An abundance of newer crown and bridge materials have become widely available to the dental clinician in the USA over the past dozen or so years. These materials have opened up a new era of vitality as well as strength for indirect dental restoratives that signals a golden age in this type of prosthetics that include: composite metals, pressed ceramics, zirconia and glass polymers. Their uses encompass traditional crown and bridge applications along with veneers, inlay/onlay cases and implant restorations. While many of these systems are implied to be appropriate for all clinical situations, it has been my experience that certain cases are more suitable to some of them than others.
For single crowns, I have found Captek and Ivoclar Vivadent’s Empress to be my materials of choice where esthetic concerns are paramount. Empress is a highly biocompatible, leucite-reinforced pressed ceramic with a translucency that allows the natural color of the underlying prepared tooth to reflect through the material. Under optimal conditions, it can afford unsurpassed esthetics (Figure 1: Which tooth in this smile has been restored with an Empress crown? See the end of this article to find out).
Other pressed ceramics on the market that demonstrate excellent esthetics are Dentsply’s Finesse, and Pentron Clinical Technologies’ OPC. Captek is a composite metal, not an alloy, that, when used as a porcelain substrate, mimics the optical properties of the tooth structure underlying enamel. It is applicable in a wider variety of conditions (with respect to occlusal loads, parafunctional habits, discoloration of underlying tooth structure etc.) because of its strength, toughness and masking ability. Its unique bacteriostatic properties promote periodontal health, and studies have shown that surrounding gingivae appear more natural with Captek crowns as compared to other restorative materials. Empress ranked second in this data with regard to gingival color.
In my experience, with all other factors (skill of lab technician, quality of clinical records etc.) being equal, it is easier to attain the highest level of esthetic excellence with Empress. However, in the hands of a superior ceramist, an ultimate esthetic result can also be achieved with Captek (Figure 2: Which tooth is restored with a Captek crown? See the end of this article to find out). Bonding is recommended when placing Empress restorations whereas Captek units can be conventionally cemented.
In practical terms, I choose Empress for cases in which I have no misgivings about occlusal or parafunctional issues, where I can keep my margins at or above the free gingiva (to facilitate bonding) and when there is no discoloration of the underlying tooth structure (as can be common in non-vital teeth) that can reflect through this material and compromise my esthetic result.
Correspondingly, if excessive wear is present, the presence of decay or extant restorations dictates subgingival margins or significant discoloration of the teeth to be prepared exists, I employ Captek. Both materials can be used for short span bridgework, but Empress is not recommended further back than the first premolar, whereas Captek can be used at any position in the mouth.
Zirconia crowns (such as Nobel Biocare’s Procera, 3M ESPE’s Lava or Dentsply’s Cercon) are metal-free crowns with a higher degree of strength than pressed ceramics, but I have not found them to be quite as esthetic, especially in terms of translucency and opalescence. These two factors, more than any others in my opinion, contribute to the perceived vitality of such restorations. Their strength, however, does allow for use as single crowns in molar areas and for bridgework comprised of all posterior teeth (Figure 3: Lava bridgework on the maxillary posterior) where a metal-free restoration is desired.
Biocompatibility for these crowns and bridges is also excellent and they can be either delivered with conventional cementation or bonded in place. If the patient’s mantra (or the doctor’s for that matter) is “metal-free”, zirconia based materials offer a versatility that is unmatched in the all-ceramic category.
As many patients now try to avoid display of metal (including gold) anywhere at all in their mouths, and many dentists are not satisfied with the clinical performance of the direct alternatives for restoring the occlusal surfaces of posterior teeth, tooth colored inlay/onlay restorations have come to the fore. While ceramics can be used for inlay/onlay cases, a class of modified indirect resins more properly known as glass polymers has emerged as the material of choice for this purpose. Materials such as Ivoclar Vivadent’s Concept, Kerr’s BelleGlass and 3M ESPE’s Sinfony provide for a more anatomic form, proper proximal contours as well as contacts, greater marginal integrity and better wear resistance than do their direct counterparts while being more esthetic at the same time (Figures 4: Posterior direct composites can be unesthetic & Figure 5: A belleGlass glass polymer). Glass polymers also exhibit a superior absorption of occlusal forces as compared to all ceramic materials. Though some manufacturers of glass polymer systems also promote them for individual anterior crowns, in my opinion the pressed ceramics are a better alternative for metal-free single units, but they can be useful for implant crowns due to their absorption of occlusal forces.
In the end, the myriad choices that dentists have with respect to these new, esthetic materials that have become available on the market in recent years can be daunting, if not overwhelming. Each has specific circumstances in which it is most suitable and will be among the best options. But just as one size does not really fit all, no single material is the panacea for all the esthetic challenges that we as clinicians see in our offices on a daily basis. It is for the discerning dentist to understand the qualities and limitations of each material and then decide which one best suits the needs and desires of his or her patient in their unique situation. Once we have become adept at making this decision, the clinical outcomes that can be realized will not only be functionally correct, but will result in esthetics that are truly dazzling to our patients. And what could be any more satisfying than that?
In Figure 1, tooth #8 has been restored with an Empress crown. In Figure 2, tooth #13 has been restored with a Captek crown. Biotemps Dental Lab. Lab work by Arrowhead Dental Lab.