The fact that you can use Efferdent to clean them.
Most dentures are made from porcelain, a type of ceramic or they are made of resin, a very hard plastic. Hence this product lends itself to the bong and pipe cleaning world.
I tried this technique on a glass spoon pipe. I put the pipe in a ziploc freezer bag with the efferdent and some water.
The magic started when the bubbles kicked in and cleansing began. Tiny Bubbles of Cleaning Goodness
It only took a few minutes for the bubbles to fizzle out and then I kinda let it marinate. After pulling the pipe out of that now nasty ziplock, I had to touch up a couple of areas with a q-tip. Gunk came of real easy though. I rinsed the piece real well and she was as good as the day we met.
Although I haven’t tried it, I could see this working well on a lot of bongs.
Note: If the resin was old, I could see having to do this a couple times.