In case anyone's interested in seeing what I need to do to clean up the geometry.
The teeth gaps that still looks messy (to the left) has the whole inner edge separated, so it registers as unconnected. The issue comes from when I cut out that grill box shape on the inside of the face mask. I had missed a setting, so it didn't fuse the cut into the model, but kept the new shape as a separate piece.
Thankfully the other facemask's didn't have this issue.
And since I have to mess with every single polygon anyway... there's no reason not to simplify and clean things up. It will also remove size on the file. I couldn't use optimize or automatic tools, as that screwed up the shapes, so I'm doing things manually, fixing one polygon at a time. Which is fairly time-consuming.
