Microplastics shouldn’t make the list of things to worry about here.

For one, we don’t really know how/why microplastics are bad, or how bad. If they have significant bad effects, the mechanism is slow and subtle, so unlikely to affect dogs (who, very sadly, just don’t live that long).

Second, the incremental increase in microplastics from this device would be very tiny compared to typical exposure estimates.

When you balance the very small risk against a tangible benefit, they answer is clear.

If it is, we should probably start by worrying about chew toys.

I wouldn't worry about that, but about bacteria colonies inside the print. Sure dogs already eat random (and literal) shit, but if it's placed on an already inflammation prone nose, maybe it should be a some special material. Bacteria don't grow on metals, maybe it can be some silver ion filament or maybe at least solid resin

Dogs likely don't live long enough for microplastics to be a big problem. We haven't seen an increase in cancers in dogs in recent years like we have with people.

They're main exposure to microplastics would be from toys, water, dishes, and low-quality food, anyway. This nose guard would be a small drop in the bucket.