Introduction
Interdisciplinary management of impacted teeth represents one of the most important cooperative interactions between oral and maxillofacial surgeons and orthodontists. Most patients requiring exposure of an impacted tooth are referred for surgery by an orthodontist. The diagnostic work is usually assumed by the orthodontist, who will have treatment preferences and abilities based on training and experience. The orthodontist often is dissociated from surgical planning or, conversely, may request inappropriate treatment. By contrast, surgeons usually learn a generic surgical approach for orthodontically managed impactions, and may receive an incomplete didactic background in diagnosis and treatment planning. Orthodontic mechanics are largely opaque to surgeons, and this puts them at a disadvantage in helping to individualize the surgical plan for their comanaged patient. This division of labor, though valuable, can negatively affect the speed and success of postoperative orthodontics.
The purpose of this report is to provide an evidence-based approach for the treatment of impacted teeth that require joint orthodontic and surgical care. Although the focus is on the management of ectopic canines, the principles can be applied to any impacted tooth that needs alignment. This approach is designed to facilitate communication between the oral and maxillofacial surgeon and the orthodontist, and improve the predictability, ease, and success of treatment.
Introduction
Interdisciplinary management of impacted teeth represents one of the most important cooperative interactions between oral and maxillofacial surgeons and orthodontists. Most patients requiring exposure of an impacted tooth are referred for surgery by an orthodontist. The diagnostic work is usually assumed by the orthodontist, who will have treatment preferences and abilities based on training and experience. The orthodontist often is dissociated from surgical planning or, conversely, may request inappropriate treatment. By contrast, surgeons usually learn a generic surgical approach for orthodontically managed impactions, and may receive an incomplete didactic background in diagnosis and treatment planning. Orthodontic mechanics are largely opaque to surgeons, and this puts them at a disadvantage in helping to individualize the surgical plan for their comanaged patient. This division of labor, though valuable, can negatively affect the speed and success of postoperative orthodontics.
The purpose of this report is to provide an evidence-based approach for the treatment of impacted teeth that require joint orthodontic and surgical care. Although the focus is on the management of ectopic canines, the principles can be applied to any impacted tooth that needs alignment. This approach is designed to facilitate communication between the oral and maxillofacial surgeon and the orthodontist, and improve the predictability, ease, and success of treatment.
Incidence and etiology
Studies reporting the incidence of impacted teeth vary considerably in their conclusions, likely due to regional genetic differences, the dental health of the population studied, and interpretation of what constitutes impaction.
Aside from third molars, maxillary canines are the most commonly impacted teeth. There is a 2:1 incidence among females over males and a 2 to 3 times higher likelihood of palatal versus labial impaction. The incidence of maxillary impaction has been reported to be between 1% and 5% in different populations. A lower frequency has been noted among Blacks and Asians and there is a higher occurrence in Greeks and Turks, with European Caucasians somewhere in between. Reports of rates as high as 23.5% may occur in individual orthodontic practices. Even if we assume a 1% to 2% incidence, the number of patients affected is enormous. As pointed out by Dewel, the canine has the longest, most complex eruption path as well as the slowest development time. It should perhaps be no surprise that it is often impacted.
The etiology of impacted canines, especially palatally displaced teeth, is speculative. There are 2 major theories reported extensively in the literature. The genetic theory suggests that impactions are primarily caused by gene mediation, probably polygenic multifactorial inheritance. Although genetic mechanisms are difficult to prove, the presence of familial similarities, gender differences, and the acceptance of gene mechanisms with other dental anomalies argue strongly for a genetic connection.
Alternatively the guidance theory proposes an environmental factor, specifically the lack of normal contact between the lateral incisor root and the erupting canine. It is well known that anomalous and missing lateral incisors are often seen with palatally impacted canines. Furthermore, there is little argument that environmental factors such as crowding, irradiation, endocrine disorders, gingival scarring, and trauma all may cause impacted canines.
It is likely that both genetics and environmental factors cause impacted teeth. However, diagnosis and treatment success in managing impacted canines, as with other health problems, can be strongly influenced by a better understanding of etiology.
Early diagnosis
After the age of 9 or 10 years when patients often first consult with the orthodontist, there are well-established warning signs of potential canine impaction.
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Clinical signs include:
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Absence of the canine bulge with palatal impactions ( Fig. 1 )
Fig. 1 Lack of canine bulge. - •
Peg-shaped or missing lateral incisors
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A constricted maxilla with dental crowding
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Female patients 2:1 higher incidence
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Class I occlusion in the mixed dentition
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Radiographic signs include ( Fig. 2 ) :
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Lateral or central incisor overlapped by the erupting canine
Fig. 2 Radiograph of signs of canine impaction. Peg laterals, overlap lateral roots, retained primary canines, and enlarged follicular sacs. - •
Enlarged follicular sac of the erupting canine
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Lack of resorption of the root of the primary canine
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Presence of impacted mandibular bicuspids
Sajnani and King have developed an early radiographic prediction of impaction based on angulation of the erupting canine to the midline and distance from the occlusal plane on panographs.
Early diagnosis and treatment of canine displacement avoids the potentially serious risk of resorption of incisor roots ( Fig. 3 ). This injury is common, can begin in the early stages of impaction, and may lead to loss of teeth. Retained impacted teeth may eventually cause arch-length discrepancies, ankylosis, compromised orthodontic treatment, and the potential development of significant disorder.
