Soft Tissue Management
With Metal-Ceramic and
All-Ceramic Crown Systems

Many advances have been made in recent years to the science and the art of metal-ceramic and all-ceramic restorations. However, no matter how natural and lifelike such restorations may be, the final esthetic result is most dependent upon the health and level of the surrounding gingival tissues. The key to success is effective soft tissue management, and the goal of this soft tissue management has been to provide healthy gingival tissues covering sound, smooth restorative margins.

Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.

Figure 1. Tooth Nos. 7, 9 and 10 have been restored with metal-ceramic crowns, with the exception of a porcelain labial margin on No. 7. The crowns on teeth Nos. 9 and 10 have many esthetic deficiencies, and recession of the gingival tissues has exposed the unsightly metal gingival margins. Figure 2. The obvious chronic marginal inflammation displayed around the crown on tooth No. 9 is typical of biologic width violation.

The past three decades have witnessed numerous improvements in metal-ceramic and all-ceramic crowns. In spite of these technological improvements, the majority of esthetic failures with such restorations are biologic. The two primary types of esthetic failure have been recession of the gingival tissues resulting in exposure of the restorative margins and the presence of chronic marginal gingival inflammation (Figures 1 and 2).

Figure 3. Teeth Nos. 5 and 29 have metal-ceramic restorations with supragingival margins and a metal collar. Such margins provide excellent marginal integrity and can be used where esthetics is not critical. Figure 4. The porcelain laminate veneer on tooth No. 10 has a supragingival margin that is almost invisible because of the contact lens effect that occurs with these restorations.

When metal-ceramic crowns were introduced to the profession in the late 1950s, shoulder-bevel margins with metal collars were advocated to provide optimal fit (Figure 3). ¹ To obtain acceptable esthetics, the metal margins were intended to be hidden within the confines of the gingival sulcus. This concept proved to be rather unpredictable and lead to the development of numerous techniques for fabrication of all-porcelain labial margins with metal-ceramic crowns. ^2-7 The evolution of such simplified techniques, along with the introduction of several innovative all-ceramic crown modalities, has eliminated the necessity of hiding metal margins deep in the gingival sulcus. However, it is clear that it is impossible to precisely match the shade of the restoration with the color of the gingival portion of the tooth with these restorations, and in most clinical situations it is still desirable to hide the restorative margins underneath the healthy gingival tissues. The exception to this statement is bonded porcelain veneers, where tooth reduction is minimal and the restoration is bonded to sound enamel. In these situations, the contact lens effect allows margins to be placed in a supragingival location (Figure 4).

Gingival Recession

Gingival recession in adults is not a natural effect of aging but rather is a result of pathology. If excellent gingival health is attained prior to definitive margin placement and proper clinical techniques are utilized, the relationship between the prepared restorative margin and the gingival tissues can be very stable, as long as the patient practices proper oral hygiene. There are a number of ways to prevent gingival recession related to anterior crown fabrication, but most of these are under control of the clinician.

Figure 5. The anterior teeth have been prepared with supragingival margins and provisional restorations fabricated prior to and during definitive periodontal therapy

One of the most important factors in the predictability of the final result is ensuring that the gingival tissues are very healthy at the time of definitive margin placement and making of the impression. Most often patients requiring extensive restoration of anterior teeth do not present with healthy gingival tissues. ⁸ Preparing these teeth for esthetic crown restorations and making the impressions at the same appointment in the presence of gingival inflammation or periodontal disease is a prescription for disaster.

Figure 6. The provisional restorations on teeth Nos. 22 through 27 demonstrate excellentesthetics, marginal integrity and physiologic crown contour. Figure 7A. The patient presented with a poorly contoured provisional restoration on tooth No. 8. Figure 7B. The tooth preparation was completed. Figure 7C. A new provisional restoration was fabricated and designed to contour the gingival tissues.

With placement of the definitive restorations a few weeks later, it is reasonable to assume an improved effort on behalf of the patient to comply with oral hygiene procedures, and often in these situations the inflammation in the gingival tissues will resolve or at least be reduced. In these situations, the gingival tissues will move in an apical direction, often exposing the restorative margins. This can occur during the provisional phase or shortly after the definitive restorations are placed. In either situation, the clinician is faced with an esthetic failure.

