Flexible Filament or Resin Safe for Use in Mouth

Hi!
I'm new to this and educating myself quickly over the last few weeks. I want to prototype an idea I have for something that would fit in a person's mouth. I'd need it to be somewhat flexible or rubber-like but obviously also biocompatible (non-toxic, non-latex, non-bpa etc). I'm not sure what people who print mouhtguards make them out of now and I haven't yet found a lot of specific info online. I turn to you.

I'm not yet sure what kind of machine I'm going to be working with. It seems most companies that do dental work are using SLA machines but I'll go a cheaper route if I can initially. There's going to be a lot of iterating for a while. So I'm going to determine the most appropriate and easy to use/modify end-material and work backwards to the printer type and ultimate purchase decision. Is there a flaw in that logic?

Thank you for any and all input you may have!
Philip

there is an italian company who make human friendly flexible filament.
http://www.mymatsolutions.com/

As far as I know those are the only certified flexibles around.
Either the Foodie or C4-U would be suitable - not sure what the difference is.
Both can also be boiled, sterilised in an autoclave etc.

The dental stuff made on resin machines is not usually destined directly for people's mouths. More often they are moulds, jigs or reproductions for fitting braces etc.

If anyone does end use flexible filament it will be Envisiontec: https://envisiontec.com/3d-printing-materials/
Looking thorugh their - end use section I can't find anything that's food grade.

Thank you CA! Do you have any sense of what the makers of printed mouth guards are using? I can't seem to find info on that. That would essentially be exactly what I'm looking for. Enivisiontec seems like a major player in the dental arena but their machines are super duper expensive. Wondering if their biocompatible resins are usable in other SLA or DLP machines. My quest continues.