Milling Multicolored Zirconia
How to position for success in multicolored zirconia
By Ron Rosenthal, CDT
Mastering the materials and techniques of today's digital workflow allows laboratory technicians to achieve repeatable success and better control of their production. With many new materials being introduced to the market every year, this task can be challenging and control can seem elusive. Many laboratory environments don't realize the importance of what kind of CAD/CAM workflow they use and how they can optimize their milling results to produce an optimized outcome for their business. But, with the right tools, laboratories can achieve superior, efficient, and replicable results.
The digital workflow and the right tools assist your laboratory technicians and team in providing optimal results. Partners like exocad (exocad.com), 3Shape (3shape.com), and Dental Wings (dentalwings.com) provide a CAD environment in which to create accurate and esthetic zirconia restorations and fulfill the prescription requested (Figure 1). However, it is up to the laboratory to control the outcome from their machines by controlling their software file output.
These factors are determined through parameters from the design area, taking into special consideration the type of fit, form, and function being produced for the desired case. A good example of such parameters would be the cement spacer, additional cement spacer setting, or drill compensation ratio. Each material mills or reacts differently, and it is up to the techncian to utilize the design software's results to get the best-fitting unit from the mill.
When referring to workflow in the CAD/CAM department, a crucial part of the success is the CAM being used. There are many different computer-aided milling machines on the market today. CAM software takes all CAD design, parameters, and data, and processes this calculated information into the machine. The software prepares the STL information to go to the milling machine, with the appropriate cutting sequence or milling strategy provided within the CAM software. Without this information the machine would not know what to do or how to cut the desired material specific to the case.
The case described below was designed in exocad and nested successfully in WorkNC Dental CAM 2017 R2 software (WorkNC Dental; workncdental.com). The material used was priti®multidisc ZrO2 multicolor (pritidenta; pritidenta.us), a zirconia blank with an esthetic shade gradient already in the material. WorkNC Dental CAM software allows users to go from the simplest nesting to the most complex situations while offering the same ease of use.
WorkNC Dental CAM gives its users stable, repeatable, quality results with their mills. Multicolored zirconia cases need exact positioning in the block being used. This is essential to achieve optimal color and consistency. In this case, the exocad STL milling file was sent to WorkNC Dental CAM and nested into one of its many easy-to-use features for using multicolored zirconia. A variable-layer gradient block can be created by the user to nest and control the outcome of the color in the restoration.
As seen in Figure 3 and Figure 4, the laboratory used a pritidenta® multicolor blank for the case above. Dependable results can be achieved by positioning the units at the correct locations within the pritidenta material. In Figure 5, the chosen block was placed in the machine. Figure 6 clearly shows several single units that were placed in varying positions of the multicolored material, allowing for the correct color saturation of each unit. The bridge was positioned in the same manner and achieved a successful and consistent result.
With a successful digital workflow within the laboratory, each step plays an equally important role in the result—from designing to nesting in the CAM to milling the desired material. In this situation the final restoration was designed, nested, and milled in priti®multidisc ZrO2 multicolor (Figure 7 and Figure 8). This laboratory chose the right combination of tools for the control, consistency, and efficiency it needs to reliably produce high-quality cases.
About the Author
Ron Rosenthal, CDT, is the North American Business Development Manager of WorkNC Dental Cam by Vero Software, Southfield, MI.
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