Dental Implants: Mastering Esthetics in the Smile Zone
Lee H. Silverstein, DDS, MS; Gregori M. Kurtzman, DDS; David Kurtzman, DDS; and Peter C. Shatz, DDS
The key to contemporary restorative dentistry is the fabrication of healthy, maintainable, esthetic, and functional prostheses. The true success of any restoration is reliant on the creation of an “illusion of reality,”1 regardless of the restorative modality used (eg, porcelain laminate veneers, crowns, and/or implant-supported prostheses).2 Developments and advances to the restorative armamentarium have significantly improved the clinician’s ability to deliver predictable and reliable treatments. Osseointegration is one of the essential components of implant therapy.3 It is universally accepted that implant dentistry is a restorative-driven treatment with a surgical component. 4
Mastering esthetics in the smile zone with the use of implant-supported restorations should involve:
- Proper diagnosis of smile design; gingival contours
- The existence of proper biologic width
- Proper decision making on site development
- Soft and hard tissue grafting to correct unesthetic or functionally compromised anatomic abnormalities
- The removal of excessive gingival and alveolar bone for the correction of “gummy” smiles.
All of these factors need to be considered during the treatment sequencing process and performed before placement of dental implants5 or the restoration of natural tooth-supported restorations.6-8
These aforementioned procedures are the blueprint to establishing a proper gingival smile line with correct biologic width. Crown lengthening is critical to the success of creating a smile that is harmoniously balanced with its surrounding facial features.9-12 Consequently, patients who clinically display too much gingiva and short teeth require a thorough diagnosis and treatment plan to provide a predictable esthetic outcome.13-15 This is especially imperative with the use of dental implant restorations according to these authors and advocated by Vincent Kokich, DDS.5 If a patient has altered passive eruption (APE) of the maxillary anterior teeth, either secondary to orthodontic treatment or without orthodontic therapy but with completed facial growth,16,17 then the surgeon must first correct the gingival levels with either a gingivectomy or esthetic crown-lengthening procedure before the placement of dental implants to ensure that the eventual gingival margins of the maxillary anterior teeth will be at their correct level relative to the adjacent anterior teeth, not only after restoration of the implant, but also over the long term.18
Biological width dictates that there be at least 3 mm between the most apical extension of the restorative margin and the alveolar bone crest.19 This allows sufficient room for the supracrestal collagen fibers that are part of the periodontal support mechanism, as well as providing a gingival crevice of 2 mm to 3 mm.20,21 If this guideline is followed, the restorative margin should be positioned approximately midway between the gingival tissue margin and the depth of the sulcus.22 Failure to allow sufficient space between the crown margin, be it on a natural tooth or an implant, and the alveolar crest height results in the finished restoration being positioned too deep in the periodontal tissues, which can result in increased inflammation and possible periodontal pocket formation.23
In a situation where no periodontal disease exists, the osseous structure roughly follows the scalloped parabolic contour of the cemento-enamel junction (CEJ), from facial to interproximal at an average distance of 2 mm to 3 mm.24,25 In addition, the average interproximal bone height is 3 mm coronal to the facial crest of bone (COB).26 Because the soft tissue topography is usually determined by the underlying hard tissue, this osseous “scallop” usually results in a gingival scallop of 3 mm.27 Examination of the periapical radiographs or periodontal vertical bite wings will allow the clinician to ascertain the position of the alveolar bone relative to the CEJ of the teeth28 to determine whether the COB is 2 mm to 3 mm apical to the CEJ, allowing for biologic width.29-31
However, in a clinical scenario where the COB is coronal to the CEJ, a condition results in APE.32-34 In this situation, the gingival margin will usually be located, on average, 3 mm coronal to the level of the COB, being more coronal on the body of the tooth and creating the appearance of a short clinical crown.35,36 These visual findings are coupled with the clinical information obtained by “bone sounding.” Bone sounding involves using a periodontal probe to locate the CEJ and determine whether it can be felt within the gingival sulcus or only when the probe penetrates through the base of the sulcus.37 Additionally, the periodontal probe is also used to feel for the COB. This value is expressed as a numerical distance in millimeters, revealing the distance between the COB and CEJ to ascertain whether there is sufficient biologic width.38Normally, the COB is 2 mm to 3 mm apical to the CEJ in a normal, non-diseased human periodontium.39
In addition to the gingival margin on the facial aspect of the teeth, in a non-diseased dentition the interproximal papilla between teeth with no bone loss due to periodontal disease is approximately 4.5 mm coronal to the interproximal COB. The mid-direct facial is about 1.5 mm more coronal to the COB. This additional 1.5 mm, with the 3-mm average osseous scallop from the CEJ, results in the tip of the papilla being an average of 4.5 mm coronal to the facial free gingival margin, where there is a “normal” periodontium, with no loss of bone or periodontal attachment due to periodontal disease.40
However, if the alveolar bone was situated in any other position other than normal, which is 2 mm to 3 mm apical from the CEJ, then these aforementioned values would not be the same and clinically relevant when used as a reference for the depth of a dental implant platform to allow for a proper emergence profile, according to the authors.
