Adjunctive Role of Orthodontic Therapy

Vincent G. Kokich

Orthodontic tooth movement may be a substantial benefit to the adult periorestorative patient. Many adults who seek routine restorative dentistry have problems with tooth malposition that compromise their ability to clean and maintain their dentitions. If these individuals also are susceptible to periodontal disease, tooth malposition may be an exacerbating factor that could cause premature loss of specific teeth.

Orthodontic appliances have become smaller, less noticeable, and easier to maintain during orthodontic therapy. Many adults are taking advantage of the opportunity to have their teeth aligned to improve the esthetics of their smiles. If these individuals also have underlying gingival or osseous periodontal defects, these defects often can be improved during orthodontic therapy if the orthodontist is aware of the situation and designs the appropriate tooth movement. In addition, implants have become a major part of the treatment plan for many adults with missing teeth. If adjacent teeth have drifted into edentulous spaces, orthodontic therapy is often helpful to provide the ideal amount of space for implants and subsequent restorations.

This chapter shows the ways in which adjunctive orthodontic therapy can enhance the periodontal health and restorability of teeth.

Benefits of Orthodontic Therapy

Orthodontic therapy can provide several benefits to the adult periodontal patient. The following six factors should be considered:

1. Aligning crowded or malposed maxillary or mandibular anterior teeth permits adult patients better access to clean all surfaces of their teeth adequately. This could be a tremendous advantage for patients who are susceptible to periodontal bone loss or do not have the dexterity to maintain their oral hygiene.

2. Vertical orthodontic tooth repositioning can improve certain types of osseous defects in periodontal patients. Often, the tooth movement eliminates the need for resective osseous surgery.

3. Orthodontic treatment can improve the esthetic relationship of the maxillary gingival margin levels before restorative dentistry. Aligning the gingival margins orthodontically avoids gingival recontouring, which could require bone removal and exposure of the roots of the teeth.

4. Orthodontic therapy also benefits the patient with a severe fracture of a maxillary anterior tooth that requires forced eruption to permit adequate restoration of the root. Erupting the root allows the crown preparation to have sufficient resistance form and retention for the final restoration.

5. Orthodontic treatment allows open gingival embrasures to be corrected to regain lost papilla. If these open gingival embrasures are located in the maxillary anterior region, they can be unesthetic. In most patients, these areas can be corrected with a combination of orthodontic root movement, tooth reshaping, and restoration.

6. Orthodontic treatment could improve adjacent tooth position before implant placement or tooth replacement. This is especially true for the patient who has been missing teeth for several years and has drifting and tipping of the adjacent dentition.

Preorthodontic Osseous Surgery

The extent of the osseous surgery depends on the type of defect (e.g., crater, hemiseptal defect, three-wall defect, or furcation lesion). The prudent clinician knows which defects can be improved with orthodontic treatment and which defects require preorthodontic, periodontal, or surgical intervention.

Osseous Craters

An osseous crater is an interproximal, two-wall defect that does not improve with orthodontic treatment. Some shallow craters (4- to 5-mm pocket) may be maintainable nonsurgically during orthodontic treatment. However, if surgical correction is necessary, this type of osseous lesion can easily be eliminated by reshaping the defect 12,15 and reducing the pocket depth (Figure 51-1) (see Chapter 60). This in turn enhances the ability to maintain these interproximal areas during orthodontic treatment. The need for surgery is based on the patient’s response to initial root planing, the patient’s periodontal resistance, the location of the defect, and the predictability of maintaining defects nonsurgically while the patient is wearing orthodontic appliances.

Figure 51-1 This patient had a 6-mm probing defect distal to the maxillary right first molar **(A).** When this area was flapped **(B),** a cratering defect was apparent. Osseous surgery was used to alter the bony architecture on the buccal and lingual surfaces to eliminate the defect (C and **D).** After 6 weeks, the probing pocket defect had been reduced to 3 mm and orthodontic appliances were placed on the teeth **(E).** By eliminating the crater before orthodontic therapy, the patient could maintain the area during and after orthodontic treatment **(F).**

Three-wall defects are amenable to pocket reduction with regenerative periodontal therapy.¹ Bone grafts using either autogenous bone from the surgical site or allografts along with the use of resorbable membranes have been successful in filling three-wall defects.¹⁴ If the result of periodontal therapy is stable 3 to 6 months after periodontal surgery (Figure 51-2), orthodontic treatment may be initiated.

Figure 51-2 This patient had a significant periodontal pocket **(A)** distal to the mandibular right first molar. Periapical radiograph **(B)** confirmed the osseous defect. A flap was elevated **(C),** revealing a deep, three-wall osseous defect. Freeze-dried bone **(D)** was placed in the defect. Six months after the bone graft, orthodontic treatment was initiated **(E).** The final periapical radiograph shows that the preorthodontic bone graft helped regenerate bone and eliminate the defect distal to the molar **(F).**

Orthodontic Treatment of Osseous Defects

Hemiseptal Defects

Hemiseptal defects are one- or two-wall osseous defects that often are found around mesially tipped teeth (Figure 51-3) or teeth that have supererupted (Figure 51-4). Usually, these defects can be eliminated with the appropriate orthodontic treatment. In the case of the tipped tooth, uprighting^2,5 and eruption of the tooth levels the bony defect. If the tooth is supererupted, intrusion and leveling of the adjacent cementoenamel junctions can help level the osseous defect.

Figure 51-3 This patient was missing the mandibular left second premolar, and the first molar had tipped mesially **(A)**. Pretreatment periapical radiograph **(B)** revealed a significant hemiseptal osseous defect on the mesial side of the molar. To eliminate the defect, the molar was erupted, and the occlusal surface was equilibrated **(C).** The eruption was stopped when the bone defect was leveled **(D).** The posttreatment intraoral photograph **(E)** and periapical radiograph **(F)** show that the periodontal health had been improved by correcting the hemiseptal defect orthodontically.

