Written by G. Thomas Phillips, DDS Friday, 01 July 2005 00:00
We as dental clinicians are accustomed to altering bone to eliminate periodontal osseous defects or to provide a sufficient ferrule for a restoratively compromised tooth. However, based on my 27 years of clinical observation, altering osseous contours to improve aesthetic restorative results is an underutilized procedure. This article will discuss the procedures for establishing aesthetic clinical crown lengths and proportions and how to alter osseous architecture to arrive accurately at the desired results.
The patient is a 30-year-old database/program administrator. She was referred by another patient and came seeking cosmetic improvements. Initial examination included a full-mouth series of radiographs, study casts, and photos. Following collection of all the necessary data, the patient was scheduled for a consultation.
|Figures 1 and 2. Preoperative close-up.|
|Figure 3. Preoperative full-face view.||Figure 4. Mounted preoperative models.|
The patient had congenitally missing maxillary lateral incisors and retained primary maxillary canines (Figures 1 and 2). Teeth Nos. 6 and 11 occupied the lateral incisor positions. It was observed in the full-face photos (Figure 3) that the patient had a normal lip line when smiling, but had excessive gingival display in the area of the premolars and primary canines. In the ideal aesthetic display we wish to see the upper lip at or near the free gingival margin and no dark buccal corridors when the patient displays a full smile. Further observation revealed that the central incisors were a little too long. This was demonstrated by having the patient say and hold the e sound with the teeth in maximum intercuspation. Ideally, the central incisors should fill 50% to 70% of the space between the upper and lower lip. Filling less than 50% allows the clinician to lengthen the teeth incisally if desired. If the central incisors fill greater than 70%, then it is advisable not to lengthen the teeth incisally. The mounted casts of the dentition (Figure 4) revealed that the patient had a class I posterior occlusion and minimal attrition. Examination revealed no TMJ dysfunction and no abnormal tooth mobility. Examination of the dentition was unremarkable except for a stainless steel crown on tooth No. 19, which was placed when the patient was a teenager.
There was slight wear of the central incisors because of a restricted envelope of function. This was confirmed by measuring from the middle of the incisive papillae to the facials of teeth Nos. 8 and 9; the measurement was 7.9 mm. A more shallow guidance would be built into these 2 teeth, bringing the measurement into the ideal 9.0 mm range. This would also enhance the aesthetics.
Based on our present state of the science, orthodontics would ideally be initiated to move teeth Nos. 6 and 11 into proper position, following extraction of teeth C and H, creating a space for implant placement for teeth Nos. 7 and 10. However, the patient flatly refused this treatment when it was proposed at the initial consultation. She absolutely would not agree to orthodontic treatment. With this decision, the patient was scheduled for a second consultation to allow me time to assess and propose possible alternative treatments. At the second consultation appointment, the following alternative was proposed:
(1) a total crown and bridge approach to correct the problems,
(2) osseous recontouring to achieve a more idealized gingival tooth display,
(3) extraction of teeth C and H and development of ovate pontic form, and
(4) endodontic therapy for tooth No. 6 to allow sufficient tooth alteration to mimic a lateral incisor.
|FIgure 5. Dimension chart. Dimension chart.|
When making aesthetic dimensional changes to teeth, this practitioner works out the final dimensions mathematically (Figure 5). We know from dental anatomy the average lengths and widths of teeth that result in an ideal ratio of length to width.1 The lengths and widths of all teeth to be altered were measured and their corresponding ratios recorded. The existing recorded dimensions were compared to ideal dimen-sions, working with dimensional alterations to approach the ideal ratios as closely as possible. In Figure 5, note the column marked “changes.” These are the final changes to existing lengths and widths to achieve the desired dimensions. A knowledgeable laboratory technician can also create the illusion of perceived lengths and/or widths by controlling crown contours.
The laboratory doing the wax-up (DB’s Dental Laboratory) was sent a copy of the dimension chart, the preoperative casts, and prescription. The laboratory was instructed to wax crowns at the recorded dimensions along with instructions in the “notes” block at the bottom of the chart.
Following receipt of the wax-up, an appointment was scheduled for patient review and approval. Following approval, the wax-up was sent to the provisional laboratory (Resista Temps, Indianapolis, Ind). The laboratory was instructed to fabricate ovate pontics for teeth Nos. 6 and 11 and follow the wax-up precisely in building the provisional restorations.
