Nash Dental Lab Material Choices
At Nash Dental Lab we offer only the finest restorative materials to achieve beautiful long-lasting results for your patient. We understand that selecting the right treatment option and material will begin with your patient's appointment. If asked, we can help you optimize your choices in providing your patient with the best long-term solution that will accomplish your goals without compromising either aesthetics or function. By providing the best material choices to compliment your treatment plan for each patient we are able to provide you with the least invasive options. Our choices of material include the following:
Zirconia restorations have become the restorative workhorse preferred by clinicians over the last 15 years. Applications include full crowns, bridges and implant restorations. Zirconia cases require a similar preparation and the same reduction requirements as Porcelain Fused to Metal (PFM) restorations (ideally 1.5mm axially and 2mm occlusally). However, with these high-strength ceramic restorations it is important to round any internal line angles (as with any all-ceramic restoration) and eliminate undercuts so that your die can be properly scanned in our laboratory.
The majority of clinicians tell us that they utilize conventional cementation for their Zirconia cases. Flexural strength of our Zirconia is 1200 MPa, which provides excellent durability for almost any crown or bridge application. As with PFMs, our Porcelain to Zirconia restorations have a polychromatic ceramic overlay for aesthetics. Over the 12 years that we’ve offered these layered Zirconia restorations, we find that the chipping or failure rate of this porcelain is very low, similar to PFMs. As is also the case with PFMs, Zirconia restorations provide a very aesthetic result over dark or severely discolored dentin.
Nash Dental Lab offers: BruxZir®, ZirNash and 3M’s new Lava Esthetic Crowns and Bridges
In a similar fashion as IPS e.max monolithic restorations that I’ll discuss later, monolithic Zirconia restorations have “taken the dental world by storm!” Since being introduced in 2009, there have been more than 5 million BruxZir restorations placed in the US alone. The incredible durability, moderate to good aesthetics and latitude to use monolithic Zirconia in areas of minimal reduction have created a demand previously unmatched in the dental industry. New developments in Zirconia technology have produced much greater translucency in this material which allow for greater vitality. Moreover, internal shading of the Zirconia mill stock adds to enhanced aesthetics of monolithic Zirconia cases and prevents the show through of white material if occlusal adjustments are require.
An example of esthetic improvements in Zirconia technology for monolithic restorations is 3M’s new Lava Esthetic material. 3M has successfully developed this cubic Zirconia to rival monolithic IPS e.max in translucence and vitality while maintaining impressive strength. At 800 MPa of flexural strength Lava is twice as strong as pressed (400 MPa) or milled (360 MPa) IPS e.max. Moreover, Lava Esthetic is the first Zirconia with inherent, tooth-like fluorescence, so it maintains its natural appearance under a variety of light sources.
Most inexpensive, monolithic Zirconia restorations are stained and glazed. This is the cheapest and quickest way to produce these restorations. However, it is my opinion that it is far from the best way. Very high wear rates of opposing enamel can occur from unpolished, glazed monolithic Zirconia restorations. Moreover, the staining and glazing processes increases the opacity of the zirconia restoration which decreases vitality. At Nash Dental Lab, we use a much different process for our BruxZir and ZirNash restorations. We begin with FDA cleared internally shaded Zirconia. After our design and milling work, we utilize stains which penetrate into the unsintered Zirconia to enhance the vitality of the restorations in a similar way as a natural tooth. See chart:
The Noritake Porcelain to Zirconia crowns and bridges have become our premier all-ceramic option because they have the advantages of durability and aesthetics. The improvement in the shading and translucency of our Zirconia pucks (mill stock) allow us to achieve excellent aesthetics with traditional crown and bridge preparations. To optimize the strength of these restorations, we leave all structural and load-bearing areas entirely in shaded and highly-polished Zirconia. In the aesthetic zone we cut the copings or frameworks back by 1mm and layer them with Noritake CZR for a strong and beautifully vital restoration. This takes a high level of technical expertise and significantly more time, but is the best possible way to achieve maximum aesthetic, function and longevity. The Porcelain Fused to Zirconia (PFZ) crowns and bridges are ideal choices for cases with deep sub-gingival margins, posterior bridges, cases over dark preps or metal posts and in long span implant applications.
Ivoclar Vivadent's pressable lithium disilicate material started the monolithic restoration revolution back in 2009 after a study by Dr. Van Thompson of New York University was published showing the impressive durability that IPS e.max demonstrated in the monolithic crown design. The material is a relatively high strength ceramic that can be pressed as thin as .2mm and comes in a variety of opacities to provide excellent aesthetic results in a wide variety of clinical applications. It works well at a minimal thickness for veneers; it works equally well as a monolithic full crown on large molars, and everything in between. It is etchable and should be bonded with your choice of resin cement (A good option to use is the Multilink from Ivoclar). Because we press (instead of mill) IPS e.max, you receive restorations with a flexural strength in the 400 MPa range. Milled IPS e.max yields a maximum strength of 360 MPa. We also find that the marginal fit is superior with pressing as opposed to milling e.max. We are sometimes limited by the some color options in the IPS e.max system, which may result with our recommendation of Noritake CZR Press (a Lucite reinforced ceramic like IPS Empress®, but better) or a feldspathic ceramic for some veneer cases. Although this material is great for single units, it does not have the strength for multiple unit restorations.
This type of restoration has been used for decades and provides some of the nicest esthetic results ever achieved in dentistry. They are fabricated with a powdered ceramic buildup on a high noble foil or refractory model. Fits are good and color is excellent! These restorations must be cemented adhesively to be successful in the long-term. Our doctor clients tell me that a total etch and a 4th generation dental adhesive (such as Optibond FL) and a resin cement (Variolink by Ivoclar or Insure by Cosmedent) provide the best latitude for shading modifications and durability. Varying levels of opacity can be built into these restorations to mask dark or uneven shades of the underlying prepared tooth and to create very nice contact lens margin effects. However, do remember that a more aggressive preparation is required to provide us with the space to fabricate a thicker (eg .5mm) veneer which will cover a dark or uneven prep shade of a tooth or teeth. Flexural strength of feldspathic ceramic is around 85mpa; however the longevity of this material can be excellent once it’s bonded to the underlying tooth structure. The limiting factor on use of this class of material is the low strength, which isn’t conducive to large areas of unsupported porcelain that occur in complex clinical situations. Also be very careful when trying in and cementing these veneers as that is where we see them broken. The development of lithium disilicate pressable (IPS e.max) restorations have replaced feldspathic veneers in very thin veneer applications. Anterior veneers without excessive thickness or areas of unsupported porcelain can be completed very successfully with feldspathic ceramic.
PFM restorations are still used in many long span bridges and implant applications. We are proud to have Lori, our substructure specialist, with over 20 years experience in the field to ensure ideal framework design. Nice esthetics with PFM restorations are possible if adequate reduction is accomplished and wide shoulders are prepared for porcelain margins. This class of restoration is the least conservative of natural tooth structure.
Remember that Full Gold Crowns (FGCs) were the first monolithic restoration! Excellent function is often achieved long-term with these crowns, bridges, inlays and onlays. The only problem with these FGCs is that they are not tooth colored. We frequently use them on second molars in full mouth reconstructions. I feel that Zirconia and IPS e.max restorations now fill most of the clinical requirements previously indicated for gold.