The Periodontal Crown: Creating Healthy Tissue

Increasing attention is being given by our patients to their physical health. With increasing life expectancy they have a great desire to live their remaining years feeling well, maintaining a good appearance, and a healthy smile.

ORAL-SYSTEMIC HEALTH: A BRIEF BACKGROUND
Coronary heart disease (CHD) is the leading cause of death and morbidity in the United States and many developed countries. Nearly 500,000 people in 2002 died from CHD and millions of others are living with it.1 It is estimated that, in the United States in 2006, heart disease cost more than 258 billion dollars in health-related costs and lost productivity, affecting more than 80 million adults, with 38.2 million estimated to be less than 60 years of age.2
Recently, chronic inflammation has been implicated etiologically in CHD and cardiovascular disease.3 Periodontal disease, a form of chronic inflammation, affects tooth-supported structures, with an estimated prevalence of as high as 75% of adults in the United States.4 The disease is now associated with elevations of blood markers which signify chronic in­flammation.5 Because of the evidence implicating chronic inflammation in the etiology of CHD, and possible etiologic relationship be­tween periodontal disease and CHD, every dental treatment procedure should be directed toward addressing and reducing inflammation.
Since many of these patients identified with cardiac risk want to maintain or improve their smile, cosmetic dental materials, which have antibacterial, anti-inflammatory properties, must be utilized. Full crowns with antibacterial subgingival margins should be the preference for this category of patients. This article will focus upon this topic of discussion.

Figure 1. Poorly fitted subgingival margins on teeth Nos. 6 and 11, resulting in an inflamed, darkened cervical tissue color, compromising the appearance of the restoration. Figure 2. Captek crowns, replacing poorly fitted PFM restorations in Figure 1, exhibiting optimal gingival margins and crown contours, producing a highly aesthetic appearance.

PERIODONTAL EFFECTS OF RESTORATIVE MATERIALS AND MARGIN PLACEMENT
Unfortunately, dental restorations have been considered a major contributory factor in the etiology of periodontal disease, as discussed by Loe6 in his classic 1968 paper. His paper reviewed the reactions of the periodontal tissues to restorative procedures, and the effect of these restorative materials on the periodontal tissue. He believed and stated that any known type of dental restoration that extends into the subgingival area causes damage to the periodontal tissue, either by providing possibilities for bacterial retention, and/or by a direct irritation effect from the material. In the author’s opinion, if the connection between periodontal disease/ inflammation and cardiac disease is a valid one, then these procedures must either be avoided wherever possible or, they should be done using a periodontal-friendly material that reduces the bacterial load (contamination).
Because of the possible harm to the periodontal tissue, it has been suggested that margins of full crowns, when done, be placed coronal to the gingival margin.7 However, Austin et al,8 suggested such a placement is often contraindicated due to aesthetic requirements, subgingival caries, existing subgingival restorations, or a short clinical crown. With the patient’s primary concern being aesthetics, it is obvious that most margin placements must now be subgingival.
Subgingival margins are of great concern because of the potential problems that can occur (Figure 1). Waerhaug9 suggested that the subgingival margin facilitates bacterial plaque retention, which could later contribute to the destruction of the periodontal supporting apparatus. Silness,10 20 years following Waerhaug, in 1980, described subgingival margins to exhibit more severe gingival lesions and deeper gingival pockets than margins even-with or above the gingival crest. Con­sidering the possible connection between periodontal and cardiac disease, these effects of cosmetic treatment must be avoided at all costs to reduce the risk of systemic disease occurring from oral conditions.
Amsterdam11 wrote a classic treatise on periodontal prostheses, more than 30 years ago, establishing the standard of care for a crown. Most critically, he described the optimal margin/finish line. When full-coverage restorations were indicated, this margin/finish line should be placed (in a healthy sulcus) at minimal depth, just short of the junctional epithelium; or completely away from the sulcus, preferably on the anatomic crown. He suggested that the least desirable location to place a margin is just supragingival, where the area of greatest plaque accumulation occurs. Finally, in guidelines still followed today, he suggested that to prevent plaque build­up it is necessary to create optimal crown contours with proper coronal form, embrasure form, and good subgingival fit at the margin (Figure 2).
Despite this excellent treatise, one which defined the standard of care for the placement of full crowns, Morman, et al12 reported that gingival inflammation could result from the placement of gold inlays, even with perfectly adapted and well-polished margins. With the most precise techniques utilized to avoid adverse effects―including proper preparation, impressions, well-fitted provisionals, and definitive crown restorations,―there could still be gingival irritation and increased plaque retentions.

