April 1, 2001
by Thomas Trinkner, DDS, and Paul Steigerwald, DDS
The development of modern dental ceramics has resulted in a restoration that demonstrates superior cosmetic results due to enhanced color and translucency, greater functional stability and strength, and which promotes soft tissue compatibility (Figs. 1 & 2). Further, these restorations enable dentists to conservatively yet predictably complete preparation designs. According largely to anecdotal reports, these combined benefits have also contributed to an overall improvement in patients’ oral health and hygiene habits, (Figs. 3 & 4) in addition to contributing to a holistic approach to health and well-being that recognizes patient lifestyle and self-esteem as significant to treatment outcomes. These interrelated results have led to widespread success for dentists when placing all-ceramic restorations.
Although anecdotal testimonials regarding the biologic benefits of all-ceramic restorations may be beyond reproach, it is imperative that controlled long-term in-vivo research definitely demonstrate the manner in which the placement of this material in the mouth can benefit the soft tissues and contribute to overall improvements in the oral environment. The biocompatibility of the material has been repeatedly noted throughout the literature. What is lacking, however, is a sound reservoir of research that confirms the benefits of using all-ceramic restorations for specific clinical situations, particularly as compared to other restorative modalities, as well as to conditions that involve only natural dentition. (Figs. 5-9)
The area of gingival health that is of particular interest, and the protocol associated with placing all-ceramic restorations that contribute to a positive soft tissue response include margin placement and restoration formation. Combined with the inherent properties and characteristics of the material, such protocol have been observed to result in reduced plaque accumulation and increased overall gingival and oral health.
GINGIVAL BENEFITS OF ALL-CERAMIC RESTORATIONS
The aesthetic appearance and health of the gingiva are influenced by several factors, including the natural dentition or materials used to replace lost tooth structure. The tooth structure in the gingival third demonstrates a normal color and value, light transmission and fluorescence and a form that supports the gingiva. Therefore, it behooves clinicians to select restorative material that mimics such natural optical characteristics, supports the gingiva, and exhibits a non-pitted, smooth and highly polished surface that can contribute to reduced plaque formation.1 (Figs. 10 & 11.)
Clinicians have repeatedly noted enhanced tissue response and improved soft tissue esthetics following the placement of all-ceramic restorations. Due to the almost natural wear characteristics demonstrated by all-ceramic restorations, occlusal stability can be more predictably maintained, thereby reducing detrimental cervical changes that result from parafunctional conditions. A pink, stippled surface free of inflammation–which is characteristic of healthy gingival tissue–contributes to patient satisfaction with the treatment outcome, improved self-esteem, and commitment to maintaining proper oral hygiene activities following treatment. (Figs. 12 & 13.)
REDUCED PLAQUE FORMATION RESULTING FROM SURFACE CHARACTERISTICS
The singular factor which influences gingival and overall oral health is the amount of plaque that accumulates on the restorative material and/or the natural tooth. To this end, researchers have conducted numerous studies to determine the optimum material for use in restorations, and all-ceramic materials consistently achieve greater oral health through a reduction in plaque accumulation. (Figs. 14 & 15.)
In recent years, studies have focused on the effects of specific all-ceramic materials on gingival health. In particular, a retrospective in-vivo evaluation examined the occurrence of plaque and certain gingival conditions following placement and long-term function of all-ceramic restorations and found that the majority of the all-ceramic crowns (IPS Empress) rated excellent for margin integrity after more than 3 years. Additionally, with regard to plaque accumulation and bleeding on probing, no significant differences were found between the all-ceramic crowns and the controls.2 (Figs. 16-18)
Despite the lack of studies regarding all-ceramic full-coverage crowns placed by general practitioners, these same researchers evaluated the clinical performance of other brands of all-ceramic restorations (Dicor). In such studies, the researchers again found that there was no more plaque or bleeding on probing in connection with the all-ceramic crowns than in the control surfaces.3
However, there have been other studies conducted to access whether the placement of all-ceramic restorations improves gingival health and helps to reduce the levels of plaque and bacteria present in the gingiva. In one study that evaluated the response of microbial plaque and gingival inflammation to the placement of porcelain laminate veneers, the researchers found that, compared to a baseline, there were statistically significant reductions in the plaque index and plaque bacteria vitality following placement of the veneers.4 Such findings should serve as motivation for the initiation of additional clinical research to assess the long-term benefits of placing all-ceramic restorations regarding reduced plaque formation. (Figs. 19 & 20.)
Given that some researchers have observed a reduced plaque formation surrounding the placement of all-ceramic restorations, studies have been conducted to more closely identify the characteristics of this restorative material which, in particular, contribute to such a clinically beneficial condition within the oral environment. To this end, it has been demonstrated that very smooth surfaces harbor sparse deposits of plaque, while rougher surfaces, such as amalgam, can be covered by more plaque,5 suggesting that surface roughness contributes to plaque accumulation.
Further, comparative studies have found that all-ceramic crowns have little soft debris retention compared to other materials, such as cast gold or acrylic resin veneer crowns, which demonstrated increased plaque retention.6 These results also indicated that ceramics are easily cleaned and exhibit low plaque retention, and that increasing the area of ceramic surfaces on restorations decreases plaque retention,6 thereby contributing to enhanced overall oral health.