If implants are to replace missing teeth,then APE should be corrected before implant placement. In addition, if the patient has APE of the maxillary anterior segment, whether secondary to:
- orthodontic tooth movement;41
- a coronal gingival complex resulting from tissue hypertrophy secondary to plaque-induced inflammation;42
- medications such as calcium channel blocking agents, anticonvulsants, and immunosuppressant drugs;43
- deep decay causing short clinical crowns;44
- traumatic injury;44
- incisal attrition;45or
- tooth eruption and the patient has completed facial growth,46
The surgeon should first correct the aberrant gingival margins with an esthetic gingivectomy procedure, or the gingival margins and alveolar crest levels must be altered with an esthetic crown-lengthening procedure47 before the placement of the dental implant. These procedures can be accomplished at a separate surgical visit or at the time of dental implant placement but should be performed immediately before the preparation of the implant osteotomy, according to the authors and others.48,49 This will ensure that the eventual gingival margin over the dental implant will be at its correct level relative to the adjacent anterior teeth, according to the authors.
There are anatomic principles that act as parameters when practitioners perform esthetic gingival recontouring. A useful guide can be fabricated by the laboratory by modifying the mounted diagnostic casts so that the waxed modification reflects the ideal tooth anatomy desired in the final prosthesis, based on the guidelines previously published by Chiche and Pinault.50 These guidelines suggest that the average length for esthetically pleasing maxillary central incisors is 10 mm to 12 mm.51 These guidelines for the length of the central incisors, along with the recommended width-to-length ratio of 75% to 80%,52 should be kept in mind when recontouring the gingival tissues so as not to leave the teeth too long or too short.53
Once the central incisor proportions are achieved, practitioners should focus on the zenith or height of contour of the gingival margin on the centrals.54 The proper placement of the gingival zenith should be at the peak of the parabolic curvature of the gingival margin, which for the central incisors, cuspids, and bicuspids should specifically be located slightly distal to the middle of the long axis on these teeth. This gives the centrals, cuspids, and bicuspids the subtle distal root inclination that is paramount for the scaffold of a beautiful smile. The zenith for the lateral incisors is located at the midline of the long axis of the tooth. Furthermore, the height of the gingival crest for the lateral incisors should be 1 mm shorter than the gingival margins of the adjacent teeth. Additionally, the gingival tissues should be manipulated to have a resulting “knife-edge” gingival margin.55
Subsequent to the collection of the patient’s clinical data, which will reveal the presence of short clinical crowns and crestal bone levels approximating the CEJ, a diagnosis of APE can be made through the maxillary arch. The practitioner can then fabricate an esthetic guide that can be placed over the patient’s existing teeth to allow both the practitioner and patient to visualize what the smile will look like with the gingiva in a modified, more esthetic position.56
The repositioning of the gum line and crestal alveolar bone can be accomplished after the administration of local anesthetic. A periodontal probe is placed into the sulcus, attempting to locate the CEJ, but sometimes the CEJ cannot be discerned. In a case where the location of the CEJ is not clearly located, a periodontal probe should be passed through the periodontal attachment until the crest of alveolar bone is felt. Coupled with current periapical radiographs, the location of the crest of bone relative to the CEJ should be discernible.57
