Orthodontic intervention to resolve periodontal defects: An interdisciplinary approach.

In the new era of esthetics, Orthodontic therapy has gained tremendous acceptance by adults. However,treating adults is more challenging as they present with multiple periodontal problems compromising orthodontic treatment. Hence, to provide optimal treatment to adult patients an active interaction between orthodontist and periodontist is imperative.This article addresses the dilemmas encountered during the treatment of orthodontic patients with periodontal defects.

Dentistry, today is witnessing a rapid shift toward a soft tissue paradigm making it imperative for a clinician to accept this new era of esthetics, and together, joining hands with other specialists to optimize the treatment outcome.

This shift may primarily be attributed to the soaring number of adults with esthetic consciousness, hence expanding the spectrum of orthodontic patients. Treatment for adults is now the fastest growing area in Orthodontics. However, adults seeking orthodontic treatment present with a different set of challenges, such as uneven gingival margins, missing papillae, and periodontal bone loss, requiring an inevitable and a careful co-ordination with a periodontist.

Periodontal defects in adult orthodontic patients can be resolved at various stages of orthodontic therapy depending on the type of periodontal problem. Before orthodontic bracket positioning, it should be determined as to who would be responsible for correcting the periodontal problem.

This article deals with the various periodontal conditions that can be treated in adjunction with orthodontic therapy. The periodontal problems can be broadly categorized as follows:

Soft tissue defects

Gingival margin discrepancies

Missing papillae

Mucogingival defects

Hard tissue/bony defects

Interproximal craters

One-, two- and three-wall defects

Furcation involvement

Horizontal bone loss

Gingival margin discrepancies

Gingival margin discrepancies may be caused by abrasion of the incisal edge or the delayed migration of the gingival tissue. The clinician must determine the cause to decide the optimum treatment, that is, orthodontic movement to reposition the gingival margin or surgical correction of gingival margin discrepancies.

Four easy criteria can help the clinician make an educated choice.[1] The first step is to evaluate the labial sulcular depth over the two central incisors. If the clinically shorter tooth has a deeper sulcus, excisional gingivectomy may be appropriate to move the gingival margin of the shorter tooth apically. However, if the sulcular depth of the short and long incisors is equivalent, gingival surgery will not help. The next step is to evaluate the relationship between the clinically short central incisor and the adjacent lateral incisors. If the shortest central is still longer than the lateral incisors, the other possibility is to extrude the longer central incisor and equilibrate the incisal edge. This will move the gingival margin coronally and eliminate the gingival margin discrepancy. However, if the shortest central incisor is shorter than the laterals, this technique would produce an unesthetic relationship between the gingival margins of the central and lateral incisors. The fourth step is to determine if the incisal edges have been abraded. This is best appreciated by viewing the teeth from an incisal perspective. If one incisal edge is thicker labiolingually than the adjacent tooth, this may indicate that it has been abraded, and the tooth has overerupted. In this situation, the best method of correcting the gingival margin discrepancy is to intrude the short central incisor. This method will move the gingival margin apically and permit restoration of the incisal edge.[23]

Missing papillae

The missing papilla leading to a space above the interproximal contact of the central incisor may be caused by one of two factors. The first possible cause is diverging roots of the maxillary central incisors. This can be corrected by placing brackets perpendicular to the long axis of the central incisor. As the roots align, the contact point lengthens and moves apically toward the papilla.

A second possible cause of space above the interproximal contact of central incisors is abnormal tooth shape. In some patients, the crowns of the centrals are much wider at their incisal edge than at the cervical region. In these situations the contact between the incisors is located in the incisal 1 mm between the two centrals. This is an unusual contact relationship. Most contact areas between central incisors are 2-3 mm long. The best method of correcting this problem is to recontour the mesial surfaces of the central incisors. The amount of enamel that must be removed from each tooth is equal to half the distance between the mesial surfaces of the incisors at the level of the tip of the papilla. Usually this will be approximately 0.5-0.75 mm and does not penetrate into the dentin. After this diastema has been created, the space between the teeth is consolidated. As this occurs, the contact is lengthened and moved toward the papilla.[4]

Mucogingival defects

It has been recommended that in areas that have functionally inadequate width of attached gingiva, a grafting procedure to increase the gingival dimension should precede the initiation of orthodontic therapy. There are consequently two aspects to be discussed in relation to the effect of orthodontic tooth movement on the mucogingival complex, namely:

Alteration in gingival dimensions and the requirement of a certain gingival width for the maintenance of the integrity of the periodontium; and

Changes in the position of the soft tissue margin and the development of soft tissue recessions.