Regarding osseous changes following extractions and the anatomy of the periodontium, we know from the studies of Gargiulo2 and Ingber, Maynard, and Nevins,3-5 the average measurements and anatomy of the periodontium. Vacek6 re-vealed the variability of biologic width (the combination of the junctional epithelium and connective tissue attachment). The reader is urged to review this important article concerning this variability. For simplicity, this author is dealing with average dimensions of biologic width. Review of Figure 6a shows the normal dimensions and anatomy of the periodontium. From the free gingival margin to the junctional epithelium, the measurement is 0.69 mm. The junctional epithelium, a loosely bound attachment via hemidesmasones, is 0.97 mm; from the bottom of the junctional epithelium to the crest of the bone is the tightly bound connective tissue attachment, which is 1.07 mm. These measurements are of academic interest, since we cannot clinically measure a 0.69-mm sulcus. Clinically relevant measurements are approximately 0.5 mm to 0.7 mm, 1.0 mm, and 1.1 mm, respectively. These anatomical components from the free gingival margin to the crest of the bone constitute the dentogingival complex, which clinically is close to 3.0 mm on the facial aspect.
|Figure 6a. Dentogingival complex.||Figure 6b. Illustration of crestal heights.|
Kois7,8 has demonstrated that the above-referenced 3.0-mm dimension constitutes the normal crest (Figure 6b). Clinically, this dimension is measured under local anesthesia by sounding with a flat-ended periodontal probe (Neph-ron Dental Supply) from the free gingival margin to the crest of the bone. Eighty-five percent of the time one will encounter a normal crest situation on the facial surface, 2% of the time a high crest anatomy (< 3.0 mm), and 13% of the time a low crest anatomy (> 3.0 mm).
This has clinical relevance in predicting outcomes of crown margin locations and gingival health. If there is a high crest facial anatomy and the margin is an intrasulcular margin, then there will be a violation of the biologic width. This will result in chronic gingival inflammation. Alternatively, if dealing with a low crest anatomy and soft tissue is abusively manipulated in the preparation or impression technique, then recession will occur. The amount of recession usually equals the difference between the low crest gingival measurement and 3.0 mm. Interproximally, the normal measurement will be approximately 4.5 mm. This discussion has referenced the facial only. Readers are urged to review the referenced literature.
In order to achieve a good aesthetic result with the extraction site, there must be a review of what is known about post-extraction osseous behavior. Referencing Kois,9 with a normal periodontium there will be 2 mm of apical osseous recession following a tooth extraction in the anterior segment. It makes no difference whether immediate grafts are done in the extraction site. An immediate extraction site graft will maintain buccal-lingual ossesous dimension so that there is no collapsed ridge. Knowing there will be 2 mm of apical migration allows us to plan cosmetically for this occurrence.
Lastly, development of ovate pontic form should be discussed. Ovate pontic development at the time of extraction is achieved by building an ovate form onto the pontic 3 mm into the extraction site. Post-healing, this will allow for the previously mentioned 2-mm apical osseous migration and a 1-mm soft-tissue indentation for an emergence profile. Ovate pontics offer many advantages and no disadvantages: they support papillae (no black holes), help
to preserve buccal-lingual ridge dimension, provide for pontics that are indistinguishable from natural teeth since they appear to emerge from the gingiva, and are the most cleansable, easily maintained pontics. Once a clinician masters ovate pontics, this procedure will replace all other pontic forms.
Armed with a chart of precise, desired tooth measurements, laboratory provisional crowns evolved from a wax-up, and knowledge of the periodontal architecture, extraction site dynamics, and ovate pontic form, the patient was scheduled for the initial appointment.
The patient had previous endodontic therapy performed on tooth No. 6 by an endodontist. Following anesthesia, the first task was to establish the clinical lengths of pontics Nos. 6 and 11. Looking at the column indicating changes and new lengths (Figure 5), it is observed that tooth No. 6 is to be lengthened gingivally by 2.7 mm and tooth No. 11 by 1.5 mm. Using electrosurgery, soft tissue was removed to obtain the lengths as measured from the incisial tips of teeth C and H. This becomes the free gingival margin for the ovate pontics. Osseous crown lengthening procedures were performed next. A full-thickness horizontal flap was made from the distal of tooth No. 3 to the distal of tooth No. 14. This was a horizontal flap—not a scalloped flap. This was done to minimally disturb and interrupt the blood supply to the papillae. This helps avoid destruction of the papillae and possible ensuing black triangles. Following reflection of the flap, teeth Nos. 8 and 9 were shortened by 1 mm (Figure 5).
With the following procedure for cosmetic osseous contouring one can predictably obtain desired crown lengths to within approximately 0.2 mm or less. Using digital caliphers throughout the procedure, take the desired crown length and add 3 mm. Why 3 mm? Referring back to the dimensions and anatomy of the periodontium, we know that the dimension from the free gingival margin to the crest of the bone is 3 mm for a normal crest anatomy. As an example, referring to teeth Nos. 8 and 9 in the chart, the desired clinical crown length is 10.5 mm. The calipers were set for 13.5 mm. From the incisal edge, facial bone was removed until the 13.5 mm measurement was reached. Osseous resection was performed using a sterile, round carbide bur at low RPM in a turbine handpiece and an Ochsenbein surgical chisel. The bone was removed on the facial of the root from the distal to mesial line angles of each tooth, blending it with the interproximal bone. This procedure was repeated tooth by tooth until osseous recontouring was completed.
