Today I would like to share with you my technique of preparing digital restorations created in Exocad for pressing.

This allows one to:

• Save time not needing to sprue restorations manually.
• Have better surface finish on full shapes, since the restorations are not printed on the supports but rather the sprue acts as one big support.

The advantages of my technique are the following:

• The original Exocad project and the restorations are unaffected.
• Everything is done within Exocad no need for additional programs.
• The mesh is topologically correct without any open faces or self intersecting geometry, resulting in nice printing without any artefacts.
• It's very quick and predictable.
• One is able to save the final additional pressing project and have the documented steps if he/she ever needs to go back and review/check.

The files

You can download the necessary files to follow my procedure here. I will keep the link updated with the latest version.

Designing

Once you download the attached files save them some place from where you will be creating copies of it. Next copy (don't move but copy) the printing press .dentalproject file to the patient's folder in CAD-data. I like having a record of what I've done and always being able to go back and check.

Once you open the printing press file you are greeted with this screen. Since we are doing expert things, immediately switch to Expert mode 😉.

Go to Tools>Add/Remove Mesh. Make sure your mesh type is "Generic Visualization Mesh"

and add all of the restorations you want to attach.

You can load multiple restorations at once, just make sure to keep the meshes individual once the pop-up asks you.

In the file tree one can toggle the visibility of the positioning limits. There are both limits for the small (100 g) and large (200 g) Ivoclar cuvette system.

Position the loaded meshes one by one. The bottom limit is set 3 mm from the printing base, like Ivoclar's instructions recommend. I adhere to this limit the most, in order to minimize my chance of failed pressings due to the sprues being to long and causing to much resistance. I find that I can cheat a little bit on the lateral limits by going slightly out of boundary on the small cuvette and still get good pressings. The limit is set 10 mm from the outside wall like the instructions recommend but I often go 8 or 7 mm from the outside wall and still not getting any cracks in the investment material.

Once positioned close the "Add/Remove Mesh" window and go to "Free-form". Under "Attachment" tab in the library drop down select "Load from file ...". Here one chooses the Printing Sprue supplied in the original folder that I provided.

The sprue is positioned so it fully intersects the printing base and the crown. If the sprue is too short it can be scaled only in it's length with the "Scale" mode without pressing any modifiers. It's important not to hold shift or ctrl otherwise it deforms and scales in it's diameter as well.

After attaching all of the sprues one by one, check if the sprue protrudes to the inside on any of the crowns. This can be remedied by reworking the protruding edge with the brush. It doesn't have to be pretty since we're attaching a crown on this end in the next step anyways.

Now again under "Attachment" tab load from file the crowns one by one.

A little known fact is that one can open And Make use of the "Align Meshes" function even when performing other steps like attaching a crown. So once the crown loads as an attachment, we are going to align it to our already positioned Visualization mesh by marking 3 common points and performing the best fit matching algorithm afterwards.

You can now smooth the transitions between the at the end of the sprues. Be carefull not to deform the crown margin because Exocad isn't protecting it in this instance. If one the sprue is close to the margin it's better not to touch it.

Close out of the Free-form step. Then right click on the printing base and choose "Save to file". In the dropdown choose .stl and save it to the patients folder, so you have everything in one place.

Printing

Now load the exported .stl into the printing software. It should load flat on the printing platform. Leave it like that; no need for any supports.

Asiga composer is great since you can do multi range prints. This means that different parts of the object will print at different layer heights, speeding up the print where quality is not needed.

In this case, we can do multi range print for the first 5 mm this by clicking the "Add range" button, modifying the "Print Range To" value to 5 mm and "Slice Thickness" to 0,1 mm (100 microns). The second range will automatically adjust it's starting range where the first one ends. You might want to play with the "Print Range To" value to position it between the crowns and the sprues.