Classic White Zirconia vs. Pre-Shaded colored Milling Discs

Classic White Zirconia vs. Pre-Shaded colored Milling Discs

Which product wins the quality, efficiency, and cost battle?

As the Sales & Marketing Manager at AmericaSmiles, I speak with hundreds of different lab owners during the year.  I’ll have a couple of thousand verbal conversations and probably twice as many email correspondences.  This vast amount of dialogue provides me with an awareness of the practices, questions, and concerns of the average US dental lab.

Since the opening of the AmericaSmiles Zirconia manufacturing plant, I have had a large number of conversations about the pros and cons of the many Zirconia options and brands.  Most often discussed are the advantages and disadvantage of the Classic White vs. Pre-Shaded milling discs.  While some labs mill strictly white, others are strictly shaded, and some mill a combination of both.  Although multi-layered (gradient shade) Zirconia is receiving growing attention, for the sake of this article, we are discussing strictly classic white vs. pre-shaded discs.

Lab owners are seeking to satisfy three basic criteria when choosing a zirconia disc:

  • Quality and Consistency of the final glazed product
  • The efficiency of the manufacturing process
  • Cost of the Zirconia Discs

I spoke with Keith Crittenden the owner of AmericaSmiles about my discussions with lab owners in regards to this subject.  As the CEO of one of the largest dental lab networks and an early participant in cad/cam dentistry, he has taken a hard look at the cost/quality benefits of the Classic White discs vs. Pre-Shaded zirconia.  Keith identified several specific areas that are not often properly considered when choosing between Classic White and Pre-Shaded discs. We decided to ask Keith to compare Classic White zirconia discs to Pre-Shaded Zirconia discs in each of the three areas noted above and here are his opinions:

1. Quality and Consistency of the Final Glazed Product Winner is: “A Tie”

  • Quality of the final glazed product goes to: “Classic White”
  • Consistency of the final glazed product goes to: “Pre-Shaded”

Quality:

The Classic White zirconia disc offers the dental lab technician a pre-sintered “Blank Canvas” to create a life-like dental restoration. With incisal tone and inhibitor kits such as the AMS Incisal Tones product, the lab technician can build all the character traits they desire into every tooth they color. This process gives the technician the greatest ability to acquire the most natural transition from the gingival shade to the incisal shade. With every tooth having its own shape and height the technician can characterize the pre-sintered tooth to meet the appropriate requirements. The subtle downside to this process is that because each crown has a very different total mass of zirconia there can be some inconsistencies with the way the zirconia absorbs the colorant, leaving the post-sintered tooth too light or even worse, too dark.

Consistency:

The pre-shaded disc offers the technician the most consistency in terms of acquiring an accurate post-sintered base shade. That statement is assuming good manufacturing practices are followed by the zirconia disc manufacturer. But this consistency of the base shade comes at the cost of having no blend transition from gingival shade to incisal shade. This must be accomplished at the lab bench.

Summary:

We consider this category a tie. Although the classic white has the best potential for the best final product, we also need to consider the benefit that pre-shaded offers for consistency.

2. Efficiency of the manufacturing process winner is: “Classic White”

In coming to our conclusion we considered the following factors:

  • Group Nesting and Milling… advantage classic white
  • Post Processing Calculation Times…advantage classic white
  • Mill Swap-out/Set-up Times…advantage classic white
  • Post-Milling Labor Times…advantage pre-shaded

Group Nesting and Milling:

With classic white, the lab technician only needs to sort and nest by tooth height. This allows the technician to group more teeth together in one disc for more efficient nesting times and more efficient milling times. Every time you start a new nesting project it costs you time to load the required disc and save a new file. Your mill also mills more efficiently due to fewer machine tool pick-ups while milling larger groups.

Alternatively, with pre-shaded discs, grouping by height and shade means more nesting loads and smaller machine runs. Both of these add to the inefficiency factor. When your machines are capable of milling at a rate of $300-$400 dollars, every 15 minutes of inefficiency costs your lab $75-$100.

Post Processing and Calculation Times:

At the end of every nesting sequence, the lab technician must run the post-processing calculation to create a file the mill can read. We have found that smaller groups of nested teeth add to the inefficiency factor. Here is an example of what we mean: Nest only one tooth and the post processor might take 2-5 minutes to calculate depending on your specific nesting software. Nesting 10 teeth DOES NOT add 10 times to the post-processing calculation times. The more teeth you nest, the less time ‘per tooth’ is required to run post processing. The more teeth you nest per time, the less time per tooth required. We also find that technicians tend to walk away during the post-processing. The computer may sit unattended for several minutes once the processing is complete. The more nesting solutions per day, the more the computer sits idle at the end of each run. Nesting larger groups of 6-10 teeth at a time is most efficient, and only possible with classic white.

Mill Swap-out/Set-up Times:

Smaller groups of nested discs require more attention. We have found that mills tend to sit unattended once the mill has completed its milling cycle. Smaller groups mean more disc swap-outs/set-ups which take more man-hours and increase the chance for the mill to sit unattended waiting for the disc to be changed out. Larger runs make your mill more efficient and require less human attention. This is only possible with classic white.

Post-Milling Labor Times:

This is the one area where pre-shaded has the advantage. Once the tooth has been separated from the disc, it only needs to be cleaned of all dust and it is ready for the oven. The classic white, on the other hand, must be sorted by shade and then colored. In our milling center, sorting and coloring takes 75 seconds per tooth. Assuming 40 crowns per day, this only adds one hour of labor to the lab technician. We believe this one hour is easily offset through the efficiencies gained in nesting and milling.

Summary:

We believe that Classic White wins the overall efficiency evaluation even with the added labor of coloring by hand, which we also find saves time at the final stain and glaze procedure. The efficiency from file sorting, nesting, post-nesting processing, and milling machine disc changes makes Classic White the clear winner.

3. Cost of Zirconia Discs winner is: “Classic White”

  • Per Disc
  • Total Inventory Requirements

Per Disc Cost:

Classic White vs. Pre-Shaded cost per disc clearly goes to classic white. The average cost difference of a 98mm x 12mm disc is about $15 per disc. This raises your cost for one pre-shaded tooth by about $1. By comparison, a Classic White tooth absorbs about (20 cents) worth of coloring liquid per tooth. At 40 teeth per day this will cost your lab over $8,000 per year or about $700 per month.

Total Inventory Requirement:

Classic White only requires that you inventory the varies thicknesses of discs. To inventory Pre-Shaded, you must inventory the varies thicknesses and the various shades in combination. Although the Vita Classic shade guide has 16 shades, we find that the average lab keeps about 10x’s the amount of Pre-Shaded Zirconia stock than that of a lab using Classic White. With an average disc price of $100ea, your cost to inventory a one month supply of discs is considerably higher with Pre-Shaded. A lab that mills 40 teeth per day in Classic White needs about $4,000 of inventory for one month. By comparison, a lab doing that same volume will often have as much as $40,000 worth of partially used discs in their inventory.

Summary:

It is considerably less expensive to mill in Classic White vs Pre-Shaded allowing you to reduce your total cost of production.

 

Article Summary:

Using pre-shaded discs only provides you with the benefit of a consistent Chroma Color in the gingival 1/3 of the tooth along with the ability to go straight to sintering post-milling. Classic White offers you the best opportunity to achieve a more natural appearing restoration with a transition from Chroma Effect to Enamel Effect.

Classic White is more efficient during the Nesting, Post Processing, and Mill Swap-out/Set-up processes.

Classic White is less expensive per disc and requires less total inventory.

Clear Winner: Classic White.