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In restorative dentistry and prosthodontics, clinicians oftentimes consider the "white esthetics" of the teeth in a case but overlook the "pink esthetics" of the gingiva. However, for an interdisciplinary restorative case to be truly successful, the gingiva must be appropriately positioned. Orthodontic tooth movement is one of the means by which the gingival position can be idealized. Other means to position the gingiva include crown lengthening, periodontal surgery, and adjustments to the emergence profile when restoration involves implant placement. An over-contoured facial emergence profile results in apical movement of the free gingival margin, and an under-contoured profile facilitates incisal positioning. However, there are limits to what this approach can achieve, which is why orthodontic treatment is a preferred strategy.
Gingival Zenith Position
The gingival zenith is the most apical extent of the free gingival margin of a particular tooth, and its position is an important consideration in treatment planning.1 Ideally, the gingival zeniths of a patient's maxillary teeth should be consonant with the upper lip; however, this can be challenging to achieve. The use of dermal fillers to enhance lip volume, as well as other factors, may alter the shape and morphology of the lip and make this goal even more challenging to achieve.
Although it is acceptable for the gingival zeniths of the maxillary central incisors, lateral incisors, and canines to be level with one another, the ideal positioning is for the gingival zeniths of the central incisors and the canines to be level with one another. The line connecting these zeniths is referred to as the "gingival line."2,3 In approximately 80% of patients, the gingival zenith of the maxillary lateral incisor falls incisal to the gingival line.4 The esthetics are considered to be ideal when the zeniths of the maxillary lateral incisors are approximately 1-mm incisal to the gingival line.5 The least esthetic scenario is for the zeniths of the maxillary lateral incisors to be apical to the gingival line. Furthermore, the gingival zeniths of the maxillary central incisors and canines should be slightly distal to their midlines whereas the zenith of the maxillary laterals should be centered on their midlines.5
Other considerations for achieving idealized gingival esthetics include gingival health, papilla morphology, and gingival display when smiling, and ultimately, the final restoration or prosthesis should be conducive to periodontal health. The gingiva should be stippled, pink, firm and matted. The papillae should be pointed, fill the gingival embrasures, and approximate the tooth proximal contacts.6 Failure to achieve appropriate papilla morphology may result in the development of open embrasure spaces or "black triangles." Although the extent to which gingival display is considered unsightly when a patient smiles and animates is subjective, typically, a gingival display of greater than 3 to 4 mm when animating is considered unesthetic.7
Altering the Gingival Zenith
There are a whole host of reasons why an individual may have an altered gingival zenith, including disease and inflammation, recession, dental crowding, or the positioning of the alveolar crest. Ultimately, the positioning of the gingival soft tissue will be determined by the positioning of the alveolar bone. The periodontium seeks to maintain the biologic width/supracrestal tissue attachment.8,9 Therefore, when the position of the alveolar crest is altered, the gingiva will follow. Vertical loss of the alveolar crest may result in apically positioned gingiva, whereas vertical advancement of the hard tissue will give way to incisally positioned gingiva. From this concept, the pithy saying that "the bone sets the tone" was born.
Ergo, if the positioning of the gingiva is unesthetic, it can be altered through several means. If recession is the problem, and the site is amenable to root coverage, an autologous connective tissue graft can be utilized. Soft-tissue grafting to address the gingival zenith is most appropriate when the zenith is apically positioned, but when it is incisally positioned, it may need to be altered with crown lengthening or orthodontics.10
When a tooth is orthodontically moved, the alveolar bone often follows the tooth. Movement of a tooth that results in movement of the surrounding bone ultimately alters the gingival position. However, it should be noted that if the tooth is moved beyond the alveolar housing, a fenestration or dehiscence may result. Therefore, orthodontic tooth movement requires careful planning and caution.
When the incisal edge of a maxillary tooth is observed to be in infraocclsion with the adjacent dentition, it is often indicative of tooth ankylosis. This is an important consideration when the use of orthodontics is being contemplated to alter a gingival zenith position. The term ankylosis is broadly defined as the union of two separate fixtures. When a tooth becomes ankylosed, the cementum of the root is fused to the alveolar bone.11 If a tooth is ankylosed in a growing child, it will not continue to move vertically with the subsequent growth of the alveolar process. Radiographically, ankylosis presents as an interruption in the periodontal membrane space. It has also been reported that ankylosed teeth elicit a "metallic" sound upon percussion. However, ankylosed teeth often have some sort of restoration because the ankylosis occurred as a result of trauma, and the presence of a restoration can make it difficult to delineate whether or not a metallic sound is the result of ankylosis or the restoration.
An ankylosed tooth can be treated through distraction osteogenesis.12 This is, however, a complex, advanced procedure. Distraction osteogenesis is a technique in which the bone surrounding the ankylosed tooth is surgically separated from the adjacent bone and then orthodontic brackets and wires act as a distraction device.13 The gradual separation of the bone that occurs during distraction osteogenesis results in the genesis of new bone.
It is this author's opinion that orthodontic tooth movement is an underutilized strategy in comprehensive treatment planning and that this can largely be attributed to the fact that clinicians are not always exposed to orthodontics during their training. It is challenging for dental schools to include an advanced education in orthodontics as a part of their undergraduate curricula because there is already immense pressure to satisfy a myriad of other requirements. Postgraduate residencies are also challenged by time constraints and may therefore exclude orthodontic treatment planning due to the extensive time commitment required to complete a case involving orthodontics. Nonetheless, orthodontics should be considered as an integral component of comprehensive treatment planning.
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About the Author
Melissa Seibert, DMD, MS
Creator and Host
Dental Digest Podcast
US Air Force Dentist
Langley Air Force Base
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