Experimental studies have shown that the labial bone will re-form in the area of a dehiscence when the tooth is retracted toward a proper positioning of the root within the alveolar process.[56] It is therefore likely that the reduction in recession seen at a previously prominently positioned tooth, which has been moved into a more proper position in the alveolar process, is also accompanied with bone formation.

Lingual tooth movement will result in an increased buccolingual thickness of the tissue at the facial aspect of the tooth, which results in coronal migration of the soft tissue margin (decreased clinical crown height). Consequently, in cases with a thin (delicate) gingiva caused by prominent position of the teeth, there is no need for a gingival augmentation procedure in advance of the orthodontic tooth movement. Neither, in the case of a recession type defect should a mucogingival surgical procedure, aimed at root coverage, be performed before the orthodontic therapy. The recession, as well as the dehiscence, will decrease as a consequence of the lingual movement of the tooth into a more proper position within the alveolar bone, and if still indicated at that time, the surgical procedure will have a higher predictability of success than if it was performed before the tooth movement. Facial tooth movement, on the other hand, will result in a reduced buccolingual tissue thickness, and thereby a reduced height of the free gingival portion and an increased clinical crown height. However, recession type defects will not develop as long as the tooth is moved within the envelope of the alveolar process.

If the tooth movement is expected to result in the establishment of an alveolar bone dehiscence, the volume (thickness) of the covering soft tissue must be considered as a factor that may influence the development of soft tissue recessions during, as well as after, the phase of active orthodontic therapy. Orthodontic tooth movement per se will not cause soft tissue recession, but the thin gingiva that will be the consequence of the facial tooth movement may serve as a locus minorus resistentia to developing soft tissue defects in the presence of bacterial plaque and/or trauma caused by improper toothbrushing techniques. Before the orthodontic therapy is initiated, one should, therefore, carefully consider if the buccolingual thickness of the soft tissue on the pressure side of the tooth should be increased.

Hard tissue defects

Interproximal craters

These are two-wall defects, where the remaining walls are buccal and lingual walls. Attachment loss occurs on the mesial and distal surfaces of the adjacent roots. Orthodontic movement cannot improve interproximal craters.[7] It may be required to resort to respective bone removal and recontouring prior to orthodontic bracketing.

One-/two-wall bony defects

Such defects are treated more efficiently by Orthodontists. Ingber[8] recommends the technique of Orthodontic extrusion of teeth with infrabony pockets (with one- and two-wall bony pockets) that are difficult to treat by means of conventional periodontal therapy alone. In these situations, the orthodontist must place the bracket more apically on the facial surface of the crown and perpendicular to the long axis of the root of the tooth. As the tooth erupts, the orthodontist must equilibrate the crown to avoid premature contact with the teeth in the opposing arch, and increased mobility of the erupting tooth.[9] The extrusive tooth movement leads to a coronal positioning of intact connective tissue attachment and the bony defect is shallowed out. The orthodontically induced improvement of the crestal bone structure has been reported in clinical trails[810] and animal experiments.[11] The extrusive component is also the key factor in uprighting of tipped molars with a mesial angular bony lesion. In these situations, moving the tooth away from the osseous defect in a distoocclusal direction shallows out the slanted contour of the alveolar crest.[1213] Because of the tension of collagen fibers in the periodontal ligament, the alveolar bone follows the moving tooth on the mesial side, with the level of connective tissue attachment remaining unchanged.

Three-wall defects

These are not resolvable with orthodontics. If the patient cannot maintain a three-wall defect during orthodontic therapy, it must be resolved prior to bracket placement. These defects are generally treated with regenerative therapy, using either autogenous or alloplastic grafts in the affected region.

Furcation defects

Usually class 2 and class 3 furcation defects are typically not maintainable by patients during orthodontic therapy and decisions about their outcome must be made during the treatment planning process before beginning orthodontics. Their treatment most probably involves a regenerative approach, using membranes to isolate the defect to promote regeneration of the periodontal membrane, while the membrane blocks the ingrowth of the epithelium and would re-create the furcation defect.[7] If the tipped molars have furcation involvement before orthodontic uprighting, simultaneous extrusion may increase the severity of the furcation defects, especially in the presence of periodontal inflammation.[1415]

Horizontal bone loss

A common periodontal problem among adult orthodontic patients is generalized horizontal bone loss in the anterior region of the mouth. In these situations, if significant bone loss has occurred on all the anterior teeth, then often the teeth have disproportionate crown/root ratios. The orthodontist must recognize this problem prior to bracket placement. It may be appropriate in these situations to reduce the clinical crown lengths of these teeth to achieve improved crown/root ratio, hence reduced mobility.[16]