Hello. Did your dentist ask you to swallow while observing your throat?
You appear to be offline, so I will leave a possible answer. Post-polio syndrome (PPS) can develop decades after one's original polio episode. Many PPS patients complain of swallowing difficulty or food getting stuck in their throats, symptoms believed to be related to nerve overuse and/or muscle weakness. Your dentist may have been checking for evidence of muscle weakness or food trapping. Here is a useful reference from 2010 based on U.S. PPS patient care: http://www.post-polio.org/edu/pphnews/PPH26-3sum10p6-9.pdf