Jeffrey Caso In a recent blog I spoke about turning on the working model at the mill preview screen to aid in the accurate placement of the sprue. This works great and helps to avoid placement in the contact areas. To further refine that concept, I would like to show how using the Slice tool will help you choose the thickest portion of the restoration to place the sprue.
Milling a restoration with the sprue placed in a thin area can cause a fracture to occur at the margin. This can be a real headache but is easily avoidable. On the Mill Preview screen, orient the restoration so you are looking at it from the occlusal or incisal view. From the side bar, choose Analyzing Tools and then select Slice. The restoration will be cut right to the level of the sprue just about every time. Ignore the red warning, which is telling you that the restoration is at the edge of the block.
You will now see exactly where the thin areas are and you can rotate the restoration so it will be at the thickest area on the restoration. If you really want to be fancy, combine this with the concept in my other blog on sprue placement. By turning on the working model, you can now place the sprue at the thickest area on the restoration and avoid the contact as well.
Spending an extra minute here can save you some time and money later.