Periodontal, esthetic, and surgical crown-lengthening is then accomplished to correct the altered passive eruption. The laboratory-fabricated composite gingival esthetic guide can be used not only to position the alveolar crest 3 mm apical to the CEJ,58 but also to provide a blueprint for attaining horizontal gingival symmetry and height. The guide will also ensure proper interproximal scalloping based on the desired results. The newly established gingival margin will be determined by the patient’s lip line while smiling,59 the desired length of anterior teeth relative to the existing level of alveolar bone,60 and healthy interdental papillary tissue occupying the interdental spaces.61
Subsequent to scalloping the gingival tissues, an inverse beveled incision is made, connecting the sulci of the maxillary affected teeth. The surgical incision can transverse the base of the papillary tissue or it can follow the topography of the interdental papilla. For esthetic success at this critical phase of the crown-lengtheningprocess, it is important not to elevate the papilla, which usually will cause a loss of interproximal tissue height and may result in “black triangles.”
A full-thickness mucoperiosteal flap is then elevated with a periosteal elevator, and osseous resective techniques are performed with a surgical-length No. 8 round diamond bur and periodontal hand chisels to reshape the patient’s osseous bone margins. The surgical flap can then be positioned to the prearranged height determined by the esthetic surgical guide. The flaps are sutured using a 3/8 reverse cutting suture needle with a 4-0 thread size of polyglycolic acid (PGA), using a sling-suture technique. Suture removal is performed 10 days after surgery and the patient is instructed on the oral hygiene regimen to be used. This includes brushing with a soft-bristled toothbrush in a circular motion, and cleaning interdentally with either dental tape or floss.
After 10 weeks of postoperative healing, the cosmetic rehabilitation begins with the removal of the existing crowns. The teeth can be prepared with burs using the esthetic guide as the blueprint for tooth reduction. The restorations to be placed are ceramic crowns. These preparations are either placed at the free gingival margin or slightly subgingival on the facial aspect. Care should be taken not to violate the biologic width during the tooth preparation.62
Provisional restorations can be made by placing them in a vacuum-formed matrix made on the modified model, from which the esthetic surgical guide was fabricated, and then placed intraorally. After the appropriate time, approximately 60 to 90 seconds, the provisionals are removed and trimmed. The provisionals are bondedin place by spot-etching the preparations and using a luting material.
The occlusion should then be checked in the centric, protrusive, and lateral excursive positions63 and adjusted as needed. The patient should return to the office 10 days after insertion of the provisional restorations and provide input about what he/she likes and dislikes esthetically about the provisionals, and any changes that are desired. Subsequent to the recontouring of these provisional restorations to meet the patient’s expectations and gain the patient’s approval, impressions are taken and a putty matrix of the anterior segment is made to ensure the laboratory placed the incisal edges correctly.
Final impressions are obtained 6 to 8 weeks later64 by first placing a retraction cord, using a two-cord method with a woven cord, taking care not to injure the gingival tissues. Full-mouth impressions are taken with a vinyl polysiloxane facebow transfer, and open-bite centric relation records are obtained using registration material mounted in a semi-adjustable articulator. The case can be completed using full feldspathic porcelain crowns on teeth Nos. 6 through 11. Excess cement is removed with an explorer and periodontal scaler. The previously fabricated putty facial index should be placed to see if thereare any discrepancies, and any noted discrepancies should be modified.