The optimum approach is to wait to determine the final margin location when the gingival tissues have attained a state of optimal health. With most anterior restorations, the approach recommended is to prepare the teeth, leaving the margins in a slightly supragingival location (Figure 5). Excellent provisional restorations are fabricated, which restore optimum crown and gingival tissue contours, provide access for proper oral hygiene, and serve as predictors for the definitive restorations (Figures 6 and 7 A through C). ⁹ Whatever periodontal procedures are necessary to return the tissues to a state of optimal health are performed. After the tissues are deemed healthy with accepted clinical parameters, the patient is placed on Peridex (Colgate/Palmolive, Cincinnati, Ohio) for two weeks. ¹⁰ The optimal location for the gingival margin is determined, and the margin is prepared. Impressions are made and the patient continues rinsing with Peridex until the definitive restorations are placed.

It is essential that tooth preparation does not result in damage to the gingival tissues. Pre-packing the gingival sulcus with retraction cord prior to placing the margin in the confines of the sulcus will prevent iatrogenic damage. On removal of the cord, a defined space permits dropping of the margin with minimal chance for trauma. Use of rotary instruments especially designed to minimize trauma is recommended (Tissue Protection Diamonds, Premier Dental Products, Norristown, Pa. ) (Figure 8).

Figure 8. Tissue protection diamonds, such as these illustrated here (Premier Dental Products, Norristown, Pa.) are excellent for atraumatically dropping cervical margins to a subgingival location.

It is also critical not to damage the attachment apparatus during gingival displacement procedures. The philosophy of attaining optimum gingival health prior to definitive margin location, coupled with placement of the gingival margin a short distance into the gingival sulcus, permits relatively atraumatic retraction procedures. A suitable diameter retraction cord (Ultrapack Retraction Cord, Ultradent Products, Salt Lake City, Utah) soaked in a hemostatic agent (Hemodent, Premier Dental Products, Norristown, Pa.) is placed in the gingival sulcus for eight to 10 minutes. ¹¹ Prior to removal of the cord, it is soaked with water to prevent damage to the inner epithelial lining of the sulcus. ¹²

The importance of fabricating quality provisional restorations cannot be overemphasized. These restorations may be made early in the restorative sequence as part of the healing phase or after the preparations are finalized. In either event, such provisionals must demonstrate physiologic crown contours and excellent marginal integrity and provide adequate esthetics. The authors prefer an indirect/direct technique for provisional fabrication, but whatever technique is utilized, the aforementioned parameters must be met. ^13-15

When final cementation is with a conventional dental luting agent, such as zinc phosphate or glass ionomer cement, a zinc oxide-eugenol temporary cement (Temp-Bond, Kerr Dental Mfg., Romulus, Mich.) is preferred. While it is now known that zinc oxide-eugenol cements are not obtundent to pulpal tissues, they do provide an excellent initial seal of the prepared tooth. This tends to eliminate sensitivity during the provisional stage. However, zinc oxide-eugenol is a potent soft tissue irritant, and care must be taken that all excess temporary luting agent is removed from the sulcus prior to dismissing the patient. Any residual cement left in the sulcus will result in significant inflammation. This inflammation is transitory and will resolve with cementation of the definitive restorations; but when the tissue heals, it will be at a more apical level and the resultant recession may expose the restorative margins.

When patients require periodontal surgical procedures such as crown lengthening, sufficient time must be allowed after the surgery to permit stabilization of the gingival crest. It is often stated that a waiting period of six to eight weeks is required to attain adequate stability. However, for many patients, this time frame is far too short. ¹⁶ In a majority of patients, a waiting period of five to six months is recommended. This will mean that many patients will be wearing provisional restorations for protracted lengths of time. It is recommended that such provisional restorations be removed and recemented approximately every six weeks to prevent leakage and subsequent recurrent caries.

In summary, recession in association with the placement of anterior restorations is preventable. Attaining optimum soft tissue health prior to final determination of margin location is essential. Atraumatic tooth preparation and gingival displacement procedures are required, along with the fabrication of excellent provisional restorations. A meticulous technique for provisional cementation is critical, and provision must be made for tissue shrinkage after periodontal surgical procedures.

Gingival Inflammation

Figure 9. The inflammation around the crowns on teeth Nos. 10 and 11 is typical of biologic width violation and is not likely simply a result of poor oral hygiene.

