ScanLoupe/Guides/exocad

Get a 3Shape .dcm into exocad

exocad has no reader for the 3Shape format, so the file has to become an STL first. The conversion is the easy part. The thing to watch is the scale.

The steps

1. Convert. Open the .dcm in the converter and save it as STL. Keep the case name on the file so it does not get lost among the others.
2. Check it looks right. Look at the arch on screen before you import. A scan that opens as noise or as a flat sheet is a bad conversion, and it is cheaper to spot it now.
3. Import into exocad. In the case, load the STL as the scan for the relevant jaw. exocad treats STL units as millimetres, which is what the file already carries.
4. Sanity check the size. Measure something you know, for example the width across the arch. A full arch usually lands somewhere near 50 to 65 mm. If you are out by a factor of ten or a thousand, something rescaled the mesh.

Why the scale usually survives

Vertices inside a 3Shape .dcm are stored as plain millimetre values. STL has no unit field at all, so every STL is just numbers and the reader decides what they mean. exocad decides millimetres. So a conversion that copies the numbers straight across lands at the right size with no adjustment.

That also explains the classic failure. Any tool that "helpfully" converts units, usually because it assumed inches or metres, throws the model off by a fixed factor. Nothing is wrong with the scan and nothing needs fixing in exocad. The conversion step was wrong.

STL or PLY

	STL	PLY
Geometry	Yes	Yes
Scan colour	No	Yes, one colour per vertex
Use it for	Design work in exocad	Looking at the case, or showing the practice

For design, STL is the right answer and the missing colour costs you nothing. PLY is worth having when the scan carries colour and you want to keep it, for example when you are pointing out a preparation margin to the practice.

The same file in other software

• Meshmixer and Blender. Both import STL and PLY. Blender treats one blender unit as one metre by default, so a millimetre scan looks tiny until you set the scene scale or zoom in. The mesh is fine.
• Printer and slicer software. Nearly all of it takes STL in millimetres, which is exactly what comes out of the conversion.
• Other design suites. If it takes an STL scan, it takes this one. There is nothing 3Shape specific left in the file after conversion.

Questions

Can exocad open a .dcm directly?

No. exocad imports STL and PLY and has no reader for the 3Shape HPS format inside a .dcm. Convert to STL first.

Will the model come in at the right size?

Yes, if nothing rescaled it. The scan is stored in millimetres and exocad reads STL as millimetres, so a correct conversion needs no adjustment.

Should I use STL or PLY?

STL for design work. PLY when you want to keep the scan colours, because PLY stores a colour per vertex and 3Shape scans often carry them.

Does the scan need repairing after conversion?

Usually not. The conversion copies the existing mesh rather than rebuilding it. Nothing is smoothed or decimated, so holes in the STL were holes in the original scan.