ABSTRACT
Multidisciplinary management is essential in cases of orthodontic patients exhibiting canines that have failed to erupt timely. The purpose of the article is to present the special considerations in treating such cases so that good tooth alignment and favorable periodontal statues can be obtained. Current knowledge suggests that regardless the technique of choice, non-traumatic surgery, adequate control of gingival inflammation and utilization of minimal orthodontic forces may ensure a higher percentage of success.
Delayed eruption of canines is a frequently encountered problem in orthodontic clinical practice. The main complication involves the increased probability of tooth impaction. Moreover, other unfavorable sequelae may be encountered.
The multidisciplinary management of these cases, involving combined surgical and orthodontic intervention, may permit the traction of such teeth to the dental arch, simulating a physiological eruption pattern. Thus optimal results characterized by correct tooth alignment and good periodontal status can be obtained.1
ETIOLOGY AND COMPLICATIONS OF DELAYED CANINE ERUPTION
The delay in canine eruption may be the result of either local factors such as abnormal size, form or eruption path, supernumerary teeth, over-retained primary teeth, lack of space due to localized or generalized factors, cysts or odontomas,2,3 either general, inherited factors associated with other dental anomalies.4,5 Genetic multifactorial etiology as well as dental age is speculated particularly in cases of palatally impacted canines.6,7
A significant delay in canine eruption is frequently complicated by the possibility of impaction. Maxillary canine impaction is reported to be 1-3% in the general population,8,9 mainly in subjects of caucasian origin and females more frequently than males.10,11 In 80% of the cases the impacted canine is located palatally.12 Impacted canines were found in 9% of Class III patients and 3,3% of Class II division I patients.13
Other complications of delayed eruption involve pulp necrosis, ankylosis and external tooth resorption.4 Using computerized tomography, the extent of the problem of incisors with root resorption due to canines was revealed (12,5%).14,15 As it is not possible to predict when resorption will occur, all impacted canines should be regarded as potentially damaging.16 A labially ectopic canine position may also be accompanied by periodontal problems because of difficulties in oral hygiene or self-cleaning of the tooth. The lack of keratinized tissue that is observed in ectopic canine eruption is regarded as a cardinal predisposing factor for gingival recession mainly because of increased plaque retention or inadequate toothbrushing.17
Such untoward effects may complicate orthodontic therapy,18 create esthetic problems and lead to decrease of periodontal support or eventually to tooth loss. In fact, recession of marginal tissue may occur during orthodontic therapy, as shown by clinical and experimental studies.19-22 In addition, orthodontic movement of the tooth in the proper arch position will not create additional keratinized tissue.22,23 Combined-multidisciplinary surgical and orthodontic treatment of ectopic or impacted teeth may contribute in preventing such undesirable effects.
DIAGNOSTIC CONSIDERATIONS
Clinical and radiographic examination must first substantiate the assumption that normal timely eruption is not to be expected. If it is observed that the tooth has not started to erupt or its eruption has ceased or that orthodontic therapy is unreasonably delayed then surgical intervention must be planned and the tooth position must be verified.24
The exact localization of the tooth is crucial to managing canines that are expected to erupt timely. The information gathered through clinical and radiographic examination is important in determining the feasibility of surgical exposure, verifying the proper access for the surgical approach, planning the correct biomechanical system for the application of orthodontic forces and documenting the extent of any possible root resorption and damage to the adjacent teeth.4
Clinical examination
Clinical inspection and palpation of the alveolar process is recommended.25-27 Important clinical signs are:
* Over-retention of the corresponding primary teeth while the contralateral permanent has already erupted.
* Substantial reduction in the available space for permanent tooth eruption.
* Rotation and inclination of the adjacent teeth. Palatal inclination of 12 or 22 indicates a palatal position of the impacted canine, while a labial inclination of 12 or 22 indicates a labial position.
* A tubercle felt on palpation, when the impacted tooth resides submucosally, or absence of a bulge in the buccal sulcus 1-1 1/2 years before the expected time of tooth eruption. At earlier ages the absence of a canine bulge should not be considered as diagnostic of canine impaction.15
Radiographic examination
Periapical, occlusal and extraoral exposures can be of particular help in verifying the exact tooth position. However, the need for complementary radiographic investigation should always be based on clinical findings so that unnecessary exposure to radiation is avoided.26,28
Periapical exposures
A periapical radiograph can be useful in determining the canine position in the mesio-distal and the occluso-apical direction. If a second periapical film is obtained using one of the methods described later, the buccolingual position of the tooth can be verified also.29
Occlusal exposures
Occlusal radiographs are recommended to determine the position of the involved tooth in the bucco-lingual and mesio-distal direction. Various techniques can be applied in obtaining occlusal radiographs for the purpose of localizing and impacted tooth.27
Extraoral exposures
Conventional extraoral radiographic techniques, such as the frontal and the lateral cephalometric radiograph and the orthopantomogram, may be a valuable aid in determining the position of the impacted canines, particularly in relation to the base of the antral cavity or other anatomical sites.27 In particular, recent investigations have shown that the orthopantomogram can provide adequate information regarding the position of impacted canines, especially in the case of palatal impaction.30,31
The use of computerized tomography (CT) has been proposed in cases of impacted canines presenting particular diagnostic challenges. Apart form providing exact information on the position of the impacted tooth the CT may also reveal possible resorption of adjacent teeth.32,33
Conventional radiographic methods to determine the exact tooth position
Clark’s technique (or parallax method, image/tube shift method, buccal object rule) is considered as the most to be the most popular in determining the position of impacted teeth.25,27,29 The impacted tooth will reside palatally if in the radiographs it is moving in the same direction as the central beam.
