Can people with artificial teeth (dentures) do OP?
Yes. People with artificial teeth (dentures) can do OP without the dentures. Do slowly so that oil does not escape through lips. If you do OP with dentures, they become loose in between and OP will not be effective.
Should we practice OP for 15-20 minutes only or is it alright if we do for 10 minutes as it is difficult to keep oil in the mouth for such a long time? Would it be better if pulling is done for more than 20 minutes?
The most important thing is the oil should become thin and white like milk. This happens in 15-20 minutes in most cases. If the oil has not become thin and white, you did not work it sufficiently long. Pulling effect is and optimum if it is done for 15-20 minutes. Less time may mean it is not sufficient time to be effective and much more time is wasteful effort. However, if mouth is full earlier you may spit it out.