hello and welcome to HCM forum,
I will be glad to answer your query,
First of all, I would like to inform you that these signs and symptoms are after effects of Radiotherapy and chemotherapy
and pain is from dry mouth
, I would like to advise you to let him see a dentist
as the dentist will prescribe him saliva substitutes.
Intake of oral medications usually aggravate dry mouth ,therefore we have to supplement salivary substitutes in order to treat all the oral conditions.
I hope this answer was useful,
i wish you and your family a very good health,