Periodontal Status Following Treatment of Impacted Maxillary Canines by Closed Eruption Technique: An Overview and Case Report

Multidisciplinary management is essential when canines of orthodontic patients have failed to erupt in a timely fashion. Delayed eruption of canines is a frequently encountered problem in orthodontic clinical practice, and may have other unfavorable sequelae. The purpose of this article is to present the special considerations involved in treating such cases so that good tooth alignment and favorable periodontal status can be obtained.

The maxillary canine is the second most commonly impacted tooth after the mandibular third molars, and the frequency of its impaction is 50 times greater than that of the mandibular canines. The cuspids are generally the last teeth to erupt in the oral cavity and are adversely affected by¹: the loss of space; over-retained deciduous teeth; and deflection facially or palatally off the lateral incisor.

Although the best treatment alternative for impacted teeth is extraction, this approach does not apply to canines, which present with high esthetic and functional requirements. Therefore, alignment of impacted canines into the arch is the best treatment approach.

The multidisciplinary management of these cases, which involves 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.

A periodontist is often called upon by the orthodontist for the exposure of an impacted tooth, which is essential for successful orthodontic treatment.

Localization of the impacted maxillary canine involves both clinical and radiographic examination.² During the clinical examination, the area should be palpated for the presence of a distinct bulge and/or deflection of crowns—mostly of lateral incisors and premolars.²

Radiographic verification of the crown position is also necessary. While evaluating the position of the impacted canine, radiographs must be assessed to determine the accurate position of the crown. To identify the exact labiolingual position of the crown, the dentist should rely on the buccal object rule, which states that when viewing two adjacent periapical radiographs of the impacted tooth taken at slightly different horizontal angles, the buccal object will move in the opposite direction of the x-ray beam. If the impacted canines are located palatally, the crown of the tooth would move in the same direction as the x-ray beam. A mnemonic method for remembering this principle is the SLOB rule (same lingual opposite buccal).³

Historically, various treatment modalities have been described. In general, there are two basic approaches to surgically exposing impacted teeth^1,2,4: the open eruption technique and the closed eruption technique.

Open Eruption Technique

The open eruption technique was the first method used to uncover impacted teeth. In this method, the tooth is left exposed to the oral environment while surrounded by freshly trimmed soft tissue of the palate or labial mucosa. The open eruption technique may be performed in two different ways, as described below.

1. The window technique involves the surgical removal of a circular section of the overlying mucosa and the thin bony covering. Due to the height of the most labially displaced teeth, the entire surgical procedure is typically possible only above the level of attached gingival in the thin oral mucosa. When done on the palatal side, the edges need to be substantially trimmed back and the dental follicle removed to prevent reclosure of the very thick palatal soft tissue.

2. The second open eruption technique involves the apically repositioned flap. This is a modification aimed at improving the periodontal outcome by ensuring that the attached gingival covers the labial aspect of the erupted tooth. This method, a recognized and accepted procedure in periodontics, was first described in the context of surgical and orthodontic treatment of unerupted labially displaced teeth by Vanarsdall and Corn.⁵

Closed Eruption Technique

The alternative basic approach to surgical exposure is the closed eruption technique. In this technique, an attachment is placed on the canine at the time of exposure and the tissues are fully replaced and sutured to their former place to recover the impacted tooth. This was described by Hunt and McBride.⁶ It is a procedure that can be used regardless of the height of canine. For a buccally impacted canine, a surgical flap is raised from the attached gingiva at the crest of the ridge with suitable vertical-releasing incisions and is elevated as high as is necessary to expose the unerupted canine. An attachment is then bonded to the tooth and the flap is fully sutured back to its former position. The twisted stainless steel ligature wire then placed on the attachment is drawn inferiorly and through the sutured edges of the replaced flap. In this method, the tooth erupts towards and through the area of the attached gingiva, and as such, it very closely simulates normal eruption.

When considering a patient for surgical exposure of a labial or intra-alveolar impaction of a maxillary canine, the following four criteria should be evaluated to determine the correct method for uncovering the tooth.^2,7

First, assess the labiolingual position of the impacted canine crown. If the tooth is impacted labially, then any of the three techniques could be used, because generally there is little if any bone covering the crown of the impacted canine. However, if the tooth is impacted in the center of the alveolus, an excisional approach and an apically positioned flap are generally more difficult to perform, because extensive bone might need to be removed from the labial surface of the crown.

The second criterion to evaluate is the vertical position of the tooth relative to the mucogingival junction. If most of the canine crown is positioned coronal to the mucogingival junction, any of the three techniques described can be used to uncover the tooth. However, if the canine crown were positioned apical to the mucogingival junction, an excisional technique would be inappropriate, because it would not result in any gingiva over the labial surface of the tooth after it had erupted. In addition, if the crown were positioned significantly apical to the mucogingival junction, an apically positioned flap would also be inappropriate, because it would result in instability of the crown and possible reintrusion of the tooth after orthodontic treatment. In the latter situation, a closed eruption technique would provide adequate gingiva over the crown without resulting in reintrusion of the tooth in the long term.

The third criterion to evaluate is the amount of gingiva in the area of the impacted canine. If there were insufficient gingiva in the area of the canine, the only technique that predictably would produce more gingiva is an apically positioned flap. However, if there were sufficient gingiva to provide at least 2 mm to 3 mm of attached gingiva over the canine crown after it had been erupted, any of the three techniques could be used.

The fourth and final criterion to evaluate is the mesiodistal position of the canine crown. If the crown were positioned mesially and over the root of the lateral incisor, it could be difficult to move the tooth through the alveolus unless it was completely exposed with an apically positioned flap. In this latter situation, closed eruption or excisional uncovering generally would not be recommended.

