April 1, 2000
by Avishai Sadan, DMD, and Hisham Nasr, DDS
ABSTRACT: Correct esthetic proportions are the foundations for successful results; however, other factors, such as the extent of gingival display while one is smiling, are important as well. The article describes a simple, two-step approach for minimizing gingival display when the basic esthetic proportions are correct. The first step is surgical crown lengthening, the second shortening incisal edges. Emphasis is on sound biologic and mechanical principles.
One of the foundations of the pleasing esthetic smile is the extent of gingival display. Displaying the entire crown of the central incisor when one smiles is considered to be esthetically pleasing1 while excessive gingival display, the “gummy smile,” is considered to be esthetically unpleasing. Though the “gummy smile” may be the patient’s chief complaint, it is important to verify if this esthetic deficiency is an isolated problem or if other esthetic problems also exist.2 The following are common scenarios that are associated with excessive gingival display:
Young patients with short and wide teeth and excessive gingival display
The desired width-to-length ratio for central incisors is accepted to be 75-80%.1 Central incisors with values higher than 80% are considered to be short and wide. In young patients (mainly adolescents) the combination of short and wide teeth and excessive gingival display is usually due to altered passive eruption. The required treatment depends on the specific type of altered passive eruption and varies from gingivectomy to crown lengthening that involves resective osseous surgery.3 This treatment addresses both concerns since it improves the esthetic proportions and minimizes the extent of gingival display. Although loss of tooth structure due to parafunction and bruxism are uncommon in the adolescent patient, the clinician needs to rule them out as the cause for short and wide teeth.
Adults with short and wide teeth and excessive gingival display
Although adults may also present with altered passive eruption that was not diagnosed and addressed previously, other factors, such as parafunction and bruxism that can cause loss of tooth structure and subsequently short and wide teeth, may be present. In some instances, continuous eruption of the alveolar bone can completely compensate for the loss of tooth structure at the incisal edge. In such a scenario, no changes occur in the vertical dimension, and the end result is excessive display of gingival tissues of the erupted segment. Although crown lengthening may be required, it is likely that since root surfaces will be exposed prosthetic intervention, such as crowning or placing porcelain laminate veneers to restore the correct shape, may be needed as well.
Adults with short and wide teeth and no excessive gingival display
The previous scenario described an extreme end of the spectrum–the eruption completely compensating for the loss of tooth structure; the opposite, however, is also possible. Rapid loss of tooth structure (e.g., a bulimic bruxer) can by far exceed the natural ability of the alveolar bone to compensate for the loss of vertical dimension. In such a case, the patient will present only with short and wide teeth, and the required treatment is restoring the lost tooth structure and reestablishing the correct incisal edge position. This article will discuss in detail the significant factors involved in altering the incisal edge position.
The clinician must remember that although the aforementioned scenarios are possible, they represent the extreme ends of the spectrum, and in many instances the clinician will be presented with cases that fall between these extremes; thus, a combination of the suggested treatments may be required. Other factors, such as congenitally short and wide teeth, may also exist, but this article will focus on the last possible scenario: adults with correct proportions and excessive gingival display.
Adults with correct tooth proportions and excessive gingival display
When the tooth-to-tooth proportions4 and the width-to-length ratio1 are within the acceptable range and the chief complaint is excessive gingival display, a crown-lengthening procedure alone may adversely affect these proportions and create long and narrow teeth. In such a situation an additional step- shortening the incisal edge- is required. This will enable one to apically move the dentogingival complex and thus minimize the gingival display and maintain the original tooth dimensions. The technique mainly benefits patients who need restorations in the anterior teeth. Here are step-by-step guidelines for such a case.
DIAGNOSIS AND DATA COLLECTION
Figure 1 presents a patient with excessive gingival display and discolored teeth with failing extensive composite resin restorations throughout the maxillary anterior segment. The initial workout included radiographs, periodontal probing, preliminary impressions, and fabricating and mounting study casts in centric relation. The overall tooth-to-tooth proportions and width-to-length ratio of each tooth were within the esthetically pleasing range and will not be altered. The treatment plan was to apically move the dentogingival complex of teeth #s 4-13 without altering the teeth proportions. The incisal edges will be shortened after the surgical crown lengthening. Any alterations in the incisal edge position should be done while maintaining proper speech pattern, anterior guidance, incisal-edge display at rest, and proper incisal edge alignment.
Incisal-edge position and speech pattern: Correct production of the sounds f and v (e.g., forty-five, fifty-five) is an excellent guide for correct incisal edge position.5 Positioned correctly, the incisal edges of the maxillary anterior teeth should touch the wet-dry line on the lower lip during the production of these sounds.6 This is best evaluated when the patient is looking forward and the dentist is looking at his profile. If the incisal edges are currently touching this line, the ability to move the incisal edges buccolingually without adversely affecting the speech pattern may be limited. In the case under consideration, the incisal edges were properly positioned so the buccolingual alignment did not require any alterations.
