12 Surgical aids to orthodontics and surgery for dentofacial deformity
Oral and maxillofacial surgery, in the context of this chapter, includes a wide spectrum of procedures ranging from the removal and exposure of unerupted teeth to bimaxillary osteotomies. In planning these procedures, it is essential to involve the specialist orthodontist and the patients themselves from an early stage.
Surgery in the orthodontic patient will often be an integral part of a protracted treatment programme which may, especially in the case of adult fixed-appliance therapy, take 2 years or more to complete. It is essential, at the planning stage of the dentoalveolar surgery, that patients understand (and are willing to comply with) the extent and duration of the proposed therapy.
This prolonged treatment may relate either to the creation of space for eruption or to the application of external mechanical force to stimulate/induce the eruption of malpositioned teeth. Patients with dental indicators of poor motivation such as irregular attendance, high caries rates and inadequate oral hygiene should have appropriate treatment plans. The treatment administered should be simplified as far as possible to reflect the anticipated extent of cooperation from the patient and to expedite any prescribed treatment. Whilst in the past orthodontics has principally been undertaken in adolescents, adult orthodontics is becoming increasingly popular. Any relevant medical history will influence the type of treatment the patient is offered and the mode of anaesthesia.
The interface between oral surgery and orthodontics is difficult to define accurately but relates to those patients whose treatment decisions lie within both specialties. There will always be cases where choices must be made—to recommend orthodontics alone, surgery alone, a combination of the two or whether no intervention should be recommended. Decision-making in complex cases requires a combination of skill and experience and must be taken with the patient’s best interests as the fundamental starting point.
Nowhere is the practice of dentoalveolar surgery and orthodontics more closely related than in the management of unerupted and impacted teeth. The teeth most frequently affected by failure of eruption are generally the last to erupt in a particular series—wisdom teeth, canines and second premolar teeth. The management of third molar teeth is discussed in Chapter 5.
In orthodontic cases it is unusual for patients to suffer any symptoms from unerupted teeth; they are far more frequently noted after clinical examination or as incidental radiographic findings. Careful monitoring of the eruption of the dentition is essential and the general dental practitioner is best equipped to perform this task. The combined oral surgery and orthodontic treatment options for unerupted teeth are threefold: extraction, exposure ± orthodontics and autotransplantation (most frequently of canines). In some cases (e.g. mesiodens when no orthodontics is planned) unerupted teeth may be left in situ. The autotransplantation of teeth is performed far less frequently than it was in the past due to unpredictable results and the reliability of osseointegrated implants and adhesive bridgework.
The timing of extractions or exposure is dependent on the age of the patient and the stage of development of the dentition. The principal treatment decision in the management of unerupted teeth is whether to extract. In general terms the rationale for removal of unerupted/malpositioned teeth resembles that for wisdom teeth (see Ch. 5). The principal indications for extraction are:
Whilst the crowns of these teeth are frequently in communication with the oral cavity, even where the teeth are not directly visible, clinical examination and palpation of the alveolus will often demonstrate a bulbosity associated with crowns of unerupted teeth, thereby giving an indication of their position. Additionally, the inclination of adjacent teeth may give some important clue to the position of the crown of an unerupted tooth. Radiographic analysis, however, is essential to determine the apex position, morphology and pathologies associated with unerupted teeth.
Radiographic assessment of the unerupted tooth will provide several valuable pieces of information in planning its management: stage of tooth development, crown/root morphology and angulation and the presence or absence of local disease. Most orthodontic assessment will include an orthopan-tomogram (OPT) and a lateral cephalometric view. Intraoral views are essential, however, for the management of unerupted maxillary anterior teeth due to the poor definition of the OPT in this region. In this situation, the OPT will usually be supplemented with periapical and/or upper anterior occlusal films. The use of ‘parallax’ analysis, in which two periapical views of the same area are taken from different angles (see Ch. 5), can be useful in determining whether the impacted teeth are buccal or palatal and therefore in planning the surgical approach to the teeth. In radiographic analysis, the stage of tooth development must also be carefully considered because it is inappropriate to expose teeth whose development is incomplete.
The assessment of whether unerupted teeth are suitable for exposure is beyond the scope of this text and should be undertaken in conjunction with an orthodontic specialist. The decision to expose or not, however, is principally based on three factors: the angulation of the unerupted tooth, the depth of impaction and the relationship to other teeth. In general terms there are four treatment options:
The principles of treatment planning are discussed below in relation to the anterior maxillary region but can equally be applied in relation to unerupted teeth at other sites (most commonly mandibular second premolar teeth or even wisdom teeth).
The objective of exposing an unerupted tooth is to move it into a good functional and aesthetic position. In assessing teeth for exposure one of the prime considerations is the available space into which the tooth can erupt. This may be estimated by comparing the crown width of the unerupted tooth with the available space, either directly from the radiograph (with reference to the magnification in the system) or by measurement of the crown width of the contralateral corresponding tooth.