Still other studies have found that a rough restoration surface attracts and retains bacterial plaque and irritates surrounding soft tissues.7 Other researchers have reported that the surface roughness value and the amount of plaque adhesion decreased with an increase in the polishing level of porcelain restorations.8
EFFECT OF MARGIN PLACEMENT AND INTEGRITY ON GINGIVAL HEALTH
The most problematic area for clinicians to restore is the gingival one third of the tooth, which is crucial to creating an aesthetic and harmonious appearance between the restoration and the soft tissue. Therefore, to achieve an indiscernible margin for the restoration, dentists have followed specific processes and protocol to optimize biologic and aesthetic results.1 (Figs. 21 & 22.)
Such procedures have involved, but are not limited to, placing the margin within the gingival sulcus, placing materials that mimic natural tooth structure and/or more greatly promote gingival health, and creating a restorative form that supports the gingival tissue.1 Also of significance during any restorative process is respecting the biologic width, since restorative margins that violate the biologic width usually result in poor gingival response.9,10,11
After all, it has been noted that, no matter how natural and lifelike the all-ceramic restorations may be, overall oral health is dependent upon the health of the surrounding gingival tissues, which is positively affected by sound, smooth restorative margins.12 (Figs. 23-25)
EFFECT OF RESTORATION SHAPE ON GINGIVAL HEALTH
Too often restorations are undercontoured, creating a straight or negative emergence profile that does not adequately support the gingival tissue. However, there are times when the restoration form may be overcontoured, which leaves little room for the papilla.1 The shape of restorations is particularly significant when they are supported by implant systems, a clinical situation in which the contour and emergence profile of the restorations promotes easy access for maintenance of proper oral hygiene.13 (Figs. 26-29) Specifically, all-ceramic restorations enable the creation of embrasures and emergence profiles that are more plaque free as a result of the more natural dimensions that can be achieved when using this material.
For years practitioners were torn when it came to creating an esthetic restoration that was compatible with the periodontal supportive structures. Meeting patient expectations for movie-star teeth often required decisions that led to a treatment that did not follow the periodontal prescription for health. Once gums are distressed, so is the bone. (Figs. 30-33) Once this occurs, the entire restoration or esthetic effect can be lost. When patients develop swollen, inflamed gingiva that shrink back as a result of a procedure presented to them as “cosmetic,” the level of potential dissatisfaction becomes obvious.
Therefore, successful cosmetic dentistry requires the preservation of a healthy periodontium.12,14 If the proper relationship between restorative demands and periodontal supportive tissues does not exist, then procedures to create the proper environment must be performed.16,19 Further, it is important for dentists to realize that soft tissue damage can occur at any stage of treatment: during preparation, provisionalization, or final seating.19,20 (Figs. 34-37.) Throughout the years, metal-ceramic restorations have demonstrated and required procedures and protocol which have compromised gingival health, such as traumatic retraction techniques, sub-gingival marginal placement, and excessive contouring, all of which affect the intrinsic relationship between the periodontium and the restoration.12,14-18 (Figs. 38 & 39.) Conversely, the use of all-ceramic restorations has come of age from the standpoint of biocompatibility with the periodontal tissues and achieving the expected esthetic outcome.12,14,17
With this in mind, it becomes clear that what was first presented in the early 1990s as a possibility for all-ceramic restorations is definitely achievable when certain clinical protocol are followed. Such results can include all-ceramic restorations which are biologically compatible, enable careful subgingival depth placement, promote proper subgingival and supragingival contours, and contribute to marginal integrity and a polished bonding surface.14
Advances in all-ceramic materials and in clinicians’ understanding of more conservative and tissue-sensitive procedures enable dental professionals to offer patients esthetically pleasing restorations that have been observed to support healthy gingiva. These findings are likely the result of restorations that were placed to create an environment that allowed more control of tooth position, tooth shape, contact point, margin placement and interproximal contours.21-24
Of importance among such procedures is the creation of a margin that does not violate the sub-gingival environment, thereby aiding in the maintenance of a plaque free environment. Additionally, preservation or re-establishment of natural tooth contours and the proper margin placement prevent infringement on the biologic width. And, the use of non-metal substructures prevents discoloration of gingival tissues or potential hypersensitivity to the base metals.15,16,21
While it was observed that these factors most likely led to an improvement in oral hygiene and plaque removal,23 the treated patients exhibited heightened awareness of the need to maintain their teeth and the new restorations.25 At this point, more long-term in-vivo research is necessary to demonstrate a direct correlation between the placement of all-ceramic restorations and improved soft tissue esthetics and gingival health.OH
Thomas Trinkner, DDS, is a Clinical Instructor for the Esthetic Continuum at the LD Pankey Institute. He maintains a private practice specializing in comprehensive restorative and esthetic dentistry in Columbia, SC.
Paul Steigerwald, DDS, is a registered continuing education instructor for the California Dental Association and the Academy of General Dentistry. He maintains a private practice specializing in periodontics in Santa Rosa, CA.
Oral Health welcomes this original article.
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