The tube shift can be made either in the horizontal or the vertical plane. For horizontal shifts two occlusal radiographs are needed. For vertical shifts, an orthopantomogram and an occlusal radiograph are taken. This is the combination of choice as the orthopantomogram, on which valuable information can be observed, is often taken as an initial radiograph and this combination only requires one additional exposure.25 Although, the vertical shift is highly recommended in the case of palatally impacted canines, in suspicion of buccal impaction further views are justifiable.31
INDICATIONS FOR SURGICAL INTERVENTION
In some cases space management, removal of obstacles and proper management of the primary teeth will frequently facilitate the uneventful eruption of the succedaneous teeth.34 On the other hand, surgical exposure is in
dicated whenever the delay in eruption interferes with the course of orthodontic treatment.3 In the case of the canines, their esthetic, functional and supportive importance dictates that every effort should be made so that they attain their normal position in the dental arch. As a result, most cases of canine impaction present an indication for combined surgical and orthodontic treatment.
Extraction of an impacted canine should be considered only when the tooth is ankylosed, exhibits signs of root resorption and other pathological changes, is malformed or its position is extremely unfavorable (horizontal or reverse) and any attempt of traction could harm the roots of the adjacent teeth.4,35 A recent investigation36 on the radiographic factors influencing the management of impacted maxillary canines showed that it is guided mainly by labio-palatal crown position and their angulation towards the midline. Canines positioned labially and more perpendicular to the midline, are more likely to be removed.
CONSIDERATIONS IN SURGICAL INTERVENTION
Originally, the surgical technique consisted only of a wide resection of the gingival and osseous tissue covering the impacted tooth. This approach was accompanied by surgical problems such as bleeding, difficulty in the placement of the attaching device and, most important, excessive removal of bone and soft tissues. In addition, various periodontal problems have been reported when using this technique, such as gingival recessions,37-40 bone loss,37 decreased width of keratinized tissue,40 delayed periodontal healing41 and gingival inflammation.40
The concomitant periodontal problems prompted for modifications, so that the surgical intervention was less aggressive for the periodontal tissues.35 The simple flap was substituted by a mucosal-periosteal flap, which after bracket bonding,42 was sutured back in its original or in another more apical position.35,37,43
Based on current knowledge, the specific surgical technique selection is mainly determined by the palatal or labial position of the tooth.
Exposure of palatally positioned canines
Exposure of palatally impacted teeth is not usually followed by periodontal complications unless mistakes are made in the forces exerted or the anchorage used.44 Consequently, flap design is thought to be less critical in the cases of palatally positioned canines.45 However, surgical procedures performed should respect the gingival and the osseous tissues as much as possible. Crescini et al1 have reported favourable orthodontic and periodontal results using a closed eruption technique.
Exposure of labially positioned canines
Higher risk is involved in exposing and orthodontically arranging if the unerupted tooth is on the labial side of the maxillary alveolar process. In those cases periodontal and orthodontic manipulations should present apart from the therapeutic, a preventive aspect as well.44 Any mucogingival intervention should aim at maintaining an adequate zone of keratinized tissue.46,47 If this is not done, and the tooth is brought through alveolar mucosa it is likely that gingival recession will occur leaving a periodontally compromised gingival margin.48
The apically positioned flap is a widely used technique in managing labially positioned canines (Fig. 1). Vanarsdall and Corn37 have suggested that this method is not followed by bone loss, or gingival recession after orthodontic therapy. They also underlined the need of an adequate zone of attached gingiva so that tension form the muscles of facial expression predisposing to gingival recession will be avoided.
Closed eruption technique has also been employed in the management of labially impacted teeth when an apically positioned flap is difficult or impossible to perform, i.e. whenever the tooth is deeply impacted or higher than the mucogingival junction. After tooth exposure, a bracket is bonded and the flap is sutured over the crown. A chain or a wire ligature connects the tooth to the archwire. Lasso wires should be avoided whenever possible. It is believed that this method mimics the physiological eruption process and thus renders the best esthetic and periodontal results. Vermette et al48 produced corroborating results in a study comparing the apically positioned flap and the closed eruption techniques. Recently, Quirynen et al49 and Crescini et al1 have reported good periodontal status around maxillary canines following a closed eruption technique and orthodontic treatment.