Clinical management of the impacted canine
Interceptive treatment
Interceptive treatment may reduce the incidence or severity of canine impactions. Although inconclusive, some studies have shown an improved spontaneous eruption of developmentally delayed canines when the primary canine is extracted. It is not fully understood why this strategy expedites canine eruption, although removing an obstacle to eruption is the prevailing orthodontic rationale. However, the “Regional Acceleratory Phenomena” may be an underlying contributory factor. This theory, which has gained traction in the orthodontic community, maintains that bone trauma results in physiologic bone remodeling (in this case from the extraction), which can indirectly facilitate regional tooth movement.
Other studies have shown improvement in canine displacement with orthodontic interventions such as palatal expanders, headgear, and distalization mechanics. The success of such orthodontic approaches lend support to the guidance theory or local environment effect on the etiology of canine impaction as discussed earlier.
Surgical management of the impacted canine
Treatment planning for impacted canines is based on an understanding of the etiology. Selection of surgical technique, however, is driven by the location of the affected tooth, the needs of the orthodontist, periodontal concerns, and individual patient factors. As with orthognathic surgery, good communication between the orthodontist and surgeon is critical to successful and efficient treatment.
There are 2 general approaches to the surgical treatment of ectopic canines. Closed-flap forced eruption, whereby the gingival flap is sutured back over the canine after exposure and bracketing, and open exposure, with or without packing or bracketing, to create an epithelialized fenestration or window through the gingiva that leaves the canine visible. Many studies and opinion pieces have been reported supporting one particular surgical approach over another. However, each method offers specific advantages and disadvantages that clinicians should understand, to help in treatment planning and obtaining improved clinical results.
The accepted surgical techniques are outlined here. These methods are discussed and compared more in depth in the following sections, including indications, advantages and disadvantages, orthodontic and surgical preparation, evidence base for decision making, and case reports.
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Closed-flap forced eruption: labial or palatal impactions
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Open passive eruption
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Labial: apically positioned flap
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Palatal: open packing technique
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Open exposure, forced eruption
Closed-flap forced eruption
The closed-flap forced eruption technique is one of the most popular and versatile surgical approaches for canine impaction management ( Figs. 4–7 ).
A gingival crevicular incision is made palatally or labially, and a full-thickness mucoperiosteal envelope flap is elevated over the impacted tooth. The length of the incision is related to the depth of impaction. Palatally, the incision will typically extend at least 2 teeth on either side of the impaction site (see Figs. 4 and 5 ). Division of the incisal nerve on the palate is usually unnecessary. Bone is removed where necessary, and a bracket attached to a gold chain or wire is cemented onto the buccal or lingual of the impacted tooth (see Figs. 6 and 7 ). Most studies recommend avoiding excessive bone removal, which may lead to periodontal defects and gingival recession. Of particular concern is bone removal apical to the cementoenamel junction. With palatal impactions, some clinicians will remove a channel of bone between the root socket of the extracted primary canine and the crown of the impacted canine ( Fig. 8 ). Although designed to expedite eruption, and intuitively attractive, there are no data to either support or refute this practice. However, because orthodontic tooth movement through bone is a slow physiologic process of resorption and remodeling, the value of additional bone removal still needs to be researched before it can be recommended.
The orthodontic bracket can be cemented only after good exposure and moisture control. Extra cement will help resist debonding (for bracketing tips, see the technical section). The flap is closed primarily, and the chain or wire attached to the bracket exits the wound through the incision and is tied to the arch wire. The orthodontist uses the chain or wire to attach springs or elastic thread, which erupts the impacted tooth. Appropriate forces are necessary because excessive orthodontic force will actually slow or stop eruption of the treated tooth owing to hyalinization of the periodontal ligament.
The advantages and disadvantages of a closed-flap forced eruption are summarized in Table 1 .
| Advantages | Disadvantages |
|---|---|
| The impacted tooth can be aligned while it is erupted | Cannot see erupting tooth without a radiograph |
| There are no packings or open wounds | If bracket debonds it requires another surgery to rebracket |
| Labial attached gingiva is maintained | May take longer to erupt canine compared with open forced eruption |
| Less scarring and periodontal concerns | Orthodontists prefer to see tooth during forced-eruption process to help align |
| For palatal impactions, less postoperative pain | Excessive orthodontic force can impede eruption |
Open passive eruption
Open passive eruption, palatal impactions
Open passive eruption requires a fenestration made through the gingiva, and the impacted tooth is allowed to erupt spontaneously through the opening ( Figs. 9–14 ). It is a time-honored approach that has been in use since before adequate composite cements were available for orthodontic bracketing. The theory that the presence of a thick gingival covering (see Fig. 9 ) slows the natural eruption process is appealing because of the observation that gingival fibrosis can lead to delayed eruption. In addition, gingival tissue is flexible and expandable, due in part to the presence histologically of elastic fibers (see Fig. 10 ). It is not known whether the ability of soft tissue to accommodate pressure and expand without breaking open during the eruption process helps to keep an erupting tooth confined. However, this is often the premise when exposing an impacted tooth (with or without bone removal) and allowing it to erupt spontaneously.
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