While recession exposing the gingival margins has been a primary cause of esthetic failure with metal-ceramic and all-ceramic restorations, an equally compelling problem is the chronic marginal inflammation in the gingival tissues associated with such restorations (Figure 9). For many years, such marginal inflammation was attributed to poor oral hygiene, and the patient was admonished to improve oral physiotherapy, usually to no avail.

Figure 10. The metal-ceramic splinted fixed partial denture on these anterior teeth have all-porcelain labial margins (except tooth No. 7, ovate pontic) that are smooth and esthetic, and provide adequate marginal integrity. Figure 11. Metal-ceramic crowns (teeth Nos. 8, 9 and 10) with a properly placed porcelain labial margin can provide excellent esthetics and periodontal health.

Certain cervical marginal configurations have been demonstrated to be inherently rough and thus to increase the potential for plaque accumulation and retention. Therefore, they may contribute significantly to such marginal inflammation. ¹⁷ It is clear that smooth margins of highly polished metal or glazed porcelain are the optimum materials to be placed in the gingival sulcus (Figures 10 and 11).

However, possibly a majority of chronic inflammatory gingival responses are likely caused by a violation of biologic width. ^18,19 It is tempting for the clinician, especially when having experienced recession in previous patients, to decide to place crown margins deep into the gingival sulcus to prevent marginal exposure in the event of recession. Clinical studies have demonstrated that the closer the restorative margin is to the attachment, the poorer is the periodontal response, or expressed another way, the further the margin is from the attachment, the better is the periodontal response. ²⁰ Specific recommendations have been made to place the restorative margins 0.5 mm from the healthy free gingival margin, or more precisely, a minimum of 3.0 mm from the alveolar crest. ^21,22

Figure 12. These restorations have been placed deep in the sulcus, and the resultant violation of biologic width has caused the chronic gingival inflammation. Figure 13. After the crowns in Figure 12 have been removed, it is obvious how deep into the sulcus the margins were placed. Crown lengthening is necessary to move the gingival attachment to a more apical position.

It is the opinion of the authors that the etiology of the gingival inflammation seen in the majority of anterior crown restorations is biologic width violation because margins are routinely placed too deep into the sulcus (Figures 12 and 13). Often, this results from the clinician not following the anatomical sculpting of the gingival tissues, and the interproximal margins are place too close to the attachment.

While almost all authorities recommend supragingival crown margin placement wherever possible, most anterior crowns are automatically prepared with subgingival margins for esthetic reasons. One excellent study demonstrated that as many as 25 percent of patients do not display the anterior gingival tissues with a normal or even and exaggerated smile. ²³ This finding has significant clinical implications in that if patient consent is obtained, many anterior restorations can be placed with supragingival margins, which results in an improved periodontal response, better evaluation of marginal integrity, and substantially simplified operative procedures. ²⁴

In summary, chronic marginal inflammation associated with anterior crowns can be prevented by using restorative margins that are inherently smooth and by placement of such margins a relatively short distance (0.5 mm) into the sulcus as measured from the crest of healthy gingival tissues. Margins must be a minimum of 3 mm from the alveolar crest, and patients must be instructed in and encouraged to perform optimum oral hygiene procedures.

Summary and Conclusions

Many advances have been made in recent years to the science and the art of metal-ceramic and all-ceramic restorations. However, no matter how natural and lifelike such restorations may be, the final esthetic result is most dependent upon the health and level of the surrounding gingival tissues. The key to success is effective soft tissue management, and the goal of this soft tissue management has been to provide healthy gingival tissues covering sound, smooth restorative margins. The essential details for effective soft tissue management have been delineated and expanded upon, and are the same whether all-ceramic or metal-ceramic restorations are utilized. Successful, meticulous attention to detail will result in clinical success regardless of the type of restoration chosen.


Authors

Terry E. Donovan, DDS, is an associate professor and executive associate dean at the University of Southern California School of Dentistry. He is also chairman of the Department of Restorative Dentistry and co-director for advanced education in prosthodontics.

George C. Cho, DDS, is an assistant professor and the director of clinical education for Advanced Education in Prosthodontics at the USC School of Dentistry.

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To request a printed copy of this article, please contact Terry E. Donovan, DDS, USC School of Dentistry, DEN 4368, MC 0641, Los Angeles, CA 90089-0641.