Hi.. Can understand your concern.. As per your complain cough and vomiting sensation in a patient who is wearing a new denture but is not used to it as you said that she is wearing denture for three decades.. It is very clear from it that she does not have a problem of Gag reflex and she can tolerate the denture well.. The reason which is causing her the discomfort can be that her new denture must be over-extended deep onto the soft palate and any movement like the normal swallowing of the saliva also leads to stimulation of the sensitive soft palate and can lead to coughing and vomiting feeling.. The extension at the palatal end should also be checked for thickness as very thick margins also lead to discomfort. One reason can be that if the denture is not fitting well and it moves with slight movement of the mouth this also leads to palatal stimulation and gagging.. Any space between the denture surface and the surface of palate can lead to food debris accumulation and loosening of denture and it can cause discomfort.. In case if she is using any denture adhesive and if it does not suit the body there are chances that it can also cause the above explained symptoms.. I would suggest you to consult the dentist and explain the immediate symptoms and get checked for the extensions and thinning and reducing the extent of the extensions or change in adhesive can provide her relief from the symptoms.. Hope this information helps.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.