RESTORATIVE MATERIALS VERSUS INFLAMMATION

Figure 3. Goodsen, et al13 clinical study results comparing surface material of tooth versus amount of bacteria present in sulcus.

Following the standard of care established by Amsterdam,11 all dentists should consider using materials that will maintain good periodontal health with optimal fit, reducing possible periodontal risks for systemic disease. When the need exists to employ full-coverage crowns, Captek (Precious Chemicals) provides one example of a cosmetic restorative crown material available that can help satisfy the goal of excellent health. This ceramo­metal crown incorporates the use of a gold composite metal coping. Good­son, et al13 (Figure 3) documented a reduction of up to 91% in the number of bacteria observed surrounding Captek restored teeth versus normal tooth surfaces in the same mouth. Additionally, there was approximately 96% less bacterial adhesion compared to ceramic-fused-to-noble-metal restorations.
Chronic inflammation in the periodontal tissue has been traditionally reduced with nonsurgical periodontal care, involving scaling, root planing, and effective oral hygiene to remove the bacteria plaque responsible for the problem. It has always been under­stood, following the suggestions of Amsterdam,11 that proper placement would help to prevent plaque buildup, in effect reducing inflammation. With significantly positive tissue responses to crown materials, dentists can now achieve predictable aesthetic restor­ations with a healthy supporting periodontium. These crowns might best be described as “periodontal crowns,” since healthy tissue results from placement on any affected teeth. In the author’s opinion, this type of crown management should be followed, if there is even the smallest possibility of reducing periodontal risk for cardiac disease with placement of these crowns.

COMPOSITE GOLD ALLOY MATERIAL DESCRIPTION AND PROPERTIES
The Captek composite gold alloy coping is fabricated using a capillary casting technique. It is not a traditional gold alloy, but is best described as a composite metal―of 97% gold reinforced with small particles of a very high-fusing, high-strength, platinum/palladium core.14 The resulting warm hue presents an ideal background for natural/vital porcelain aesthetics in the cervical areas of restorations, virtually eliminating tissue shadowing often caused by the gray color of traditional cast ceramometal alloys. The material does not oxidize, which can create dark color reactions with porcelain, creating a weak link at the bonding surface. Captek has a small particle size under 15 to 20 µm, allowing margins to be finished to a fine edge without a loss of integrity. With no oxides15 or gray metal to mask out, only 0.05 mm is required for a proper opaque layer compared with an average of 0.3 mm on cast metal.
Because of the bacterial inhibition properties, the author prefers a chamfer bevel with a prescribed small metal collar used in all nonaesthetic areas, generally from midproximal (Figure 4).13,16-18 These margin designs also work well with bridges that in the past restricted pontic length to 15 mm. However, an all new Captek material, Bridge & Implant, has been reinforced with twice the number of platinum/palladium particles, making it more than 30% stronger than original Captek.19 Developed using nano technology and in use for over 2 years, this stronger Captek can be used for cantilever and long-span bridges offering at least the same level of fit and plaque inhibition as the original Captek.19

Figure 4. Captek metal anywhere along the margin will inhibit bacterial plaque adhesion. Figure 5. Illustration of how the high gold infiltrates capillary structure of reinforcing platinum/palladium core.

TYPICAL CLINICAL CASE EXAMPLE
This example patient case shows a concern about tissue health, aesthetics, strength, and fit.
A 45-year-old female presented with congenitally missing teeth maxillary lateral incisors; teeth Nos. 7 and 10. Previously she had had dual-cantilever bridges made to replace these teeth. After consultation, it was decided to complete two, 3-unit bridges for teeth Nos. 6 to 8 and 9 to 11. When the old crowns were removed on the upper left side, the inflammation of the tissue where the previous fitted semiprecious metal crowns were in place was obvious. With the bilateral placement of “periodontal crowns” (using Captek composite metal in this case), the improved fit and tissue health is easily vis­ible―even 4 years after placement (Figure 1).