BASIC PRINCIPLES IN MANAGING UNERUPTED CANINES
Not depending on the technique chosen, one should follow certain general guidelines in surgically exposing canines, if an adequate periodontal result is to be expected.3,4,44
1. Space regaining in the dental arch for the impacted tooth
This space should be slightly larger than the width of the impacted tooth so that not only is it arranged in the dental arch but also attached gingiva may develop normally around its crown. If adequate space cannot be gained by tooth arrangement and first premolar extraction is planned, it should be carried out after we have confirmed, clinically or radiographically, that the impacted canine has started to move and it is not ankylosed. The other teeth should also be aligned so that a stabilizing arch wire can be placed to avoid side effects on the anchorage teeth.
2. Satisfactory plaque and inflammation control prior and after surgery
3. Preservation of the attached gingival tissues
Future muco-gingival problems can be avoided if the flap is created so that it conserves an adequate zone of attached gingiva, using an non traumatic technique and avoiding extra tension during flap raising.46,47,50
4. Limited epithelia tissue removal
Epithelial tissue removal should be as limited as possible so to enable bracket bonding in absence of blood and saliva, otherwise apical migration of the junctional epithelium could occur. Dental follicle remnants can help in creating functional epithelial attachment.
5. Protection of the cemento-enamel juction
No procedure either mechanical (during removal of epithelial tissues) or chemical (during bracket bonding) should affect the area apically to the cemento-enamel junction. Injury to this area has been shown to relate to gingival recession.51 That is the reason for using of small brackets with rounded ends. Moreover, the bracket should be placed near the incisal edge and any resin residues that may irritate periodontal tissues should be removed.
6. Repositioning of the flap
The flap may be sutured back even in contact with the orthodontic appliance using silk surgical sutures that are removed after 7-10 days. Using surgical paste can prove useful especially in cases where the bracket cannot be placed during the exposure procedure, so that epithelial tissue does not cover up the exposed tooth surface.
7. Magnitude of orthodontic forces
The magnitude of orthodontic forces used should be minimal, preferably not exceed 60 grams so that tooth movement is accompanied by migration of the periodontal tissues.
8. Direction of orthodontic forces
Force direction should remote the impacted tooth from the roots of the adjacent teeth.
9. Initiation of orthodontic traction
It is preferable not to apply force on the tooth immediately after surgery, but wait until tissue healing and flap attachment. Otherwise, the risk of post-operative recession exists.
Sometimes, although basic principles have been followed, tooth arrangement is not possible because of ankylosis (Fig. 2).
CONCLUSION
In cases of canines exhibiting significant delay in eruption surgical intervention often is incorporated in orthodontic treatment planning. Despite the technique of choice any surgical intervention should be carried out with respect to the periodontal tissues and knowledge of the dental development and eruption, periodontal anatomy and physiology as well as reaction to orthodontic forces. The aforementioned requi
rements together with adequate control of gingival inflammation and utilization of minimal orthodontic forces may ensure a higher rate of success.
Smaragda Kavadia-Tsatala DDS,1 Lazaros Tsalikis DDS,2 Eleftherios G. Kaklamanos DDS,3 Sossani Sidiropoulou, DDS,1 Konstantinos Antoniades DDS, MD.4
1 Assistant Professor, Dept of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki.
2 Assistant Professor, Dept of Preventive Dentistry, Periodontology and Implant Biology, School of Dentistry, Aristotle University of Thessaloniki.
3 Resident, Dept of Orthodontics, School of Dentistry.
4 Professor, Dept of Oral and Maxillofacial Surgery, School of Dentistry, Aristotle University of Thessaloniki.
FIGURES 1A-L–A case of a labially positioned canine.A-C Photographs before treatment. The presence of an ischemic bulging of the mucosa simplifies diagnosis. D) Surgical incision. E) Flap raising. F) Placement of the etching agent. G) Placement of the bonding agent. H) Bracket placement. I) After the flap has been sutured back, minimal orthodontic forces are exerted on the exposed canine. J-L) Photographs after treatment. The gingival contour of the canine is similar in both sides (Reprinted under permission of Quintessence Publishing Co Inc).
FIGURE 2–A case of an impacted canine that could not be brought to the dental arch because of ankylosis. A) Photograph before treatment. B) Orthopantomogram before treatment. C) Orthopantomogram after surgical exposure and attempt to move the canine to the occlusal level. The adjacent teeth have been intruded as a result of canine ankylosis. D) Photograph after canine extraction and implant placement (Reprinted under permission of Quintessence Publishing Co Inc).
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