(Note: These guidelines are appropriate for doing full-coverage crowns or veneers. If crown extension is being performed with no plans for any restorations, the technique would be modified. In such a case the bone would be moved apically no more than 2 mm from the CEJ to prevent root exposure. The 3.0-mm dimension starts 1 mm incisally from the CEJ and ends 2 mm apical to the CEJ. In such a case you would sacrifice ideal crown length in favor of avoiding intentional root exposure. Intentional root exposure would be an aesthetic compromise and cause possible root sensitivity.
It should also be noted that developing ovate pontic form for primary teeth that have resorbed roots requires a different protocol than ovate pontic development for teeth with normal root structure.)
Soft tissue was removed until the proper clinical pontic lengths were obtained. The flap was temporarily repositioned. From the free gingival margin a measurement of 3 mm apically was made, and the bone was marked at this level. Using a round bur, a 3-mm root form concavity was shaped into the bone. When the ovate portion of the pontic is formed, it will be placed 1 mm into the concavity. The remaining 2 mm will allow the granulation of soft tissue over the bone. Since there are no roots, do not expect to have the normal 2 mm of apical resorption nor the buccal-lingual collapse of tissue. The exact pontic site has been surgically created, negating the need for any bone grafts. Upon completion of the osseous recontouring, interrupted silk sutures were used to secure the soft-tissue flap.
The teeth were now prepared to the present gingival line, which was 3 mm coronal to the osseous level. Lingually and interproximally the teeth were prepared to the free gingival line. The prefabricated provisionals were now lined with Jet acrylic (Lang), trimmed to the margins, contoured, occlusion adjusted, and polished using standard provisional crown techniques. The pontics were customized into ovate pontics as follows:
The apical area was abraded using an air abrader. The surface was coated with an unfilled resin and light-cured. Holding the provisional bridge upside down, a flowable composite layer was added to the apical area and cured. Holding it upside down allows gravity to form the composite into an ovate or rounded form. The bridge was seated. Using a Sharpie pen, a line was marked on the pontic at the free gingival level. The bridge was removed, and a measurement of 1 mm apically from this line was made. The excess was removed, and an ovate pontic shape was made. If dealing with a normal extraction, then the ovate pontic would be placed 3 mm into the extraction site (see previous discussion). There was now a pontic form that would heal with a 1-mm tissue indention and allow for 2 mm of soft tissue to granulate between the bone and the pontic.
The bridges and crowns were cemented in place with provisional cement. The patient was given appropriate postoperative instructions for extractions and periodontal surgery, and instructions for what to do and not to do with the ovate pontic sites (avoid passing floss over the apical area of the pontic for 3 months).
The patient was seen a week later for observation and suture removal. Over the next 3 months she was appointed for brief observations. The 3-month time period allows for osseous and gingival maturation. The patient was appointed for final impressions 3 months after the initial preparation. The provisionals were removed and teeth re-prepared to the existing gingival margins. Prior to removing the provisionals, the length of each tooth was measured to confirm the dimensions initially calculated. In every case the measurements were within 0.2 mm (as measured from the incisal edge to the free gingival margin) of the desired lengths.
|Figure 7. Polyether crown and bridge impressions.||Figure 8. Prepared teeth and ovate tissue form prior to impressions.|
|Figures 9 and 10. Laboratory model of preparations and crown margins.|
The tissue was prepared for final impressions using electrosurgery. I do not use retraction cord for crown and bridge. If nothing else is learned from this article, please consider learning to use electrosurgery for crown and bridge. Disregard all of the myths, and they are myths, about the tissue and nerve damage caused by using electrosurgery. Electrosurgery produces more predictable, better, and more consistent impressions for the vast majority of dentists. I have been using it for crown and bridge impressions exclusively for 18 years. Figures 7 to 10 show the impression, the preparations, and the uncut stone model. You can see that every margin is well-defined 360º around each tooth. This was done with the first impression. I refer you to the bibliography for an in-depth discussion of this excellent and invaluable technique.10-12 The literature supports this treatment modality. There is a learning curve to master the technique, but it is well worth the effort. The impression material used was a polyether.
Figures 8 and 10 show the ovate pontic form that was developed over 3 months. Note the preservation of the papillae. Some will note redness of the tissue in the pontic site. This is not inflammation. It is the body’s attempt to establish a junctional epithelial attachment to the pontic. Crucial to employing the ovate pontic is having a laboratory that understands ovate pontic form and how to develop it.
|Figure 11. Provisional crowns 3 months following preparation.|
Following repreparation of the teeth and the final impressions, the provisionals were relined and recontoured as necessary. A face bow was made using the Kois analyzer (Panadent). This face bow is highly recommended. Opposing alginate impressions and maximum intercuspation occlusal records were made. Following recementation of the provisional crown, an impression was made of the provisionals. This cast was sent to the laboratory with instructions to use it as a guide for fabricating the final restorations. Figure 11 shows the provisional crowns.