Attempts should be made to retain the keratinized tissues by employing displacement of the attached gingiva with apically or, occasionally, laterally repositioned flaps. The apically repositioned flap retains the mucogingival collar around the tooth and is displaced apically and sutured into place. The bunched gingiva will remodel as wound healing occurs (Fig. 12.1). If the tooth is misaligned, a bracket and gold chain may be etched to the canine to direct its eruptive path appropriately (Fig. 12.2).
Although simple exposure is satisfactory for superficially placed teeth situated close to the surface and impacted in soft tissue alone, most unerupted teeth are located more than 3–4 mm from the oral mucosal surface and the crown cannot be seen completely after raising a flap (Fig. 12.3). As impaction of unerupted teeth usually involves hard tissue as well as soft tissue, all bone covering the tip of the crown as far as the maximum width of the tooth should be carefully removed. If the tooth is superficial and covered by thin bone this can often be undertaken using a scalpel blade. Where bone coverage of the unerupted tooth is more extensive, a small rose head bur or hand-held chisel may be used to clear overlying bone from the crown. Extreme caution must be taken to avoid damaging the tooth crown and the roots of the adjacent teeth. Unnecessary removal of bone should also be avoided. Whilst soft- and hard-tissue exposure of unerupted teeth is in some instances successful, most commonly (and especially in the case of deeply impacted teeth) the created surgical defect will become re-epithelialized if patency is not maintained. The defect is, therefore, packed with an antiseptic gauze dressing or a glass-ionomer cement bonded to the tooth crown in order to inhibit contraction and re-epithelialization (Fig. 12.4). Postoperative antibiotics are seldom indicated unless there is a known increased risk of wound infection, e.g. patients with insulin-dependent diabetes mellitus.
The application of mechanical force to stimulate and guide eruption of buried teeth is frequently necessary because the angulation of the root of an unerupted tooth is frequently unfavourable. This mechanical force may be employed in a number of ways: gold chains, steel or elastic ligatures and even magnets attached to an orthodontic appliance have all been used to induce the eruption. Mechanical traction is indicated:
If the crown tip of a maxillary canine is beyond the midline of the lateral incisor root, spontaneous eruption will not usually occur and mechanical traction will be necessary. Bonding of the bracket to the tooth following its exposure (Fig. 12.5) involves a sequence of etching, washing, drying and bonding similar to that employed in conventional adhesive dentistry. Bonding is best performed in collaboration with an orthodontist to ensure the angulation and position of the bracket is appropriate in relation to the force to be applied to the tooth. During the procedure maintenance of a meticulously dry field is essential and this is facilitated by careful suction and local infiltration of epinephrine-containing local anaesthetic.
Following the bonding, the flap is apically repositioned (see earlier) or may simply be closed as both compare favourably if external traction is to be applied. If traction is not to be applied immediately, the ligatures or chains may be sutured to the mucosa or orthodontic appliance using non-resorbable material. This minimizes any discomfort from the loose chain.
Although bonding could be undertaken as a second procedure following exposure, this results in greater inconvenience and discomfort to the patient. Whilst simple exposures can typically be undertaken under local anaesthesia, bonding (where the procedure is more protracted and requires excellent moisture control in the operative site) is generally best performed under general anaesthesia.
In the past, autotransplantation was a popular treatment for unerupted canine, premolar and even molar teeth but there are some considerable biological problems associated with the technique to be overcome. Although individual studies have suggested clinical and radiographic success rates as high as 80% for the transplantation (at 1–5 years following surgery), most transplanted teeth will develop evidence of root resorption or even ankylosis if they are not root-treated. The success rate of transplantation can be maximized by careful handling of the tooth and preparation of the socket with minimal trauma. Resorption is directly influenced by the extent of trauma to the periodontal tissues on the root surface and care must be taken to minimize this during the removal of the tooth. For this reason, transplantation should be undertaken only on young, medically fit patients and should exclude all teeth which will be difficult to extract or those with hooked apices which will preclude simple elevation.
During the removal of the unerupted tooth only the crown of the tooth should be manipulated with instruments and whilst the socket is being prepared the tooth is ‘stored’ in the buccal or palatal sulcus beneath the flap. When preparing the ‘socket’, bone removal should be undertaken very carefully, with particular reference to not generating heat. A slow-running, well-irrigated bur is the preferred option to achieve this, although some surgeons use small chisels or osteotomes to remove the bone or expand the socket.
The repositioned tooth should be secured free from occlusion and splinted in place, usually by direct bonding using orthodontic brackets or wire and composite. Alternatively a thin vacuum-formed splint can be constructed and cemented in place. Following removal of the splint (usually after 3 weeks) the tooth should be root-filled with calcium hydroxide and reviewed clinically and radiographically at regular 3-month intervals for at least 1 year to check for resorption or ankylosis. Although the technique appears to be reasonabl/>