Depends on the nature and extent of the repair. Cyanoacrylate doesn't bond that well with Vulcanite, so unless the fix is a small one and/or the area to be fixed has a taper in the center of the depression and is wider at the top and the bottom, the patch will eventually fall out at some point.I got some black rods from Tap Plastics and filed a bit down to powder. I filled the tooth marks with the filings and super glue. Then I sanded down and polished with micromesh and Novus plastic polish (3 steps). I did 2 stems this way I and I can't see the repair with 10x loupe. YMMV
I wonder now if I need the filed down fills at all.
The most recent repair I used black colored rubberized super glue. I think I got it from Harbor Freight. That did not blend so well and I can see the repair spots. It may work better on a vulcanite stem.