Spruing Blog Series: Veneers, Maryland Bridges and Bridges



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.


Veneers have a very similar workflow as other restorations, bring it in with the inlay/onlay/veneer option. By default, the software will bring in the restoration in on the best angle to be milled out. Generally, if you have a tall enough puck, it will be brought in on the right angle so you can see everything from the exact top view and exact bottom view. When we are adding the sprus on veneers, only add the sprus on the buckle side for the most part. For number 8 and 9 we do need to place two sprus, but they can be 1.5 mm so there’s less to work on afterwards. We place the sprus pretty low because we are worried about the height on contour. If it was a different size veneer, we could add only one spru and have it come in as a 3mm spru so it has some extra support.

Maryland Bridges

When you have a restoration that doesn’t have a normal margin type, bring the restoration into the software with the inlay/onlay/veneers option. Position the angle of the bridge so it’s more vertical and double check that it can be milled from the top and bottom.  Always add sprus to the ponic, you may or may not need sprus for the wings, and you could add smaller sprus.


When bringing in bridges to the software, sprus are automatically placed and they’re usually on the contacts so we want to remove them. Using the same method as other restorations, we want to add the sprus to the height of contour but we don’t need to add them to every unit. Usually add the sprus to the buckle and lingual of every other unit. If you have an even set of units, add the extra set of sprus.  As a general rule of thumb for bridges, never add green sprus which are fully cut by the mill. If you want more support, you can add more sprus and make those green. Be mindful when placing additional sprus, we don’t want sprus on every unit because the spacing is so small and it might be hard to mill in those small areas.


This was the third and final installment of a three-part series on spruing best practices. Check out the first post about spruing basic restorations here or the second post about spruing onlays here, 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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