CONCLUDING REMARKS: SHOULD THE STANDARD OF CARE CHANGE?
While Dr. Amsterdam11 established the initial standard of care for crown design and margin placement, clinical studies and case histories now dictate an amendment of this classic standard. Whenever any full-crown restoration is considered or required for a tooth (with bleeding in the tissue when probed or where periodontal disease is present) it is now suggested, based on the knowledge of crown contour and possible reduction of tissue inflammation, that using periodontally healthy crowns is an appropriate indication. Because the crowns (Captek) discussed in this article have been shown to be one ex­ample of a material that reduces plaque on the associated tooth (per the studies of Goodsen, et al13 cited previously), perhaps the term “periodontal crown” is a very appropriate one to use.
In the author’s opinion, restoring a tooth with a material that has been shown to reduce the inherent risk of additional plaque retention should be considered the treatment of choice. Use of these crowns, in the presence of periodontal disease, should be routine. Should this be a future standard of care? The hope is that more attention will be given to study materials that can provide the periodontal benefits of a hybrid gold. When considering the possibility that risk of cardiac disease and adult onset diabetes might be reduced with periodontal crown treatment, the future is exciting!

References

1. Kochanek KD, Murphy SL, Anderson RN, et al. Deaths: final data for 2002. Natl Vital Stat Rep. 2004;53:1-115.
2. Thom T, Haase N, Rosamond W, et al. Heart disease and stroke statistics—2006 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. 2006; 113:e85-151.
3. Ridker PM, Hennekens CH, Buring JE, et al. C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women. N Engl J Med. 2000;342: 836-843.
4. Brown LJ, Brunelle JA, Kingman A. Periodontal status in the United States, 1988-1991: prevalence, extent, and demographic variation. J Dent Res. 1996;75:672-683.
5. Noack B, Genco RJ, Trevisan M, et al. Periodontal infections contribute to elevated systemic C-reactive protein level. J Periodontol. 2001;72:1221-1227.
6. Loe H. Reactions of marginal periodontal tissues to restorative procedures. Int Dent J. 1968;18:759-778.
7. Richter WA, Ueno H. Relationship of crown margin placement to gingival inflammation. J Prosthet Dent. 1973;30:156-161.
8. Austin GB, Vogel R, Deasy M, et al. Effect of rough and smooth margins on interproximal gingival health. Clin Prev Dent. 1979;1:19-26.
9. Waerhaug J. Histologic considerations which govern where the margins of restorations should be located in relation to the gingiva. Dent Clin North Am. 1960;5:161-176.
10. Silness J. Fixed prosthodontics and periodontal health. Dent Clin North Am. 1980;24:317-329.
11. Amsterdam M. Periodontal prosthesis: Twenty-five years in retrospect. Alpha Omegan. 1974;67:8-52.
12. Mormann W, Regolati B, Renggli HH. Gingival reaction to well-fitted subgingival proximal gold inlays. J Clin Periodontol. 1974;1:120-125.
13. Goodson JM, Shoher I, Imber S, et al. Reduced dental plaque accumulation on composite gold alloy margins. J Periodontal Res. 2001;36:252-259.
14. McLaren E. Forward to the past: a renaissance in ceramometal technology. Contemp Esthet Restor Pract. 1998;2(spec issue):6-13.
15. Zappala C, Shoher I, Battaini P. Microstructural aspects of the Captek alloy for porcelain-fused-to-metal restorations. J Esthet Dent. 1996; 8:151-156.
16. Shoher I, Whiteman A. Captek: a new capillary casting technology for ceramometal restorations. Quintes­sence Dent Tech. 1995; 18:9-20
17. Knorr S, Combe EC, Wolff LS, Hodges JS. The Surface Free Energy of Gold Alloy Systems. Abstract presented at: 32nd Annual Meeting of the American Association for Dental Research; March 2003; San Antonio.
18. Wynne WPD. Margin Design in the Most Overlooked Aesthetic Zone. Dentistry Today. October 2006;25:126-129.
19. DiTolla M. From the Lab. Dental Economics. 2007;97:44.

Dr. Gottehrer has been in practice in suburban Philadelphia for more than 30 years, focusing his practice on cosmetics, implant dentistry, and periodontics. He is a graduate of the University of Maryland Dental School, received his postgraduate periodontal training at the University of Pennsylvania, and is a board certified Periodontist. He teaches the Senior Elective Course in Periodontics at the University of Maryland Dental School. He has been published and lectures internationally. Dr. Gottehrer is currently the president of the Institute of Advanced Oral and Physical Health in Havertown, Pa. He can be reached at (610) 449-9500 or dr.neilg@verizon.net.

Disclosure: Dr. Gottehrer reports no conflict of interest.