The end result should be a healthy periodontal response and symmetry of the smile, which illustrates a completed healthy esthetic functional prosthetic result. The central incisors should demonstrate midline symmetry, as well as the correct 75% to 80% width-to-length ratio. In addition, the incisal smile line should follow the curvature of the lower lip. The newly established periodontal smile line should show a reduction of the gummy smile and make the smile more esthetically appealing and harmonious with surrounding facial features.65
Gingival levels should be assessed relative to the projected incisal edge position. The projected incisal edge position should be assessed relative to the position of the gingival levels. A predictable mode of determining the proper gingival positions is to determine the desired tooth size relative to the projected incisal edge position. The practitioner should remember that the incisal edge should not be positioned using the relative position of the gingival margin to create the proper tooth size. This is because the gingival margin can move with eruption or recession.66 Therefore, the proper gingival margin positions should be determined by establishing the correct width-to-length ratio of the maxillary anterior teeth.67 This can be accomplished by determining the desired amount of gingival display and creating symmetry between the teeth throughout the maxillary arch.68
In other words, if the existing position of the gingival margins creates the presence of a short clinical crown relative to the projected incisal edge position, then the gingival margins should be moved apically. This can be accomplished by performing esthetic crown lengthening, esthetic gingivectomy, orthodontic intrusion, and/or prosthetic rehabilitation.69 The procedure that is chosen to reposition the gum line is dependent upon several clinical factors, such as the location of the CEJ relative to the COB, the crown-to-root ratio and the shape of the root(s), the amountof existing tooth structure, and the sulcus/pocket depth. It is also paramount when establishing the proper position of the maxillary anterior teeth for an optimal cosmetic outcome to assess the levels of the interdental papillary tissues and their position relative to the crown length of the maxillary incisors.
One published article70 demonstrated that if the interdental contact is shorter than the interproximal papilla, then this could be an indication that there is clinically significant incisor abrasion. This scenario may cause shorter crowns, which shortens the contact between the central incisors. However, if the interdental contact point is longer than the papilla, then the gingival margin contour would be flat and usually located coronal to the CEJ, analogous to the clinical presentation of APE.71 The correction of this condition would be accomplished by performing esthetic crown lengthening72 and or orthodontic therapy to either extrude73 or intrude74the affected teeth.
Figure 1; Figure 2; Figure 3; Figure 4; Figure 5; Figure 6; Figure 7; Figure 8; and Figure 9 illustrate the concepts presented in this article. Patients who clinically display too much gingiva and short teeth require a thorough diagnosis and treatment plan to provide a predictable esthetic outcome. This is especially imperative with the use of implant restorations because, according to these authors, if a patient has APE of the maxillary anterior teeth, either secondary to orthodontic treatment or without orthodontic therapy but has completed facial growth, then the surgeon must first correct the gingival levels with either a gingivectomy or esthetic crown-lengthening procedure before the placement of dental implants. This will ensure that the eventual gingival margins of the maxillary anterior teeth will be at their correct level relative to the adjacent anterior teeth, not only after restoration of the implant, but also for a favorable long-term implant and/or natural tooth restoration.75It is essential that there be at least 3 mm between the most apical extension of the restorative margin and the alveolar bone crest. This allows sufficient room for the supracrestal collagen fibers that are part of the periodontal support mechanism, as well as providing a gingival crevice of 2 mm to 3 mm.
Essentially, the guideline of 3 mm on the facial from the COB to the gingival margin and 4 mm to 5 mm from the interproximal COB to the tip of the papilla for proper implant placement to allow for proper restorative contours would be irrelevant and erroneous if the periodontium and its hard and soft tissues were not located where they should be in a normal situation, with no bone and or attachment loss. Also, if the gingival marginis not located at the CEJ and the underlying bone is not 2 mm to 3 mm apical to the CEJ and after its parabolic contours, then the value of 3 mm on the facial and 4 mm to 5 mm on the interproximal area guideline for proper implant placement should not be used.
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About the Authors
Lee H. Silverstein, DDS, MS
Associate Clinical Professor of Periodontics
Medical College of Georgia
Gregori M. Kurtzman, DDS
Silver Spring, Maryland
David Kurtzman, DDS
General Private Practice
Hospital-Based Practice Treating Special
Peter C. Shatz, DDS
Assistant Clinical Professor of Periodontics
Medical College of Georgia