Orthodontic Treatment of Impacted Teeth. Adrian Becker

surgical elimination of pathology

       Soft tissue lesions

      The subject of benign tumours and cysts is fully discussed in Chapter 14. For the aspect of surgical intervention, let it suffice to mention here that surgery is the first line of treatment that is indicated for these conditions. Immediately after the first tentative diagnosis, surgery is advised, if only for reasons of obtaining biopsy material to confirm the innocence of the diagnosis. Orthodontic treatment should also be considered at that time, although its application should be delayed until after healing of the surgical wound. In the case of cysts, orthodontic treatment should begin after the cyst has been eliminated and after a filling‐in of bone has occurred around the involved teeth. The actual repair of the bony defect will itself improve the positions of grossly displaced teeth. This will be evident in follow‐up radiographs and in the anatomical topography of the alveolar bone in the area. However, the surgical wound may take many months to heal completely. In the interim, supportive preliminary tasks (oral hygiene instruction, caries treatment, motivational education, etc.) may be undertaken, in preparation for the proposed orthodontic treatment. It is worthwhile to begin with achieving positive results from a preventive dental health programme aimed both at eliminating marginal gingival inflammation and at reduction of the incidence of caries.

       Hard tissue obstruction

      In the case of obstructive impaction, logic dictates the removal of the body that is obstructing the natural eruptive potential of the tooth. This is normally performed by the surgeon and often without recourse to adjunctive orthodontics. Although the procedure often succeeds, this course of action is far from foolproof.

      In Chapter 6 we examine the reliability of spontaneous eruption, which results from the different surgical procedures involved in the treatment of impacted incisors. For the present discussion, we must recognize that there is a significant number of cases in which eruption does not occur within a reasonable time‐frame.

Following the removal of the obstruction, be it a supernumerary tooth, an odontome, residual deciduous roots or even an infra‐occluded primary tooth, the position of most unerupted teeth will eventually improve. However, many of these teeth may not erupt without assistance. The failure to erupt may be due to certain factors, including the extent of their displacement, the character of the healing tissues or other factors relating to the erstwhile obstruction.

      A hard tissue body, such as a supernumerary tooth, occupies significant space in the alveolus. A compound odontoma will generally consist of a random mix of dental tissues and, together with its accompanying dental follicle, in many instances occupies even more space. The result is gross displacement of the developing bud of the normal tooth, both in terms of overall distance from its normal location and in the alteration of the orientation of its long axis. The root and/or crown of a tooth of the normal series will likely be deflected, whether mesially, distally, lingually or buccally. It may also be displaced superiorly (in the upper jaw) or inferiorly (in the lower). All these possible deflections will compromise its chances of spontaneous eruption. Cramped circumstances will have developed between the pathological entity and the adjacent teeth and between (a) the entity and the floor of the nose or (b) the lower border of the mandible (see Chapter 13). A further developmental risk is the forming of abnormally shaped roots on otherwise normal teeth. Such an abnormal consequence will itself cause deviated eruption paths and even prevent spontaneous eruption altogether. However, provided that the integrity of their periodontal ligament (PDL) is not compromised and the odontoma extracted, they may be successfully erupted with orthodontic appliances.

      The failure of an impacted tooth to erupt will inevitably disturb the eruption patterns of the adjacent teeth, which, as a result, will then assume abnormal relationships to one another. Such relationships are usually characterized by tipping and space loss. The overall result of this is that this situation creates a secondary physical impediment to the eruption of the impacted tooth.

       Infra‐occlusion

      In Chapter 11 we shall demonstrate in greater detail that infra‐occluded permanent teeth are sometimes ankylosed to the surrounding bone and will consequently not respond to orthodontic traction. For the purposes of this present chapter, it should be briefly noted that the ankylosed area of the root is often minimal and may easily be detached by deliberate, but gentle, luxation of the tooth. This will normally be carried out using an elevator or extraction forceps and is done in such a way as to release the rigid and inflexible connection of the bony union. The aim is neither to remove the tooth from its socket nor even to tear the periodontal fibres (which is inevitable). The purpose is to bring the tooth to a greater than normal degree of mobility.

      A frequent and undesired consequence of this procedure is a re‐healing and re‐attachment of the tooth to its former ankylotic connection. Accordingly, this approach can only be successful if the traction force is applied to the tooth immediately upon luxation and maintained continuously active. The re‐healing of the bone will be modified by a localized microcosm of distraction osteogenesis [17, 18] created by the traction process. It follows that if the traction force is allowed to decay to ineffectiveness (between patients’ visits for adjustments), re‐ankylosis will result and the tooth will stop moving. Accordingly, in order to be effective, the traction must be of sufficient magnitude and range to cause distraction and to remain active between one visit for adjustment and the next.

The principles of the surgical exposure of impacted teeth

      In general, there are two basic approaches to the surgical exposure of impacted teeth: the open eruption technique and the closed eruption technique [19]. A description and comparison of each of these approaches is set out below.

       The open eruption technique

      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,