Incisal-edge position and anterior guidance: The importance of proper anterior guidance for healthy occlusion cannot be overemphasized. While attempting to move the incisal edges apically, the clinician must retain the anterior guidance. Overshortening of the incisal edges may cause loss of overbite and resultant loss of anterior guidance. The first, easy-to-detect, adverse effect is no disclusion of the posterior teeth in excursions.7,8 Mount the study casts in centric relation to evaluate the feasibility of shortening incisal edges while maintaining adequate anterior guidance. Calibrate the condylar guidance with a protrusive overbite.9 The evaluation in the case under consideration indicated that up to 3.5 mm could be shortened from the maxillary anterior teeth while maintaining proper anterior guidance.
Incisal-edge display at rest: One of the factors of a youthful appearance is a display of at least 1-2 mm of incisal edge at rest.5 In order to evaluate the feasibility of shortening the incisal edges while still displaying the desired amount of incisal edges at rest, draw black on the areas to be removed to evaluate whether the remaining tooth structure will provide adequate display at rest. This resembles the technique utilized to evaluate and guide esthetic tooth contouring.10 In the case under consideration it was possible to shorten the teeth about 3 mm and still retain sufficient incisal-edge display at rest.
Incisal-edge position and incisal edge alignment: Of all the aforementioned, this is the most simple to control. The desired incisal-edge alignment should follow the curvature of the lower lip when one smiles.2,11
Communicating with the periodontal surgeon
The collected periodontal data in the case under consideration indicated that cervical
crown lengthening of 3 mm would not cause any adverse affects. Evaluation of the available amount of keratinized gingiva, root length, and the new expected crown-to-root ratio showed that this amount of lengthening would not compromise the periodontal health of the involved teeth. It is important to remember that the palatal bony plate would remain intact. If elective periodontal procedures are routine among the restorative-surgical team, these measurements should provide sufficient data for the surgical procedures. If the restorative-surgical team does not perform such procedures routinely, the use of a surgical stent may be beneficial. Use a high-speed handpiece to score the study cast at the cervical areas to the desired, new, free gingival levels. Once the cast is scored, a vacuum-formed template is fabricated, trimmed and transferred to the surgeon’s office. Figure 2 demonstrates the surgical stent intraorally.
Probe to bone to locate the exact position of the bony crest in relation to the gingival margins (Figure 3). This step provides information regarding the expected amount of bony resection.12 Figures 4-6 demonstrate the crown-lengthening procedure. In this instance, the soft tissue was scalloped following the stent guide, a full thickness flap was reflected, and the bony crest was resected on the buccal and interproximal aspects in order to establish the correct biologic width for the total estimated 3-4 mm13,14 of sound tooth structure coronally to the bone crest (Figure 6). The flap was repositioned and sutured, and a frenectomy procedure was also completed (Figures 7-8). The minimal suggested time for prior to subgingival placement of preparation’s margins is 3-4 months.15 During this time the teeth will appear long and narrow due to root-surface exposure, and black triangles may also be present.
Establishing new incisal edge position
Three to four months following surgery the periodontal condition is evaluated. The determining factor is a development of a 2-3 mm sulcus.15 The patient must be informed that an elective procedure of this nature is like any other plastic surgery procedure and reentries may be needed to refine the initial results. The same rules for healing periods apply for reentries. In the case under consideration, at 5 months postsurgery (Figure 9), it was decided that no reentries would be needed. The next stage is to establish the new incisal-edge position. Execute the process with a course disc on a straight handpiece attachment with the patient seated in an erect position facing the clinician. Complete the procedure on one side (Figure 10), and at each step evaluate centric relation and anterior guidance (Figure 11) as well as all of the other factors mentioned. After contouring one side, contour the opposing side. Evaluate centric relation and anterior guidance (Figure 12). At this point, the contoured teeth will serve as a verified guide for the length of the final restorations. Use an irreversible hydrocolloid impression of the upper arch to fabricate the temporary restorations at the verified length.
PREPARATIONS, TEMPORIZATION AND CEMENTATION
Since the finish line is placed on root surfaces, it is important to prepare the teeth with a parallel design to avoid pulpal exposure (Figure 13). Make the final impressions (Figure 14) and mount the master casts in centric relation (Figure 15). The final restorations in this case included 4 all-ceramic crowns on teeth #7-10, PFM with porcelain margins on teeth #4, 6, 11, 12, 13, (Figure 16), and a porcelain laminate veneer on tooth 5, which was the only tooth without preexisting extensive restorations. The all-ceramic restorations were bonded using resin cements, and the PFM were luted with resin-modified glass ionomer cement. Figures 17 and 18 present the teeth prior to preparation and cemented restorations at 2 months following delivery.
While other viable alternatives, such as orthognatic surgery combined with orthodontics and restorative procedures, can completely eliminate the excessive gingival display, the two-step technique described in this article provides the clinician with a practical method that can be implemented on a routine base.
The authors would like to acknowledge the assistance of Gerard Chiche, DDS, Chairperson, Department of Prosthodontics, LSU School of Dentistry, in the treatment of this case.
vishai Sadan is Assistant professor, Department of Prosthodontics, Louisiana State University School of Dentistry.
Hisham Nasr has a private practice limited to periodontics and implants, New Orleans, LA. Assistant clinical professor, departments of periodontics and prosthodontics, Louisiana State University School of Dentistry.
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