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Bulletin #13 - July 2012

What is a closed eruption surgical exposure?

It is not the intention in this bulletin to discuss the pros and cons of open versus closed exposure in the treatment of impacted teeth in general. That will be left for another opportunity. Nevertheless, a brief description of the two is essential for an understanding of the differences between them. Both methods have their place and both will produce fine outcomes when their appropriateness for the specific case and circumstances are determined objectively, without being influenced by the introduction of secondary considerations.

In the open eruption technique, the impacted tooth will be open to the oral cavity at the end of the procedure and access to it will be assured, at least in the short term. An attachment may be placed at any time during and after the procedure and often after some spontaneous eruptive improvement to the tooth may have occurred. This provides the most distinct and major advantage of the method, since there if no reason for the orthodontist to be present at the surgical episode. The procedure is a purely surgical undertaking.

At the appropriate time, the orthodontist refers the patient to the surgeon/periodontist, requesting that a specific exposure be performed, depending on the location of the tooth¹. If the impacted tooth is low down in the alveolus and bucco-lingually close to its place in the arch, then a simple “window” technique should be used, in which a small area of overlying gingival tissue is removed, to leave the labial surface of the tooth visible. This will leave the tooth invested with a narrow band of attached gingiva on its labial side.

If the tooth is above the line of the attached gingiva, then this type of exposure would leave the impacted tooth invested labially with thin mobile oral mucosa. In this case, an apically repositioned attached gingival flap procedure² should be performed to circumvent this undesirable outcome.

For a palatally impacted tooth, where its depth under the thick palatal mucosa may be quite considerable, occasionally reaching 10mm or more, the “window” technique usually requires placement of a pack to prevent re-healing of the tissues over the exposed tooth.

In direct contrast, a closed eruption technique leaves the initially surgically exposed tooth re-covered by soft tissue at the end of the procedure.³ Before the surgical flap is re-sutured to its former place, an attachment must be bonded to the tooth, in order for the orthodontist to gain access to and control over the progress of the eruption.⁴

Access to the impacted tooth is provided by the reflection of a wide flap over the immediate buccal or palatal area concerned, the crypt of the tooth identified and a small opening made in the dental follicle to reveal the pristine surface of the crown of the tooth. An orthodontic attachment must be bonded to the tooth at this time and it should be done with the minimum of further exposure of the crown of the tooth and certainly not extended down to the periodontally-sensitive CEJ area. The size of the exposure should be defined as the minimum area needed for the placement of the small attachment, while providing for the blood-, saliva- and water-free environment needed for successful bonding to the acid-etched enamel surface.⁴

Although both the surgery and the bonding can undoubtedly be performed by the attending surgeon, there are compelling reasons for the latter procedure to be carried out by the orthodontist, despite the fact that this makes it incumbent on the orthodontist to be present at the exposure and to take an active part in the procedure. It runs very much against the grain for the orthodontist to actually enter the operating theatre for the express purpose of bonding an attachment to the unerupted tooth and, perhaps, one may be excused for being more than just a trifle skeptical about the veracity of the myriad of objections that most of our orthodontic colleagues offer for not doing so. Nevertheless, as explained elsewhere,⁴ the advantages overwhelmingly outweigh the disadvantages….. the more so when one takes into consideration that it is the orthodontist who will be taken to account in the event of treatment failure and not the oral surgeon.

Unlike the open procedure, therefore, the closed procedure is not solely the realm of the surgeon and the orthodontist has a prominent role to play, the benefits of which he/she will reap in the subsequent orthodontic phase of bringing the tooth into the arch and into alignment. Accordingly, this month’s bulletin is devoted to describing this procedure in some detail, indicating the role of the orthodontist and emphasizing the merit of close cooperation between the two specialists. The only part of the diagnosis and treatment planning that will be discussed here is directly in relation to a patient who displayed a severely displaced and palatally impacted maxillary canine tooth, to the exclusion of other details of the overall orthodontic condition and treatment.

