tail ligature wire can be tied to it.
II. Attachments used :
* Eyelet welded on band material backed with stainless steel mesh, cut and turned to the size of a small bracket.
* Standard Orthodontic brackets
* Lasso wires
* Threaded pins.
* Orthodontic bands
* Hole drilled on the cuspids tip
* Ligature wires
* Gold Chains
IIII. Auxiliaries used :
* Ballista spring (Jacoby 1979)
* Flexible palatal arch (Becker & Zilberman, 1975, 1978)
* Labial spring auxiliary (Kornhauser et al, 1995)
* Seong-Seng (1983) uses a specially designed Begg Auxiliary.
The Kilroy spring (Dr. Bowman and Dr. Carano 2003 JCO)
Orthodontic Treatment (17,20) :
If we simply place the eyelet on the palatal side of the impacted canines and employ direct traction, the attached surface leaves way and it will simply cause the canine to roll over the root of the lateral incisor, to increase the existing rotation. For many of the impacted canines in this group there is an intimate relationship between the canine crown and the lateral incisor root. The root of the lateral incisor blocks the movement of the canine leading to increase of pressure application over a short period of time causing anchorage loss on the other teeth characterized by a mid line shift from the affected side and resorption of the lateral incisor root. A completely different approach must be used in which the tooth must be first made free from its entanglement with the lateral incisor's root. The most practical manner is to bring the tooth vertically downwards [towards the tongue], out of the palate converting the group 2 in to a group 1 case. It may then be moved directly across the arch such that the disimpaction is made possible in two stages. Hence the movements are first the vertical and second the horizontal. In the literature four types of auxiliaries are used to bring about these desired movements which are needed for the first stage of treatment.
They are :
1. Ballista spring [Jacoby-1979]
2. Active Palatal arch [Becker and Zilberman]
3. Labial auxiliary [Korhauser]
4. Mandibular removable appliance [Orton-1995]
In each of these methods it is necessary to use a base arch wire which is thick enough and is tied to the brackets of all teeth on the labial side. The primary aim of employing this heavy arch wire is to hold the space for the canine in the arch, to resist the secondary distortion of the occlusal plane, to maintain arch form and to provide a base from which force can be directed and applied to the impacted teeth to aid in the orthodontic movement.
The Ballista spring is a unilateral spring of rectangular wire as shown in the diagram above, which is tied in to one of the rectangular molar tube. It proceeds forwards to the future canine area [canine space]. At this point it is bent vertically downwards and terminates in to a small loop. With light finger pressure, the vertical position is turned upwards along the canine space and tied to the pig tail ligature to lie close to the palatal mucosa. In this way torque is introduced in to the horizontal part of the ballista spring, which is resisted to a great extent by the molar. The elasticity of the ballista spring exerts pressure for it to return to its original vertical position which in turn applies extrusive force to the unerupted tooth. If the impacted tooth offers a large resistance to the movement or if the distance to be moved is great, lingual molar root torque may occur, representing a loss of anchorage. To overcome this a rectangular main arch wire or soldered palatal arch may be used.
POST TREATMENT COMPLICATIONS
II] Loss of attachment
III] Alveolar bone resorption
IV] Pulpal and root changes in the adjacent tooth.
It is important to orthodontically align impacted canines because the canines play a vital role in esthetics and guided occlusion. When the mandible moves in latero-trusive positions, there are adequate tooth guided contacts on the latero-trusive [working side] to disocclude the mesio-trusive [non-working] side immediately, this guidance is provided by canines. Hence in order to provide an acceptable lateral and protrusive movement the guidance of canines is important. The canines also enhances esthetics by acting as four pillars of mouth. It is also important to identify impaction early in life, so that the treatment success rate increases. Prior to 1950's most orthodontists referred patients to oral surgeons who would decide if the impacted canines be brought in to dental arch or be extracted, there were no surgical methods other than transplantation by which positive and active alignment of an impacted canine be carried out. Due to this narrow limitations of the surgeon's ability to materially assist these cases of impaction for a better chance of success, the orthodontist have come to play a more dominant role in the initial stages of treatment of impacted canines, by providing the traction that is necessary to encourage this eruption, and in many cases to do so successfully in teeth that were previously felt to have a poor prognosis for eruption.
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(17.) Orton HS, Garvey MT, Pearson MH. Extrusion of the ectopic maxillary canine using a lower removable appliance.Am J Orthod Dentofacial Orthop 1995;107:349-359.
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(19.) Chaushu S, Chaushu G. Lingual appliances, implants and impacted teeth. In: Becker A, editor. The orthodontic treatment of impacted teeth. London: Informa UK Ltd; 2007. p. 229-238.
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Anshu Agrawal , Amit Prakash , Syed Akbar Ali , Gautam Singh 
[1,2&3] Senior lecturer
Department of Orthodontics and Dentofacial Orthopedics Rishi Raj dental college and hospital, Bhopal
 Senior lecturer Department of conservative dentistry Darshan dental college and hospital, Bhopal
Received: October 11, 2013
Review Completed: November 11, 2013
Accepted: December 10, 2013
Email for correspondence: firstname.lastname@example.org
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|Author:||Agrawal, Anshu; Prakash, Amit; Ali, Syed Akbar; Singh, Gautam|
|Publication:||Indian Journal of Dental Advancements|
|Article Type:||Disease/Disorder overview|
|Date:||Jan 1, 2014|
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