• Your choice of processing pathway- Mill and Fire and Polish - provides workflow flexibility and processing freedom with every case
  • Clinically proven strength for long-term clinical confidence
  • Chameleon effect for highly esthetic restorations

Listen to what our doctors say.

Dr. Conte

"The first true high strength glass ceramic that offers the option to polish only or fire in the oven for additional strength...it's very unique in the market." 

                            Dr. Bob Conte

Dr. Pasicznyk

"The strength is more than adequate, the esthetics are wonderful, it's very fast, very efficient and gets done very quickly." 

                        Dr. John Pasicznyk

Dr. Hall

"Celtra Duo covers a very broad spectrum of clinical indications. The advantage is we can work quickly, saves us time, makes us more efficient."

                              Dr. Andrew Hall

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The proof is in the block

The proof is in the block


Of 345 dentists surveyed, dentists rate "processing flexibility" as their #1 benefit of Celtra Duo (ZLS), with "margin quality" coming in a close second!


Lanmark360. “Celtra Duo (ZLS): CAD/CAM Blocks.” Survey. 6 January 2016.

Block Science

The science behind the block

The science behind the block

Learn more about Celtra Duo (ZLS) and the recommended ways to handle the material in clinical application.

Self-healing for greater strength and durability

The high glass content of Celtra Duo (ZLS) not only gives the material its excellent light-optical and mechanical properties, it also provides the added benefit of self-healing when fired.

During the firing cycle, as the glass transition temperature is reached, the glass ceramic turns into a highly viscous "liquid"; however, not viscous enough as to lose the shape of the restoration. Rather, the viscous glass fills any flaws caused by the milling process. After firing, having gone through the self-healing stage, as the material cools to room temperature, it hardens back to its original high strength.

The importance of correct handling

Preparing Celtra Duo (ZLS)

The preparation requirements of Celtra Duo (ZLS) are similar to other all-cermic restorations. Clinicians should aim for 1.5mm to 2mm of occlusal reduction with at least 1mm of axial reduction.

As with all CEREC restorations, the margins are the most critical part of the preparation and should be smooth and polished. Any milled restoration requires smooth polished margins so that the milling unit can adequately mill Celtra Duo (ZLS) restorations with ease.

When using the CEREC SpeedFire furnace, place the restoration directly on the firing pad. Note that the pad will need to be trimmed to fit.

No special equipment is needed, as Celtra Duo (ZLS) can be fired in standard ovens. However, Celtra Duo (ZLS) has its own unique firing schedule that must be programmed prior to firing. Firing schedules can be found here:

The importance of correct handling

Preparing Celtra Duo (ZLS)

The preparation requirements of Celtra Duo (ZLS) are similar to other all-cermic restorations. Clinicians should aim for 1.5mm to 2mm of occlusal reduction with at least 1mm of axial reduction.

Excellent edge stability

Excellent edge stability

Celtra Duo (ZLS) provides excellent edge stability, resulting in restorations with strong and durable margins that resist chipping.  In testing, standardized copings are cut back at the edges to a wall thickness of 200µm to examine edge stability.

The results speak for themselves.

High strength and longevity

Celtra Duo (ZLS) retains its high level of strength in long-term chewing simulations. Even after 6,000 thermal cycles (41°F to 131°F) and 1.2 million chewing cycles with 70 Newtons of force, Celtra Duo (ZLS) demonstrated no loss in strength.

Natural opalescence

Natural opalescence

The unique lithium silicate crystalite composition of Celtra Duo (ZLS) with 500-700µm particle size contributes to an opalescence that behaves like natural tooth enamel, creating a lifelike appearance and vitality in the mouth.

Fluorescence and chameleon effect

The high light conductivity and shade adaptation of Celtra DUO (ZLS) in conjunction with the remaining natural teeth and the pronounced opalescence create the desired chameleon effect.  With an inlay, for example, it's virtually impossible to discern where the restoration ends and the natural tooth begins. Likewise, full contour crowns are virtually undetectable among neighboring natural teeth.

Mill & Fire



Characterization and firing technique

Fired restorations have a strength of 370 MPa.

Mill & Fire

1 Before applying the stain and glaze material, remove all dirt and grease from the restoration.

2 Mix glaze in jar thoroughly with a spatula if separation is seen.

3 Remove desired amount of Celtra Duo Universal Glaze paste from jar to tray.

4 If a different consistency is desired, adjust the consistency by diluting the material with Celtra Duo Universal Stain & Glaze Liquid.


5 Apply a thin layer of glaze material all over the crown surfaces using a staining brush. Make sure not to apply the glaze material either in too thick or too thin of a layer. A thin layer will result in a matte finish. A thick layer can result in a puddling or pooling of a stain.

If customization is needed, take a little of the corresponding body and incisal stains and position it on the tray.

7 Dilute if needed and apply it to the crown.





8 Position crowns directly on the firing pad and fire according to the firing instructions.

After the first firing, if the consistency of the glaze was too thin, the restoration may come out under-glazed. If that is the case, apply a thin layer of Celtra Duo (ZLS) overglaze material all over the crown surface using a brush. Once the overglaze is applied, conduct firing procedure according to the Celtra Duo (ZLS) Firing Schedules.

Mill & Polish

Simplicity in processing

Milled restorations have a flexural strength of 210MPa after polishing

After the restoration has been milled, start with a diamond

After the restoration has been milled, start with a diamond

1 Use a fine grit diamond in a friction grip slow speed handpiece ONLY to remove the excess from the mill. An electric handpiece is more effective than one that is air driven.

2 Run the handpiece at a low speed (max 12,000 RPM). Avoid a high-speed handpiece because it will create excessive heat and trauma to the ceramic.

Next, use a rubber porcelain polisher, as follows:

1 Use a medium grit rubber wheel of your choice.

2 For the occlusal surface, use a point shape.  An electric handpiece should run at 10,000 RPM to a maximum or 12,000 RPM, with only light pressure. Electric handpieces have constant torque even at a slow speed, so they are more effective than air driven handpieces. Begin the process with the medium shine wheel.

3 Next, use a fine wheel and/or point shape with the same technique described in Step 2.

4 Finish with a fine grit rubber wheel.

5 For an effect high shine, use polishing paste. Polishing paste should be used with a bristle brush wheel in a slow speed latch handpiece. This is very effective for polishing grooves in the posterior anatomy.

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