Accurate positional diagnosis

Fig. 1a, b. The panoramic and lateral skull views.

The case concerns a 14 year old girl with a class 1 occlusion and a fully erupted permanent dentition, with the exception of the presence of a left deciduous maxillary canine. The panoramic view (Fig. 1a) shows the left maxillary canine to be impacted high in the maxilla, between the apices of the incisor teeth and the floor of the nose, with its cusp tip reaching the midline raphe. The profile view, seen in the lateral skull film (Fig. 1b), shows the canine crown to be in a continuous direct line with the long axes of the incisors. Neither of these two films gives adequate information regarding the spatial relationship between canine crown and incisor root apices, nor is it possible to see if there has been any incisor root resorption.

Fig. 2a, b. Periapical views taken at different angles for bucco-lingual diagnosis by the parallax (tube-shift) method.

The main aim of periapical films taken from different viewpoints (Fig. 2a, b) in the present context is to define the bucco-lingual location of the crown of the canine, by noting differences in superimposition of the canine crown and the incisor root between the two films.⁵ Because the crown is in the same line as the long axis of the incisors, there is virtually no discernible difference. A second aim of using these films, often ignored, is to detect abnormality in the dental follicle and any loss of integrity in the sharp enamel outline of the canine crown or in the root. No abnormality was seen.

Fig. 3a-c. 3-D stills taken from the CBCT from the labial and from the lingual aspects.

In the absence of important information regarding the accurate 3-D location of the impacted canine, specifically in relation to the incisor roots, a cone beam CT was ordered.^6-8 Stills taken from the CBCT (Fig. 3a-c), both from the labial and lingual sides also contributed information that was not available from the plane films. Finally, the transaxial (vertical) slices (Fig. 4a, b) through the central and lateral incisors indicated the need for a vertical and slightly posterior applied force vector to disengage the canine from the incisors. It was clear from these views that drawing the tooth direct to the labial archwire was an impossible task, since the roots of the incisors obstructed this path.

Fig. 4a, b. Transaxial (vertical) slices from the CBCT through the central and lateral incisors, respectively.

Pre-surgical orthodontics

Typically, the first stage of orthodontic treatment, prior to surgery, involves the leveling, aligning and space opening of the teeth in the maxilla. This was achieved here using initial leveling wires through to a 0.020” round stainless steel main arch and an expanded coil spring. The coil spring was then substituted by a measured length of stainless steel tubing of 0.036” internal diameter, which was shaped into a gentle curve and threaded on to the archwire between the brackets of the lateral incisor and first premolar, to act as a maintainer for the space prepared and to add rigidity to the base arch. A 0.016” auxiliary archwire with a vertical loop opposite the deciduous canine and a vertical offset at its distal end, to permit passive insertion into the additional molar tube, was prepared (Fig. 5a). A few minutes before the surgery was due to begin, this prepared auxiliary was ligated in piggy-back fashion over the main archwire (Fig. 5b, c).

Fig. 5a-c. The orthodontic set-up immediately prior to surgery. Note the vertical loop in the auxiliary archwire and the distal offset bends

Fig. 6a, b. Views at slightly different angles to show the height of the exposed canine, in the vault of the palate in the midline area. Note that the dental follicle of the canine was opened at the target site and only sufficiently to accept the small eyelet attachment. The remainder of the follicle remained undisturbed. Surgery by Prof. Nardy Caspi-Casap.

Closed eruption surgical exposure

The surgeon opened a wide palatal flap from the midline to the second premolar, taking care not to involve the incisive canal, which was difficult in this case because of the proximity of the canine to the midline suture. The reflected flap was sutured to the canine on the opposite side and palatal bone removed until the canine was exposed high in the palate. Figs. 6a, b should permit the reader to gain an impression of the extreme height of the impacted tooth from the different directions from which these two films were taken. Only a small area of the lingual side of the canine was exposed, because of the proximity of the tooth to the root apices of the incisors. If an open exposure were to have been prescribed here, a much wider opening in the palate would have been required and a pack placed. In these circumstances, it would have been impossible to avoid damaging the incisor roots. It is also highly doubtful if the opening would have remained patent, even with the presence of surgical packs and the most likely outcome would have been a loss of access to the canine – with the subsequent need for further surgery.

