Spruing Blog Series: Onlays



With the large variety of restorations that digital laboratories are now producing it’s essential to use best practices when performing the CAM operation. In this 3-part blog series, Razmig Tatoulian and Alex DeVos of the CAP/Zahn Support team will review step-by-step instructions for spruing the most common restorations, including screw-retained, Maryland bridges, inlay/onlays, and veneers.

Inlay/Onlay/Veneer Option 

Anytime you have an indication that doesn’t have a normal margin shape, it should be brought in with an inlay/onlay/veneer option.  When its brought in this way, it doesn’t have a margin line which means we need to double check the angles the software has brought everything in with.  We can double check the angles using the exact top view and exact bottom view-making sure you can see all the side walls. If you are not able to see a side wall, you should go into manual positioning and adjust the angle.

Adjusting Spru Width 

Now you can add sprus, the default for spru width will always be 2mm. For this example and most inlays and onlays it is not necessary to have 2mm sprus. You can change this by going into the settings menu with the gear, general configuration, change the interface to medium. This makes additional buttons and features available and means the workflow isn’t as automatic as it is for most users.

Using this medium interface when you click the add support pin button allows you to change the size of the spru. The 1.5mm spru is good for onlays when adding them on the contact. It will let you put a spru on the working area but that depends on your preference on what you want to grind away on after its milled.


This was the second of a three-part series on spruing best practices. Check out the first post, Spruing Blog Series: Basic Restorations (1 of 3) hereBe on the look out for the additional blog posts coming soon or check out our on-demand webinar, Spruing 101: Best Practices By Restoration Type.


Note: Please note that the workflows discussed in this blog are based on Sum3D Dental and Roland DWX 51D.  The approach and techniques discussed are based on our internal R&D, and can be used as rule of thumb for day-to-day operations.  Techniques and approaches you will see in this post can also apply to different milling systems such as Amann Girrbach or imes.

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