Читать книгу Orthodontic Treatment of Impacted Teeth - Adrian Becker - Страница 102

Historically, this was the first method used to expose impacted teeth. The tooth was exposed and remained open to the oral environment [20]. Following the removal of the soft tissue and of the bone that covered it, the newly exposed tooth was surrounded by freshly trimmed thick mucosa of the palate or the raw cut edge of the labial/buccal oral mucosa.

The open eruption technique may be performed in several ways but, essentially, these fall into two categories: the window technique and the apically repositioned flap technique.

The window technique involves the surgical excision of a circular section of the overlying mucosa and the thin bony covering. This method is illustrated in the advertising fliers that are distributed widely by companies to market soft tissue laser units. The method has the advantage that it is the simplest, most conservative and most direct method of exposing a tooth, which is palpable immediately under the oral mucosa. It may often be performed using only surface anaesthetic spray or gel. An attachment is immediately bonded to the tooth, enabling orthodontically encouraged eruption to proceed and facilitating complete alignment within a very short time. While this method obviously represents a significant advantage in the treatment of a young patient, the long‐term outcome of the procedure may be characterized by loose oral mucosa on the labial side of the tooth. This is not of attached gustatory epithelium, but rather a mobile, thin, oral mucosa, which does not function well as gingival margin tissue. This situation has been widely documented in the periodontal literature.

It is therefore clear that, in the majority of cases of labially displaced teeth (due to their relative height), this entire surgical procedure is usually inappropriate and contraindicated in relation to the mobile area of the oral mucosa, above the level of attached gingiva. However, if the patient has a very wide band of attached gingiva (Figure 5.4) and a labially impacted tooth is situated well down in this band, a simple removal of the 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.