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I have a tooth and a nerve inside it as two different objects.

The first picture is a molar tooth and the second image is a nerve inside the molar tooth.

My question is; how to generate supports so that the nerve inside the molar tooth will be printed out? (3D printing object inside another object)

The purpose of the aim is to use the printed object as patient education material. (Not for sale)

3D model of a molar

3D model of a nerve inside of a molar

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    $\begingroup$ How would the patient see the nerve if it is inside the tooth? $\endgroup$
    – 0scar
    Nov 24, 2023 at 23:44
  • $\begingroup$ @Oscar, molar tooth as transparent pla and nerve as Red pla $\endgroup$ Nov 25, 2023 at 6:09
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    $\begingroup$ Transparent is usually not so transparant as you wish considering using FDM as you used tag PrusaSlicer. Furthermore, do you a have printer that can print multiple colors? Please update your question by edit to include the printer make and model. $\endgroup$
    – 0scar
    Nov 25, 2023 at 8:51

4 Answers 4

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With great difficulty

Problems

From your tags, it looks like you want to use FDM process. Unless you have mastered How To Print Glass technique, you can forget about the inside model being visible in the outside one. Even if you did, I have never seen anyone manage to make it work with multicolor / multimaterial printers. That is, if you even have one, most of the people do not.

The best translucency I was able to get using FDM is this: Photo of a sample

Printing two models separately and making them fit perfectly is another can of worms. Printers have limited accuracy. Materials have shrinkage that is different in different colors, if ever so slightly.

My solution

Print one transparent part, with a hole in the shape of the inside part. Then, fill it with UV resin or paint. If possible, use transparent resin instead of FDM - you will get good enough transparency without a need to tune your printer and polish surfaces.

That's not something I have tried, but indeed something I planned*.


* printing TransparentTestPart_0.12mm_PETG_MK3S_50m.gcode now, as I write this answer.

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    $\begingroup$ Best I've ever seen is posted here: learn.colorfabb.com/lets-make-something-clear Note that my own experience produced exactly the same translucent (not transparent) parts you also produced! :-) $\endgroup$
    – 0scar
    Nov 29, 2023 at 14:52
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Similar to the answer above, but with a bit of a twist, it may be simpler to print both parts out as molds, and then to cast the parts that you want in two-part casting resin.

There are various tutorials on the internet that go into detail on how to do this.

For example: 3D Printed Molds Tutorial: How to DIY Your Own

Cura slicer even has a function for this. Mold mode though I've never used it.

Use a Boolean function to create a cavity inside the tooth using the nerve as a cutter, and then export it. Then use Cura's mold function to create a mold of the tooth with the cavity inside it.

Create a resin tooth using clear resin, and then once that is set mix up some red resin and pour it into the cavity.

It's still using 3D printing, just not as you originally thought. IT may be easiest to do the tooth mold in two parts and then join them together.

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Transparency is interesting, but maybe one of the following options, for the purpose of inspiration, is more achievable:

An anatomical model

A model consisting of different parts that can be taken apart for demonstration. Printed or painted in multiple colors. Such as:

Photo of an anatomical model of a molar tooth with caries

Source: Mentone Educational

A cross-sectional model

A model that is cut in half, showing the insides. If printed in the right orientation, multi-color prints can, to some extent, be achieved by changing the colors at a certain layer, or by painting. Such as:

A 3D model of tooth anatomy

Source: Free3D

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    $\begingroup$ +1 Although not really an answer to the question (considering the comments), the answer does provide an alternative solution. I think I would prefer such a print if I'm at the dentsit as this is more close to the real molar. With about 4 colors and some STL editing skills you'd be able to reproduce the molar from the first photo! $\endgroup$
    – 0scar
    Nov 29, 2023 at 14:57
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You can accomplish this with a multiple extruder 3D printer.

You'll have one extruder print in transparent and another in red. However, you'll also need a third extruder to print "soluble" supports.

When you print with soluble supports, there are extra columns used to secure partly "floating" objects like the red nerve during the 3D printing process. After the print is done, you drop the 3D print in water. The soluble supports dissolve away, leaving just the nerve and the tooth.

Soluble supports and multi-extrusion printing are how you would print something like this. I'm not sure if you'll go through the effort to do it, but it can be done.

I have no experience with transparent filament though, it looks like by the other answers it's not very good.

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    $\begingroup$ The red nerve is printed inside the molar cavity, so how would you get water in the cavity to dissolve the support? Furthermore, soluble support sounds amazing, but having used it for a while, my personal opinion is to avoid it. $\endgroup$
    – 0scar
    Dec 9, 2023 at 7:55
  • $\begingroup$ Ahh i wasnt aware that it was totally enclosed. And yes, now that you mention it, my few tries with citric acid soluble support never dissolved 100%, it more just made it easier to remove the supports. I never tried the water soluble one tho - went back to just single extruder printing after that $\endgroup$
    – K Mmmm
    Dec 9, 2023 at 13:55

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