Nash Dental Lab Material Choices
At NDL 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 records appointment. 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. We offer the following materials to choose from:
Zirconia based restorations have become a restorative workhorse 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.
Best known by the trade names of BruxZir® or our ZirNash, monolithic Zirconia restorations have taken the dental world by storm! Since being introduced in 2009, there have been millions of 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 community. New developments in Zirconia technology have produced much higher translucency levels in this material. Moreover, internal shading of the Zirconia adds enhanced aesthetics to monolithic Zirconia cases and prevents the display of white Zirconia material if occlusal adjustments are required.
Cubic Zirconia A relatively new category of restoration is Cubic Zirconia. This option from the Zirconia family produces incredibly vital restorations; however, they do sacrifice about a third the flexural strength of their tetragonal cousins. 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 Esthetic 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 milled, stained, glazed and shipped with only minimal technical refinements being added. This is the cheapest and quickest way to produce these restorations. However, it is my opinion that it is far from the best way. Doctors object to these crowns being over-contoured and also the thick layer of glaze material that is common at the margins of these restorations as the glaze material will breakdown over time creating a rough matrix on which bacteria and plaque will accumulate at the margins.
At Nash Dental Lab we know that a natural emergence profile and hygienic margin can only be achieved by “hand-working” the restoration. This takes additional skill and labor to accomplish. We hand-work the margin area of our monolithic Zirconia cases in the pre-and post-sintered stages of fabrication to achieve a smooth polished margin. Our master ceramist uses a diamond wheel to put a high polish on the Zirconia in a 1-millimeter band 360 degrees around the margin. This eliminates the glaze in that area and produces a very hygienic restoration for your patients for the long-term.
Our porcelain layered Zirconia crowns and bridges have become our premier Zirconia 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 polished Zirconia. In the aesthetic zone we cut the copings or frameworks back by .3mm and layer 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 aesthetics, function and longevity. The Porcelain Fused to Zirconia (PFZ) crowns and bridges are ideal choices for cases with deep sub gingival margins, posterior bridges, especially dark dentin or metal posts and in long span implant applications.
Time has proven layered Zirconia restorations to be an excellent choice for most crown or bridge applications. As with PFMs our layered Zirconia restorations have a feldspathic porcelain outer layer for aesthetics. For more than 15 years, we’ve offered layered Zirconia restorations and find that the durability is very good, similar to PFMs. Zirconia restorations also provide a very aesthetic result over dark or severely discolored dentin. However, as with any all-ceramic restoration we suggest you provide us with the shade of the prepared tooth so that we can use this information to finetune the overall shade of the restoration.
There are 2 dominant players with this material today. Ivoclar Vivadent's pressable lithium disilicate material (IPS e.max®) 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 during his in vitro study. The second material is from GC America. Their brand name for it is LiSi Press. Both materials are 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. Both IPS e.max and LiSi Press work well at a minimal thickness for veneers; they work equally well as full crowns on molars, and everything in between. Lithium Disilicate is etchable and should be bonded with your choice of resin cement. A popular 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. LiSi Press, a lithium disilicate material from GC America, is rated at 500 MPa. We find that the marginal fit is superior with pressing as opposed to milling the IPS e.max. For this reason, we us the “press method” with both systems.
This type of restoration has been used for decades and provides some of the nicest aesthetic 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 (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 the dark or stratify uneven shade. 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 veneers as that is where they tend to break. The development of lithium disilicate pressable restorations have replaced feldspathic veneers in very thin veneer applications and pressed ceramics in general is better to control extensive cases with full arch occlusion. Simple anterior veneers without excessive thickness or areas of unsupported porcelain can be done very successfully with feldspathic ceramic.
PFM restorations are still used in many long span bridges and implant applications. Nice aesthetics 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, making it our option of last resort.
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.