Figure 51-4 This patient showed overeruption of the maxillary right first molar and a marginal ridge defect between the second premolar and first molar **(A).** Pretreatment periapical radiograph **(B)** showed that the interproximal bone was flat. To avoid creating a hemiseptal defect, the occlusal surface of the first molar was equilibrated (C and **D),** and the malocclusion was corrected orthodontically (E and **F).**

It is imperative that periodontal inflammation be controlled before orthodontic treatment. This usually can be achieved with initial debridement and rarely requires any preorthodontic surgery. After the completion of orthodontic treatment, these teeth should be stabilized for at least 6 months and reassessed periodontally. Often, the pocket has been reduced or eliminated, and no further periodontal treatment is needed. It would be injudicious to perform preorthodontic osseous corrective surgery in such lesions if orthodontics is part of the overall treatment plan.

In the periodontally healthy patient, orthodontic brackets are positioned on the posterior teeth relative to the marginal ridges and cusps. However, some adult patients may have marginal ridge discrepancies caused by uneven tooth eruption. When marginal ridge discrepancies are encountered, the decision as to where to place the bracket or band is not determined by the anatomy of the tooth. In these patients, it is important to assess these teeth radiographically to determine the interproximal bone level.

If the bone level is oriented in the same direction as the marginal ridge discrepancy, leveling the marginal ridges will level the bone. However, if the bone level is flat between adjacent teeth (see Figure 51-4) and the marginal ridges are at significantly different levels, correction of the marginal ridge discrepancy orthodontically produces a hemiseptal defect in the bone. This could cause a periodontal pocket between the two teeth.

If the bone is flat and a marginal ridge discrepancy is present, the orthodontist should not level the marginal ridges orthodontically. In these situations, it may be necessary to equilibrate the crown of the tooth (see Figure 51-4). For some patients, the latter technique may require endodontic therapy and restoration of the tooth because of the required amount of reduction of the length of the crown. This approach is acceptable if the treatment results in a more favorable bone contour between the teeth.

Some patients have a discrepancy between both the marginal ridges and the bony levels between two teeth. However, these discrepancies may not be of equal magnitude; orthodontic leveling of the bone may still leave a discrepancy in the marginal ridges (Figure 51-5). In these patients, the crowns of the teeth should not be used as a guide for completing orthodontic therapy. The bone should be leveled orthodontically, and any remaining discrepancies between the marginal ridges should be equilibrated. This method produces the best occlusal result and improves the patient’s periodontal health.

Figure 51-5 Before orthodontic treatment, this patient had significant mesial tipping of the maxillary right first and second molars, causing marginal ridge discrepancies **(A).** The tipping produced root proximity between the molars **(B).** To eliminate the root proximity, the brackets were placed perpendicular to the long axis of the teeth **(C).** This method of bracket placement facilitated root alignment and elimination of the root proximity, as well as leveling of the marginal ridge discrepancies (D to **F).**

During orthodontic treatment, when teeth are being extruded to level hemiseptal defects, the patient should be monitored regularly. Initially, the hemiseptal defect has a greater sulcular depth and is more difficult for the patient to clean. As the defect is ameliorated through tooth extrusion, interproximal cleaning becomes easier. The patient should be recalled every 2 to 3 months during the leveling process to control inflammation in the interproximal region.

Advanced Horizontal Bone Loss

After orthodontic treatment has been planned, one of the most important factors that determine the outcome of orthodontic therapy is the location of the bands and brackets on the teeth. In a periodontally healthy individual, the position of the brackets is usually determined by the anatomy of the crowns of the teeth. Anterior brackets should be positioned relative to the incisal edges. Posterior bands or brackets are positioned relative to the marginal ridges. If the incisal edges and marginal ridges are at the correct level, the cementoenamel junction (CEJ) will also be at the same level. This relationship creates a flat, bony contour between the teeth. However, if a patient has underlying periodontal problems and significant alveolar bone loss around certain teeth, using the anatomy of the crown to determine bracket placement is not appropriate (Figure 51-6).

Figure 51-6 Before orthodontic treatment, this patient had a significant class III malocclusion **(A).** The maxillary central incisors had overerupted **(B)** relative to the occlusal plane. Pretreatment periapical radiograph **(C)** showed that significant horizontal bone loss had occurred. To avoid creating a vertical periodontal defect by intruding the central incisors, the brackets were placed to maintain the bone height **(D).** The incisal edges of the centrals were equilibrated **(E),** and the orthodontic treatment was completed without intruding the incisors **(F).**

In a patient with advanced horizontal bone loss, the bone level may have receded several millimeters from the CEJ. As this occurs, the crown-to-root ratio becomes less favorable. By aligning the crowns of the teeth, the clinician may perpetuate tooth mobility by maintaining an unfavorable crown-to-root ratio. In addition, by aligning the crowns of the teeth and disregarding the bone level, significant bone discrepancies occur between healthy and periodontally diseased roots. This could require periodontal surgery to ameliorate the discrepancies.

Many of these problems can be corrected by using the bone level as a guide to position the brackets on the teeth (see Figure 51-6). In these situations, the crowns of the teeth may require considerable equilibration. If the tooth is vital, the equilibration should be performed gradually to allow the pulp to form secondary dentin and insulate the tooth during the equilibration process. The goal of equilibration and creative bracket placement is to provide a more favorable bony architecture, as well as a more favorable crown-to-root ratio. In some of these patients, the periodontal defects that were apparent initially may not require periodontal surgery after orthodontic treatment.