Bleeding from the underside of the surgical flap and from the bared bony surface of the palate was easily controlled, due at least in part to the adrenaline content of the local anesthetic. Typically there was no bleeding from within the follicle and around the minimally exposed tooth itself. The surgeon then moved to the other side of the operating table and carefully maintained hemostasis with a fine suction cannula, while the orthodontist dried the exposed enamel surface, applied orthophosphoric acid gel, rinsed and dried the tooth surface with a gentle stream of air from the triple syringe, taking care not to splash up blood on to the tooth surface. A very small eyelet attachment already threaded with a twisted stainless steel ligature, was then loaded with composite paste and placed on the resin primer-prepared tooth surface, where it was LED light bonded (Fig. 7).

Fig. 7. The eyelet attachment was bonded to the available tooth surface.

The deciduous tooth was extracted and the palatal surgical flap replaced after first placing a cut in it, to permit the twisted pigtail ligature to exit in mid-palate, opposite the location of the canine, which was hidden from sight by the re-located and re-sutured flap (Fig. 8).

Fig. 8. The deciduous canine was extracted and the flap replaced to cover the entire exposed area of bone of the palate. Because the direction of traction of the canine will need to be directed vertically and slightly posteriorly downward, the twisted steel ligature was drawn through a slit in the flap before suturing.

With the completion of the suturing of the flap, the surgical procedure came to an end. The last remaining function involved activating the vertical loop of the auxiliary archwire, which had been lying passively on the buccal side and out of the way of the surgeon. This was swung palatally upwards, where it was ensnared in the twisted pigtail ligature at its exit point through the replaced flap tissue in mid-palate (Fig. 9).

Fig. 9. With the flap fully replaced and sutured, the vertical loop of the auxiliary archwire was turned inward with light finger pressure by the orthodontist, to be held in place against the palatal tissue by the shortened and turned over twisted steel ligature, before the patient left the O.R.

In this way, the patient left the operating room with light, extrusive, vertical and slightly posterior traction force of excellent range applied to the impacted canine. It was not anticipated that there would be any need for further active orthodontic manipulation of the sore area for at least a month, during which time considerable positional improvement of the canine could be expected.

References

1. 1. Kokich VG. Surgical and orthodontic management of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics, 2004;126:278-83.
2. 2. Vanarsdall RL, Corn H. Soft-tissue management of labially positioned unerupted teeth. American Journal of Orthodontics, 1977; 72: 53–64.
3. 3. Vermette ME, Kokich VG, Kennedy DB. Uncovering labially impacted teeth: apically repositioned flap and closed-eruption tehchniques. Angle Orthodontist, 1995;65:23-32
4. 4. Becker A. The orthodontic treatment of impacted teeth. 3^rd edition. Oxford: Wiley-Blackwell Publishers. 2012.
5. 5. Jacobs SG. Localisation of the unerupted maxillary canine. Australian Orthodontic Journal 1986; 9: 313–316.
6. 6. Becker A, Chaushu G, Chaushu A. An analysis of failure in the treatment of impacted maxillary canines. American Journal of 7. Orthodontics & Dentofacial Orthopedics, 2010;137:743-54.
7. 7. Becker A, Chaushu S, Casap-Caspi N. CBCT and the Orthosurgical Management of Impacted Teeth. Journal of the American Dental Association, 2010;141(10 suppl):14S-18S.
8. 8. Chaushu S, Chaushu G, Becker A. The role of digital volume tomography in the imaging of impacted teeth. World Journal of Orthodontics, 2004; 5:120-132