finaddictfred,
Yes, this has been answered before but it never hurts to mention it again.
I'm assuming you are referring to full or complete dentures...i.e., no natural teeth=edentulous.
The official line is that you should not dive with them because they are an aspiration hazzard. The lower denture is usually unstable because it can be moved by the tongue and the muscles of the cheeks and lips. The upper denture is more stable but when you inhale through the regulator, the air rushes past the palate portion of the denture between the tongue and denture and creates a low pressure area (relative to the pressure between the denture and the hard palate. This is an example of Bernoull's Principle. The denture can theoretically be sucked away from the palate and into the air stream...forcing it back into the throat.
The "unofficial" line is that I have no knowledge of any scuba deaths related to denture aspiration. It seems that most scuba divers with dentures wear them during dives. They are used to them and can sense when they are coming loose. It certainly seems easier (to me) to hold the regulator in the mouth.
If you dive without your dentures, you will probably need to use the Manta mouthpiece or the ComfoBite. Neither requires teeth to hold them in place.
Removable partial dentures are usually well anchored and shouldn't be a problem...with the exception of a one toothed or Nesbitt partial denture. These are rather small with one or two sharp metal clasps. Should one of these babies escape, not only might they be aspirated, the metal clasps may make removal difficult to impossible.
Some words of warning though...
.....You might want to keep a spare or duplicate denture handy...especially the upper. If you lose you denture underwater, you won't be looking to pretty when you surface. The probability is directly proportional to how far away from home you are, the cost of the denture and the cost of your dive trip....Murphy's Law, denture corollary.
Biting on the bite tabs with a denture might break the denture...see my advice in the last paragraph.
Consider the use of a denture adhesive even if you normally don't need one.
Now, enjoy your diving! Contact me if you have any questions.
DandyDon...now I know why you look so purdy!
Laurence Stein, DDS