Improve Zirconia Restorations: From Preps to Polish

mm Written by Andrew Sedler

Zirconia Restorations: Precision Fits, Strength, and Durability

Matching The Single Unit: Layered Zirconia

The versatility of zirconia restorations continues to expand with the development of new shades and translucencies. As a result, zirconia has improved significantly in recent years and is more closely resembling real dentition than ever before. In addition to its excellent aesthetic properties, zirconia also offers precision fits, strength, and durability. This restorative option offers a number of ways to improve success rates.

Zirconia Tooth Preparation Design

Are PFMs Still a Viable Treatment? Zirconia vs. PFM

The biggest factor in achieving the best results with zirconia restorations is understanding the appropriate preparation design. Some universal requirements help to create the perfect zirconia preparation. Those requirements are as follows:

  • Providing enough reduction on the tooth is imperative to providing excellent esthetics.  
  • The tooth must be prepared to provide a passive fit for the restoration. 
  • Tooth reduction should be uniform to ensure strength and longevity. 
  • There should not be any sharp edges on the tooth preparation. Sharp edges can cause unnecessary stress on the crown resulting in fractures.
  • Digital impression techniques are more accurate when the preparation is smooth.

These general preparation guidelines are standard for most ceramic restorations. There are more specific requirements for zirconia restorations that must also be followed.

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Layered Anterior Zirconia Crown Preparation Parameters

  • There must be adequate room for a minimum of 0.3 mm wall thickness. 
  • Incisal edge reduction should ideally be between 1.0 mm and 2.0 mm.
  • Gingival margins should have a chamfer design with at least a 0.5 mm reduction.
  • Make sure the preparation is performed with no undercuts.
  • Make sure not to create a bevel. 

Layered Posterior Zirconia Crown Preparation Parameters

  • There must be adequate room for a minimum of 0.5 mm wall thickness.
  • The occlusal reduction should ideally be between 1.0 mm to 2.0 mm
  • Gingival margins can have a chamfer or shoulder design with at least a 0.5 mm reduction.
  • The preparation should be tapered between 4° and 8°.
  • Make sure not to create a bevel.
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Monolithic Zirconia Crown Preparation Parameters

Increasingly, monolithic zirconia crowns provide an excellent material choice. As a result of grinding and clenching, these restorations are strong enough to withstand these forces. This is particularly true in patients suffering from bruxism or limited occlusal clearance.

To prepare for full contoured restorations, follow these steps:

  • To provide adequate occlusal anatomy, the occlusal should have a depth cut of 1.0 to 2.0 mm.
  • The functional cusp tip should be reduced by 1.0 to 1.5 mm.
  • The gingival margin should have a chamfered design with a reduction of 0.5 mm.
  • There should be a 4° to 8° taper to the axial wall.
Improve Zirconia Restorations - Burbank Dental Lab
Improve Zirconia Restorations - Burbank Dental Lab

Once the case is prepared, it is ready to be impressed and sent to Burbank Dental Lab for processing.

Chairside Adjustments of Zirconia Restorations

Zirconia restorations, as with other types of ceramic restorations, may require adjusting during insertion. When it comes to adjusting and polishing zirconia restorations, several great products can help.

To begin with, determine if a diamond is required for the adjustment. A diamond bur is only necessary when a significant adjustment is needed. Abrasive polishing wheels or points can be used if only minimal adjustment is required.

Following are some rules to follow if you determine that a diamond will be needed to accomplish the necessary adjustment:

  • Slow-speed friction grip handpieces are recommended.
  • Diamonds with fine grit are best. 
  • Run at 20,000 RPM with plenty of water.
  • Avoid excessive heat by keeping your touch light.

Almost all abrasive companies sell diamonds specifically for zirconia adjustment, including Brasseler, Comet, Axis, and others.

Improve Zirconia Restorations - Burbank Dental Lab

It is essential to use a fine diamond bur suitable for zirconia restorations if adjustments are needed.

Zirconia can be micro fractured by too much heat or sparking during an aggressive reduction. Heat must be reduced as much as possible by using as little pressure as possible.

Keeping the restoration cool is also made easier by using water while adjusting.

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Chairside Polishing of Zirconia Restorations

When adjustments are made chair-side, it is easy to polish zirconia, creating an exceptionally smooth surface. It is important to have a highly polished surface on zirconia restorations.

Achieving an adequate surface polish requires the use of abrasives that have been designed to be used specifically for polishing zirconia. When using the correct instruments, achieving the desired polished surface is accomplished with less effort. Abrasive manufacturers have specialized products for zirconia, just like diamonds.

Polishing Zirconia involves a two-step process:

  1. The medium/smoothing abrasive should be used first. When you begin at a slower speed (5,000 RPM), use medium pressure, and as you move up the speed, use light pressure. (See figure 4 below)
  2. Next, use a fine polishing abrasive to achieve a highly polished surface. To buff it out to a high shine, it’s typically done at high speed (15,000) with a light touch. (See figure 5 below)

Figures 4 and 5

Improve Zirconia Restorations - Burbank Dental Lab
Improve Zirconia Restorations - Burbank Dental Lab

This procedure will deliver a very effective polish intra-orally in a very short period.

Improve Zirconia Restorations - Burbank Dental Lab

Time-Tested Restoration Techniques

Improve Zirconia Restorations - Burbank Dental Lab

The preparation design of any restoration sets the foundation for the overall success of the case.

Following the parameters set forth by the material manufacturers helps to ensure the best fit, longevity, and esthetics for the restoration. Using time-tested techniques chairside will help make the inevitable adjustments smooth, effective, and fast.

To get help with your next case, click the blue icon along the bottom right-hand corner or call (800) 336-3053.

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Fabrication
of the future
is here!

Burbank Dental Lab has three new state-of-the-art Carbon M2 printers. We are very excited about the options that these cutting-edge printers will allow us to offer our dental clients. Here are some of the advantages that these printers will begin to deliver to you and your dental practice.

Our New
State-Of-The-Art
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Carbon offers a highly dependable 3D manufacturing solution for many dental applications with its breakthrough Digital Light Synthesis™ technology, enabled by a wide range of dental materials.