RSM as a standalone therapy has, rightly or wrongly, been accused of overuse.
Establishing the goals of the completed treatment (in terms of esthetics, perio-dontal health, occlusion and long-term stability) must guide the decision making process as to whether conventional orthodontics is the most appropriate treat-ment, and what limitations there might be on treatment outcomes if orthodon-tics is not employed.
The Need for Restoration
If there is a restoration that needs to be replaced, poor tooth size, shape or pro-portion, or tooth colour problems, then orthodontics will have to provide some other significant advantage to the case outcome in order to justify its use as the primary course of treatment. On the other hand, if the teeth do not require restorative treatment other than bleaching or selective recontouring then there are compelling reasons for conventional orthodontics and leaving the teeth uncut and unrestored.4
As good as our current techniques and materials are, there is no evidence that even the most perfect of restorations will survive a lifetime. In fact, nothing gets
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close. The most successful dental restoration is the gold crown with 50% sur-vival of around 17 years. Everything else has a shorter sursur-vival span and while a crown may survive, the underlying tooth could fail. Patients are sometimes not made aware of the truth about restoration failure and without the facts they often opt for ceramic veneers, but once given the data 2 out of 3 (in a study of 146 patients each with 10 veneers) opted for a noninvasive therapy. This is especially relevant when dealing with young individuals as the expediency of the quick fix must be weighed against the long-term consequences of preparing teeth that would not otherwise require restoration.
Teeth that will remain inherently unattractive after orthodontic treatment is completed will challenge the treatment planning process to determine whether an acceptable result can be achieved by restoration alone, or whether it is neces-sary to use both orthodontics and restorative dentistry to create the desired esthetic outcome.4
Restorative treatment options for correcting spatially compromised cases include esthetic contouring, bonding, porcelain laminates and crowns. The underlying condition of the dentition is a factor in determining which restorative option is best. Teeth without any restorations or caries should be treated as conservatively as possible. If only minor modifications to tooth contours are required to achieve the desired esthetic result then contouring and bonding provides the least inva-sive treatment. Caries in the teeth to be treated may require that more exteninva-sive restorations be considered, such as porcelain laminates or crowns. The size and location of the caries may dictate the design of these restorations.5
Occlusal stability:
1. Regardless of the esthetics achieved, whether through orthodontics, RSM or a combination of both, the occlusion must be stable.6
2. Varying occlusal patterns can be found in spatially compromised dentitions and treatment of a malocclusion can present a challenge due to the
associated spatial discrepancies. In order to achieve a more predictable esthetic and functional result, an occlusal analysis should be included in the treatment planning process and the best option, orthodontics, restorative dentistry or a combination of both modalities, clearly
identified.7 While restorative dentistry can often solve the esthetic problems of anterior teeth, it frequently cannot correct occlusal relationships.
The pretreatment occlusion as compared to the anticipated post-treatment occlusion must be considered. The goal is to create a stable physiological occlu-sion that can exist healthily regardless of the pre-existing maloccluocclu-sion.2 Minor to moderate discrepancies in tooth position and alignment are generally
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receptive to RSM and slight to moderate disharmony in rotation and tipping are also considered practical candidates. However, moderate to severe intra-arch discrepancies are not appropriate for RSM, and treatment of severe discrepan-cies of the facial and dentofacial midlines and bodily displaced or transposed teeth is contraindicated due to the limited esthetic improvement that can be achieved when compared to the need for extensive dental mutilation.2
Periodontal Architecture
The appearance of the teeth and gums must act in concert to provide a balanced and harmonious smile. A defect in the surrounding pink tissue cannot be com-pensated by the quality of the dental restoration and vice versa.8 In the past decade, there has been a remarkable upswing in interdisciplinary collaboration among dentist, orthodontist and periodontist in smile enhancement.9 Chapter 5 covers pink esthetics in more detail.
As a rule, variations in gingival margin height are due to differences in bone level or sulcus depth between teeth in the same patient;4 however, it is possible that the bone levels vary not because of bony recession but because of differ-ences in tooth eruption. An example would be two overlapped central incisors, one to the lingual and one to the facial aspect. The tooth to the lingual aspect will always exhibit more wear than the one to the facial aspect. As it wears, it will erupt, bringing the bone in a coronal direction and resulting in a coronally placed gingival margin (Fig. 6.3).4
Fig. 6.3 Lingually positioned tooth number 9 presents a more coronal gingival margin when compared to buccally positioned tooth number 8.