Regardless of the technique chosen, certain general guidelines, as enumerated below, should be followed to achieve an adequate periodontal result in surgically exposing canines.⁸

1. Regain space 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 so that 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 confirming, 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. Achieve satisfactory plaque and inflammation control. This must be done both before and after surgery.

3. Preserve the attached gingival tissues. Future mucogingival problems can be avoided if the flap is created so that it conserves an adequate zone of attached gingiva, using a non-traumatic technique and avoiding extra tension during flap raising.

4. Limit epithelial tissue removal. Epithelial tissue removal should be as limited as possible to enable bracket bonding in the 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. Protect the cemento-enamel junction. 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. That is the reason for using 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. Reposition the flap. The flap may be sutured back even in contact with the orthodontic appliance using silk surgical sutures that are removed after 7 to 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. Consider magnitude of orthodontic forces. The magnitude of orthodontic forces used should be minimal—preferably no more than 60 grams—so tooth movement is accompanied by migration of the periodontal tissues.

8. Consider direction of orthodontic forces. Force direction should separate the impacted tooth from the roots of the adjacent teeth.

9. Initiate orthodontic traction. It is preferable not to apply force on the tooth immediately after surgery, but rather to wait until tissue healing and flap attachment have occurred; otherwise, the risk of postoperative recession exists.

Vermette et al⁴ compared the periodontal and esthetic results after closed eruption and apically positioned flap techniques. They found no significant differences in gingival index, plaque index, pocket depth, and bone level between these two techniques, but they identified significant esthetic differences. With an apically positioned flap, the crown length of the impacted tooth is longer than normal due to apical migration of the gingival margin. The crown lengths of teeth uncovered with closed eruption were similar to contralateral nonimpacted teeth in the same mouth. Second, and perhaps more disturbing, high labial impactions uncovered with an apically positioned flap tend to re-intrude after orthodontic treatment. This is due to the healing of the apically positioned flap to the mucosa adjacent to the impacted tooth at the time of uncovering. As the tooth is erupted into the dental arch, the mucosa is drawn coronally. After orthodontic treatment, this mucosal attachment tends to pull the crown of the tooth apically. This disadvantage was not observed in teeth uncovered with closed eruption.⁴

Becker et al¹ found similar favorable esthetic results in their study of the closed eruption technique for uncovering impacted maxillary central incisors.

Duration of the Surgical Procedure

On the face of it, it would seem that an open exposure should take less time than a closed procedure. However, the results of a recent study have indicated quite the opposite. It seems that a wide tissue flap raised in the close eruption technique improves visibility, permitting easier and quicker exposure of the impacted tooth, thus shortening its overall duration.¹

Initiation of Traction

During the closed surgical technique procedure, the orthodontist bonds an attachment and can immediately apply the eruptive force to the tooth, in contrast to the open surgical eruption technique.¹

Final Treatment Outcome

Over the years, several groups of researchers have studied the post-treatment pulpal and periodontal status following the orthodontic resolution of impacted teeth, particularly in relation to maxillary canines and the open exposure technique. A Norwegian group found an increased depth of periodontal pockets on the distal surface of impacted teeth and bone loss on the mesial side with the open exposure technique.⁹ Further corroboration of good clinical periodontal results seen with closed eruption technique in both buccal and palatal canine cases comes from a study carried out by McDonald and Yap in the United Kingdom.¹⁰

A comparison of open versus closed procedures was undertaken by a Seattle group who used a mixed sample of incisors and canines in their study.¹ With regard to those treated with open surgical technique, they found poorer results in both periodontic measurements and esthetic assessment. For buccal canines, clinical crown length was increased and the gingival margins were uneven and of poor appearance. Loss of attachment and bone loss, along with vertical relapse of the erupted tooth was also noted with the open eruption technique. In contrast to this, they found the clinical crown length and gingival appearance in the closed eruption technique group were similar to those of the control side, with a completely normal periodontal attachment and no post-treatment relapse.^1,9-11

A 19-year-old female patient presented with a chief complaint of spacing between her teeth and wanted the teeth to be properly aligned. On examination, her maxillary left canine was missing and a palpable bulge was present on the buccal side of the canine region (Figure 1).

Intraoral periapical radiographs taken with the SLOB technique confirmed that there was an impacted canine placed labially, with its crown mesially angulated and the tooth almost horizontally impacted. The crown of the impacted tooth was in close proximity to the root of the permanent lateral incisor.

A closed eruption technique was chosen and performed under local anesthesia. A surgical flap was raised from the attached gingiva at the crest of the ridge, with suitable vertical-releasing incisions and it was elevated as high as was necessary to expose the unerupted canine. An orthodontic bracket was then bonded to the tooth (Figure 2 and Figure 3), and the flap was fully sutured back to its former position. The twisted stainless steel ligature wire placed on the bracket was drawn inferiorly through the sutured edges of the replaced flap (Figure 4).

The patient was given oral hygiene instructions that included chlorhexidine rinsing of the mouth for 7 days. One week later, the sutures were removed and the area was evaluated. Alignment of the upper left canine into the arch was achieved within 5 months of treatment (Figure 5). The patient was followed for 1 year and did not show any sign of relapse. Her periodontal condition too remained normal, with mild gingival inflammation seen around the tooth.

Delayed eruption of canines is a commonly encountered problem during orthodontic treatment. It presents a considerable amount of challenge to orthodontists as well as periodontists in terms of treatment planning. A well-planned multidisciplinary approach should be followed for the successful treatment outcome of such cases. Proper localization of canine, correct choice of surgical technique, and optimal orthodontic forces are the keys to good treatment outcome.

Nilesh V. Joshi , MDS

Associate Professor, Department of Periodontics and Implant Dentistry, Bharati Vidyapeeth Deemed University Dental College and Hospital, Navi-Mumbai