Orthodontic Treatment of Impacted Teeth. Adrian Becker

tissue overlying the crown could satisfactorily still leave 1–2 mm of bound epithelial attachment inferior to the free, movable, oral mucosal lining of the sulcus [7].

Fig. 5.4 (a) A high buccal canine exposed by circular incision in the very wide band of attached gingiva in this patient. (b) The tooth has been brought down together with attached gingiva on its labial side.

      Courtesy of Dr G. Engel.

      By contrast, the palatal mucosa is very thick and securely bound down to the underlying bone. In consequence, following its eruption into the palate of a palatally impacted tooth, no parallel precautions need be taken in order to ensure a good attachment for its final periodontal status [5–7].

      When the window technique is used on the palatal side, the cut edges of the wound need to be substantially trimmed back and the dental follicle usually needs to be removed in its entirety. The aim of this is to prevent re‐closure of the very considerable thickness of palatal soft tissue over the exposed tooth. Additionally, where there is a deeply buried palatal canine, the patency of the exposure will need to be maintained with the aid of a surgical pack.

      The apically repositioned flap technique for performing open exposure is with an apically repositioned flap on the labial/buccal side. This method is designed to improve the periodontal outcome by ensuring, in the final instance, that attached gingiva covers the labial aspect of the erupted tooth. This is achieved by raising a labial flap, taken from the crest of the ridge, and relocating it higher up on the crown of the newly exposed tooth. The method is a recognized and accepted procedure in periodontics and was first described by Vanarsdall and Corn [21, 22] in the context of surgical and orthodontic treatment of unerupted labially displaced teeth. According to these researchers, in the absence of the deciduous canine, a muco‐gingival flap, which incorporates attached gingiva, is raised from the crest of the ridge (Figure 5.1). If a deciduous canine is present, the flap will be designed to include the entire area of buccal gingiva that invests it and the deciduous tooth itself will be extracted. In either case, the canine is exposed by detaching a flap from the underlying hard tissue, some way up into the vestibulum. The flap is then sutured to the labial side of the exposed crown of the permanent canine and will overlie its cervical area and cover the denuded periosteum. The remainder of the crown will be exposed. Subsequent eruption of the tooth will be accompanied by the healing of the gingival tissue. When the tooth takes up its final position in the arch, it will be found to be invested with a good width of attached gingiva.

      The apically repositioned flap method of exposure is best suited to labially/buccally impacted teeth, which are situated above the band of attached gingiva and are not displaced mesially or distally from their place in the dental arch. However, if the case presents with more than a minor degree of mesial or distal displacement, a raised and full‐thickness, soft tissue flap will result in unacceptable denuding of the alveolar bone covering the adjacent tooth and will contraindicate the use of this surgical modality. In order to overcome this, a partial‐thickness surgical flap may be raised, which will then leave the donor area invested with a connective tissue cover [23] to heal over by epithelial proliferation.

      This method of open exposure surgery will cause the tooth to acquire a new gingival margin, originating from the healed, cut edge of gingival tissue, which will move with the tooth as it is drawn down into its place in the arch. However, while the periodontal parameters may be very satisfactory, at the end of treatment the physical appearance of the tissues surrounding the aligned tooth will not have a completely natural look and it will usually be possible, even several years later, to identify the previously affected tooth with ease.

On the basis of the results of the study of Kokich’s group from the University of Washington, relating to exposure on the buccal side of the ridge, the group questioned the justification for continued use of the apically repositioned flap method [24]. Indeed, it is clear that there are grounds for their scepticism, particularly in relation to canines that are more severely displaced. On the other hand, it should be realized that, for the more trivial cases where the tooth is fairly close to its final mesio‐distal position and is bulging the oral mucosa at its junction with the attached gingiva, the application of the apically repositioned flap method may actually eliminate the need for subsequent orthodontic treatment, while producing a good periodontal result.

      Experience has shown that many of these teeth never fully come down to the occlusal level and those that do erupt well may take many months, sometimes stretching to a year or more. This appears to be due to the tendency to relapse, which is engendered by a surgically caused distortion of the mucosal lines in the muco‐gingival area [24]. The overall, final result of this form of surgical exposure may display an unaesthetic gingival contour, requiring remedial grafting [21–25]. If left untreated, buccally palpable unerupted teeth may take many months to break through the mucosa and reach their final positions. The process may be speeded up by performing an apically repositioned flap.

      If the unerupted tooth is very high, an apically repositioned surgical flap would need to be larger than usual, since it will need to involve attached gingiva from the crest of the ridge or the free gingiva of the deciduous tooth, to the height of the labial vestibular sulcus. In such circumstances the procedure is not recommended, since the flap would leave a wide area of periosteum of the labial bony plate unnecessarily exposed to the oral environment. This would result in the need to cover this area with grafts harvested from elsewhere in the oral cavity.

      One convenient, alternative procedure for these very high teeth that we have described is to use the two separate techniques in sequence [26]. This would also be appropriate for conditions such as the labial dilacerated central incisor. The first stage is to use the closed eruption exposure procedure, including attachment bonding, to bring the tooth down until it is well above the attached gingiva, bulging the labial mucosa. Only at that point will the apically repositioned flap be used, with the flap being taken over the incisal edge/occlusal tip of the tooth and sutured on its labial side. The tooth will continue to be drawn occlusally, completely encompassed by firm gingival tissue. In addition, a well‐sutured flap will apply pressure on the labial side of the buccally/labially displaced tooth, which will become a positive influence in moving it lingually towards the general line of the dental arch (see Chapter 15).

      An important advantage of the apically repositioned flap method is that the buccally impacted canine is exposed to the oral environment and remains accessible for attachment bonding. Sometimes the progress of the tooth may be monitored for many months, without orthodontic assistance or appliances, until full eruption has occurred (Figure 5.1). At an appropriate later date, an attachment may be bonded by the orthodontist and active extrusion may subsequently be undertaken.

       The closed eruption technique

      The contrasting approach to surgical exposure is the closed eruption technique. This technique involves an orthodontic attachment bonded at the time of the exposure, with the tissues being fully re‐sutured back to their former place, thereby re‐covering the impacted tooth. The technique was first described by Hunt [27] and McBride [4, 5, 28] and is a procedure that may be used regardless of the height or mesiodistal displacement of the tooth.

      In the case of a buccally impacted tooth, a surgical flap is raised from the attached gingiva at the crest of the ridge, with appropriate vertical releasing cuts, and is elevated as high as is necessary to expose the unerupted tooth. An eyelet or button attachment is then bonded and the flap fully sutured back to its former place [7]. The twisted stainless steel ligature wire (or gold chain, as preferred by some clinicians), which has been tied or linked to the attachment, is then