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Another possible cause of aberrations in gingival margin height is variation in sulcus depth between the central incisors, despite correct bone levels. The tooth with the shallower sulcus will have a more apically positioned gingival margin than the one with a deeper sulcus. This variation in sulcus depth is common in cases of anterior tooth malposition. The more labially inclined teeth have a thinner gingiva and a shallow sulcus. The more lingually placed teeth have a thicker gingiva and a deeper sulcus (Fig. 6.3).4
Periodontal surgery can alter gingival margins and it is much easier to remove soft tissue or bone than to create it. If the most apical free gingival margin level is determined to be appropriate, it is possible to use either gingivectomy or osseous surgery to apically position the gingival margin heights of the other teeth to this position. However, if this process would create excessively long and thin-appearing teeth, then a new problem has been created. Although connec-tive tissue grafting is predictable and effecconnec-tive for covering exposed root surfaces, it is far less predictable for moving tissue coronally to cover enamel or ceramic on labially positioned teeth. Therefore, in cases that have a high smile line and the most apically positioned free gingival margin is unacceptable, orthodontics to reposition the teeth and tissue is the most predictable solution.4 Coronally positioned gingival margins and deep sulci, which are the result of lingually positioned teeth, can be corrected by tooth repositioning. The gingiva will thin to a normal thickness and sulcus depth will move to a normal level. Similarly, a tooth in labial version with slightly apical thin tissue and a shallow sulcus can be correctly positioned causing the gingiva to thicken and the sulcus to assume a normal depth.
Laser or electrosurgery can be used to sculpt the free gingival margins to ideal levels during cosmetic restorative procedures. The modifications can result in a far more pleasing esthetic effect. However, the practitioner must identify the cause of the gingival aberration prior to selecting the mode of treatment for the gingival levels. If the problem is one of bony levels, then either osseous flap surgery or transmucosal laser recontouring is necessary to provide biological health and tissue stability. It is biologically acceptable to correct by sculpting an excessive sulcus depth that exists due to a lingually positioned tooth. Unfortu-nately a significant amount of tissue regrowth may occur since the tooth is in lingual version. Orthodontic repositioning of the tooth can also alleviate this problem.4
The papilla levels are at least as critical to the overall esthetics of anterior teeth as are the levels of the free gingival margins. Papillae that are positioned too far apically result in either an open gingival embrasure (black triangle) or the devel-opment of an excessively long contact and rectangular looking teeth. This is a risk associated with enamel stripping that is common in aligner treatments. See
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Chapter 7 for discussion on aligner therapies. Three factors come into play in establishing papilla levels: underlying bone level; the patient’s biological width;
and the gingival embrasure and contact area. The patient’s biological width is relatively constant, and bone level, embrasure form and contact area can vary dramatically with tooth eruption. A significant esthetic challenge for the restor-ative dentist is created by this variance. In general, unless a patient has had wear or excessive overjet and secondary eruption, the interproximal bone is rarely positioned too far coronally. Additionally, unless the patient has had periodontal disease, the interproximal bone is rarely positioned too far apically. Thus, in most patients who present for cosmetic procedures, variations in papilla level are related to embrasure form and contact area. Interestingly, excessively large embrasures, as in diastemata, can result in papillae that are positioned apically.
Excessively small embrasures, as in overlapped or rotated teeth, can also result in papillae that are positioned apically.4 If the most apically positioned papilla would result in the need for an excessively long contact area and unpleasing coronal form, then, in order to achieve a truly esthetic result, orthodontics is the only solution. Currently there are few reliable periodontal procedures that can increase the height of interproximal bone and none that can predictably grow interproximal soft tissue. However, overlapped teeth can be aligned, inter-proximal bone and soft tissue moved coronally, and the entirety of the esthetic result of diastemata closure can be enhanced with orthodontic treatment.4 Dentogingival Structural Compromises
Restorative correction of a malalignment frequently requires aggressive tooth preparation. Near amputation of the existing coronal form is often required of a labially positioned tooth to bring it into line. To avoid an excessively thick incisal edge, a lingually positioned tooth needs significant lingual tooth prepara-tion. Rotated teeth may require a combination of significant labial and lingual reduction on mesial and distal aspects to accomplish the desired alignment. It is an interesting challenge to determine how much tooth preparation is accept-able in a treatment plan. There are no clear-cut guidelines indicating that a particular degree of reduction will result in a successful result. Nevertheless, it does seem prudent to consider the patient’s age and current dental condition when determining appropriate reduction.4 As the pulpal chamber size decreases with age, this parameter is influenced by the individual characteristics of each case and the age of the patient.1
The parameters for RSM are defined by the dimensions and structures of the teeth and the surrounding periodontium within the dental arches. There are limits to the amount of tooth structure that can be removed before pulpal and periodontal violation results. Excessive tooth removal to accomplish the goals