The following items were sent to the laboratory:
(1) the final impressions,
(2) opposing stone model,
(3) maximum intercuspation occlusal records,
(4) model of the provisional crowns,
(5) a series of color slides to include a full-face photo to allow the ceramist to relate to the patient—this gives the ceramist the artistic license to characterize the teeth appropriately for the patient’s facial features, age, and gender; slides with shade tabs for the desired shade,
(6) preoperative models to allow the laboratory to understand where I started and where I want to go,
(7) a copy of my measurement chart,
(8) a detailed prescription of what I want,
(9) the wax-up model, and
(10) face bow.
|Figure 12. Laboratory wax-up.||Figure 13. Completed porcelain crowns on solid stone model.|
In the proper sequence of treatment a wax model is made from the dimensional analysis and detailed laboratory instructions. Laboratory provisional crowns are evolved from the wax-up. The laboratory builds the porcelain from the models of the provisionals. Figures 12 and 13 show the comparison of the wax-up and final porcelain-to-metal restorations.
|Figures 14. Postoperative close-up.||Figure 15. Postoperative full-face view.|
The porcelain artistry was performed by Gary Nunokawa at LeBeau Dental Laboratory in Kent, Wash. The case was received in our office approximately 2 months after submission to the laboratory. The patient was scheduled for seating and delivery of the restorations. The crown and bridge restorations were seated and checked for contours, aesthetics, occlusion, marginal fit, and contacts. Radiographs were taken to confirm interproximal marginal fit. Note the following in Figure 14 about the final restorations: the new lengths compared to the original teeth, gingival contours, the illusion created of making the permanent maxillary canines mimic lateral incisors with proper proportioning, and the ovate pontics. Note the preservation of the papillae at the pontic sites and how the ovate pontics appear to be natural teeth emerging from the gingiva. Figure 15 shows a full-face view. The patient was demonstrably ecstatic with the final result. Following patient approval, the crowns were cemented with a resin-modified glass ionomer cement.
Quoting from the patient’s much appreciated 1-page letter to me, (following the initial provisionalization appointment) she said, “My life changed from that moment in a dramatic way.”
A detailed discussion of how a cosmetic dentition can be achieved by altering and controlling osseous architecture has been presented.
1. Wheeler RC. A Textbook of Dental Anatomy and Physiology. 4th ed. Philadelphia, Pa: Saunders; 1965:125-199.
2. Gargiulo AW, Wentz FM, Orban B. Dimensions and relations of the dentogingival junction in humans. J Periodontol. 1961;32:261-267.
3. Ingber JS, Rose LF, Coslet JG. The “biologic width” – a concept in periodontics and restorative dentistry. Alpha Omegan. 1977;70:62-65.
4. Maynard JG Jr, Wilson RD. Physiologic dimensions of the periodontium significant to the restorative dentist. J Periodontol. 1979;50:170-174.
5. Nevins M, Skurow HM. The intracrevicular restorative margin, the biologic width, and the maintenance of the gingival margin. Int J Periodontics Restorative Dent. 1984;4:30-49.
6. Vacek JS, Gher ME, Assad DA, et al. The dimensions of the human dentogingival junction. Int J Periodontics Restorative Dent. 1994;14:154-165.
7. Kois JC. Altering gingival levels: the restorative connection, part I: biological variables. J Esthet Dent. 1994;6:3-9.
8. Kois JC. The restorative-periodontal interface: biological parameters. Periodontol 2000. 1996;11:29-38.
9. Kois JC. Esthetic extraction site development: the biologic variables. Contemp Esthet Restorative Pract. 1998;2:10-17.
10. Phillips GT. Electrosurgery for crown and bridge. Dent Today. 1997;16:98-103.
11. McCrannahan WW. Soft tissue care for GPs. GP Insider. 1991;3.
12. Sherman JA. A low cost, effective alternative technique to laser surgery. GP Insider. 1992;9:129-132.
Dr. Phillips maintains a cosmetic, crown and bridge, and implant practice in Fredericksburg, Va. He is a graduate of the Medical College of Virginia School of Dentistry and holds a degree in industrial engineering from Pennsylvania State University. He has been a guest lecturer at the Medical College of Virginia, Case Western Reserve University School of Dentistry in Cleveland, Ohio, and numerous regional study clubs, and has done 1-day courses for hygienists on crown and bridge and cosmetic dentistry. Dr. Phillips is a mentor with Creating Restorative Excellence, founded by Dr. John Kois. He can be reached at (540) 371-6700.
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